Garyounis Scientific Bulletin Special Issue #5 (2008) by Noel Boaz

Garyounis Scientific Bulletin A Publication of the Research Centre

Special Issue

No. 5 2008

Circum-Mediterranean Geology and Biotic Evolution During the Neogene Period: The Perspective from Libya Edited by N.T. Boaz, A. El-Arnauti, P. Pavlakis, and M.J. Salem

University of Garyounis Benghazi, G.S.P.L.A.J

Cover photograph: Reconstruction of the Messinian-aged canyon of the ancient As Sahabi River as it enters the Mediterranean Sea, viewed from the southeast. The current coastline of the Sirt basin is shown in outline. From Carlo Nicolai "Tracing the As Sahabi Channel System in the Ajdabiya Trough, Central Sirt Basin, Libya" ÂŠ Shell Exploration and Production Libya GmbH 2008. Shell Exploration and Production Libya GmbH is a major sponsor of the East Libya Neogene Research Project. University of Garyounis Research Centre P.O. Box 9521 Benghazi, G.S.P.L.A.J. ÂŠ University of Garyounis Libyan ISBN National Agency National Library of Libya, Benghazi

Printed by Gutenberg Press, Ltd., Malta

GARYOUNIS SCIENTIFIC BULLETIN, 2008

Special Issue, No. 5

Circum-Mediterranean Geology and Biotic Evolution During the Neogene Period: The Perspective from Libya

GARYOUNIS SCIENTIFIC BULLETIN Special Issue Number 5, 2008

Edited by N.T. Boaz, A. El-Arnauti, P. Pavlakis, and M.J. Salem

Volume Dedicated to Abdul Wahid Gaziry

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TABLE OF CONTENTS

DEDICATION ……………………………………………………….……..…iv FOREWORD — A. Said Ali ………………………………………......…...….v WELCOME ADDRESS — M. Dermitzakis ……………………………..…......vi INTRODUCTION ……………………………………………………...…........ix HISTORY AND METHODOLOGY A Brief History of As Sahabi Research and Collections — N.T. Boaz, A. El-Arnauti, and P. Pavlakis………………..….……..1 The Discovery of the As Sahabi Site: Ardito Desio or Carlo Petrocchi? — L. Rook…………………………….....…....13 GEOLOGY The Pre-Messinian Miocene Stratigraphy and Sedimentation in the Marada-Zaltan Area, Central Sirt Basin, Libya — A. S. El-Hawat……………………………..……….…………….…21 A Contribution to the Stratigraphy of Formations of the As Sahabi Area, Sirt Basin, Libya — A. M. Muftah, F. M. Salloum, M. H. El-Shawaihdi, and M. S. Al-Faitouri………...33 Biostratigraphical Notes on the As Sahabi Stratigraphic Boreholes 1 and 2, Sirt Basin, Libya — A. M. Muftah, A. A. El-Mehaghag, and S. Starkie ……………………………….….47 Establishment of a Chronostratigraphical Framework for the As Sahabi Sequence in Northeast Libya — C. Beyer ........................59 The Wadi Al-Farigh Member of the Sahabi Formation — M. Shawaihdi and T. Al Trabelci ………………………………......71 Tracing the As Sahabi Channel System in the Ajdabiya Trough, Central Sirt Basin — C. Nicolai ……………………………….….....85 The Development, Decline and Demise of the As Sahabi River System over the Last Seven Million Years — N. A. Drake, A. S. El-Hawat, and M. J. Salem …………..….…...95 BIOTIC EVOLUTION New Remains of Crocodylus checchiai Maccagno 1947 (Crocodylia, Crocodylidae) from the Late Miocene of As Sahabi, Libya — M. Delfino………………………………...111 Overview of the Fossil Avian Fauna from As Sahabi – D. Michailidis…....119 The Age of the Small Mammal Faunas from Jabal Zaltan, Libya — W. Wessels, O. Fejfar, P. Peláez-Campomanes, A. van der Meulen, H. de Bruijn, and A. El-Arnauti……….……….129

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New Data on the Rodent Fauna from As Sahabi, Libya — J. Agustí ……..….139 Peri-Messinian Dwarfing in Mediterranean Metaxytherium (Mammalia, Sirenia): Evidence of Habitat Degradation Related to the Messinian Salinity Crisis — G. Bianucci, G. Carone, D. P. Domning, W. Landini, L. Rook, and S. Sorbi ...............................145 Revisiting As Sahabi Equid Species Diversity, Biogeographic Patterns, and Dietary Preferences — R. L. Bernor, T. M. Kaiser, and D. Wolf ...159 Systematics and Biogeographic Relationships of As Sahabi Suidae — G. Gallai, R. L. Bernor, and L. Rook ………………………………….169 Rediscovered Hippopotamid Remains from As Sahabi — P. Pavlakis………………………..………………………………….....179 Newly Discovered Remains of As Sahabi Anthracotheriidae — P. Pavlakis and N. T. Boaz………………………………………..........189 New Records of Bovidae from the Sahabi Formation — A. W. Gentry .……..205 Review of Fossil Proboscidea from the Early-Middle Miocene Site of Jabal Zaltan, Libya — W. J. Sanders …………………….……217 Review of Fossil Proboscidea from the Late Miocene-Early Pliocene Site of As Sahabi, Libya — W. J. Sanders ……………………..……...241 An Overview of the As Sahabi Carnivore Guild with Description of New Specimens from ELNRP Field Surveys — L. Rook and R. Sardella ……………………………………………….………...257 New Fossil Cercopithecoids from the Late Miocene of As Sahabi, Libya — B. R. Benefit, M. McCrossin, N.T. Boaz, and P. Pavlakis ......265 A Current View of As Sahabi Large Mammal Biogeographic Relationships — R. L. Bernor and L. Rook …………………………...283 A View to the South: Eo-Sahabi Palaeoenvironments Compared and Implications for Hominid Origins in Neogene North Africa — N. T. Boaz ………….……………………291

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Abdel Wahid Gaziry (20 December, 1941 – 13 January, 1989) The long interlude between the end of the field researches of the International Sahabi Research Project in 1981 and the inception of new research by the East Libya Neogene Research Project in 2005 saw the untimely death of Libya’s pre-eminent vertebrate paleontologist, Abdel Wahid Gaziry. He was a founding director of the research at As Sahabi, worked tirelessly for the betterment of earth science research and teaching in the institution at which he spent his career, the University of Garyounis, and was a close friend and colleague to all who knew him. Abdel Wahid’s passion for palaeontology, especially for his prized proboscideans, was infectious, and his energy and enthusiasm kept the field team working in spite of the vicissitudes and daunting challenges of the Sahara Desert. He strongly believed in the need to connect two of Libya’s most important fossil sites, As Sahabi and Jabal Zaltan, based on his comparative studies of proboscideans. He would be proud that the East Libya Neogene Research Project has been established to do just that. This volume includes revised and expanded papers presented at a 1995 symposium held at the University of Garyounis in Benghazi, Libya in honour of Abdel Wahid Gaziry. This volume is also dedicated to his memory. The Editors

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Foreword The Research Centre of the University of Garyounis supported the International Sahabi Research Project from its inception to yield impressive results through the years. Scientific contributions from this project were published in a special volume of our Garyounis Scientific Bulletin in 1982. We present here another special issue of the Garyounis Scientific Bulletin to include recent field and laboratory results of the East Libya Neogene Research Project at the fossil sites of As Sahabi and Jabal Zaltan, Libya, in addition to papers presented in diverse meetings on the same subject held in Benghazi and elsewhere. The Research Centre intends to continue facilitating this research not only at the tremendously important fossil site of As Sahabi but also at Jabal Zaltan and other related areas to help the participating scientists in fulfilling the goal of discovery and analysis of different aspects of palaeontology, geology, and the palaeoenvironment.

Dr. Ali Said Ali Director of the Research Centre, University of Garyounis

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Welcome Address The Contribution of Vertebrate Palaeontology in Modern Stratigraphy M.D. DERMITZAKIS Stratigraphy is an essential and dynamic discipline in modern geology. As our understanding of global processes accelerates, there is a clear and increasing demand for high-resolution stratigraphical data. In recent years this has led to the development of a bewildering array of specialists, and increasingly sophisticated, analytical tools. Despite this, the fundamental aims of stratigraphy remain unchanged: those of establishing the sequence of rock units and then interpreting them as events in earth history. The initial recognition of lithostratigraphical units and the determination of their relative chronology are insufficient for correlation with either other units in adjacent regions, or with the Global Chronostratigraphical Scale. Traditionally, biostratigraphy has provided the basis for most correlations, and is still the most important method of correlation with the Global Standard Stratigraphy. Modern biostratigraphy relies intimately on a biological understanding of

fossils. Although quantitative studies are becoming increasingly common, most biostratigraphy still relies simply on presence/absence data for particular fossil taxa. Fossils provide an important interpretative tool, as, using uniformitarian principles, it is possible to reconstruct ancient ecologies and to extrapolate the ecological tolerances of living to fossil organisms. The palaeontological and stratigraphical community has already launched a broad interdisciplinary and process-oriented analysis of the interactions between life and Earth through geological time. Scientists wish to understand the patterns and process of evolution that gave rise to the biological diversity that surrounds us today. They also wish to obtain a better understanding of how past changes in the biota have resulted from and impacted on the global environment. The fact that life has been a major forcing factor in the development of the Earth system places those

M. Dermitzakis, Faculty of Geology & Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece

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Aegean, that contributed to the arrival of a large number of Asian steppe and African animals. At about 10 million years ago, the first hipparion-like horses appeared in the Old World. These horses crossed the Bering Strait near the time of sea level lowering, at or near the Middle-Late Miocene transition and underwent rapid dispersal. The reason for the great success of Hipparion might be the fact that they found no real competitor in Eurasia as Anchitherium, the other early relative of the horse, lived in the forest and not on the plains. During the Vallesian and Turolian more species came from North America. The fauna and flora of Greece during the Turolian, the period between 9 to 5 ma, is common in a huge area extending from Spain to China. Turolian faunas are known from many sites of Greece, such as Maramena (Makedonia), Pikermi (Attika) and what is now the island of Samos (part of the mainland during the Miocene). Typical representatives are hyaenas, the tree-toed horse Hipparion, the bovid Tragoportax, Machairodus, gazelles, and the early deer Pliocervus. The climate was warm, and was similar to that of India today. The most famous Turolian locality in Greece is Pikermi. The locality became famous at the beginning of the 19th century, not only for the huge amount of fossils that were excavated, but also because it was in Pikermi that for the first time scientists discovered that ancient faunas were completely different from extant faunas. Pikermi actually represents the starting point of modern palaeontology. On the other hand the famous Libyan fossiliferous site As Sahabi represents a latest Miocene/earliest Pliocene

who have studied the geological history of life in a strong position to lead this endeavor. In order to achieve this, palaeontologists must collaborate with the biological community in determining the evolutionary tree of all life. Palaeontological data are necessary in order to resolve and calibrate phylogenetic trees and understand the history of ecosystems. We must move more fully toward a quantitative characterization of the history of life, drawing upon a synthesis of phylogeny and quantitative morphology for important biological groups, within a wellconstrained, quantitatively-based, temporal framework. In particular, Vertebrate Paleontology, which in the past was mainly involved with systematics, can contribute to subjects that concern mankind today, such as drastic reductions in terrestrial biodiversity as habitats are reduced or altered by human activities. The geological history of terrestrial ecosystems is an important topic for both biologists and earth scientists, who are involved with the problem of environmental fragmentation versus biodiversity. Therefore, the investigation of changes in terrestrial ecosystems during the closest geological past â&#x20AC;&#x201D; mainly the Neogene â&#x20AC;&#x201D; a time interval that has witnessed enormous geographical and environmental changes, represents one of the main stratigraphical and palaeontological research aspects, as it allows us to understand the past floral and faunal change by reference to present day ecosystems. During the Messinian (5-6 million years ago), an archipelago was formed in the place of the old mainland of the vii

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change, collapse, and recovery. I am very happy to welcome all of you to the â&#x20AC;&#x153;Research Conference on EuroAfrican Biotic Evolution in the Neogene,â&#x20AC;? confident that the essential and frank discussions which take place these days will produce unique outcomes and promote scientific collaboration between Libya and Greece. I wish you all a successful and fruitful workshop.

vertebrate fauna from Libya. It includes a mixture of Eurasian and African vertebrates, and as such it is important for biogeographic reconstruction and palaeoecologic comparisons. The As Sahabi fauna as a whole supports a biogeographic connection with Subparatethyan Pikermian faunas and the hipparion data further support both the Pikermian connection as well as a Siwalik-East African connection. The study of the As Sahabi site has and still will produce results with implications for the systematic biology, geochronology, palaeogeography, palaeoclimatology, palaeontology and palaeoanthropology of the Old World Neogene . For these reasons, a joined attempt to simultaneously examine terrestrial ecosystems such as Pikermi and As Sahabi, in the framework of a new generation of spatial and temporal reconstructions, will lead to the study of the temporal and spatial palaeoecological patterns of mammal communities in the context of ranked changes in palaeogeography and palaeoenvironmental/pa laeoclimatic aspects. These efforts will lead to a better understanding of the dynamics and sensitivity of both important terrestrial ecosystems and the dynamics of mammal biodiversity in terms of the response to locally, regionally, or globally-induced environmental perturbations. The integration of data and the relevant interpretations are expected to result in a better understanding of the episodes of major biotic change during the Neogene, in order to put geological and palaeontological constraints on the modeling and prediction of ecosystem

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Introduction

This volume reports new results from field and laboratory research of the East Libya Neogene Research Project at the fossil sites of As Sahabi and Jabal Zaltan, Libya. It also is a compilation of papers originally presented at two meetings held eleven years apart, the 1995 symposium “Biotic Events of the Circum-Mediterranean Messinian” held at the University of Garyounis, Ben-

ghazi, Libya, and a research conference and workshop “Euro-African Biotic Evolution in the Neogene” held November 23-24, 2006 at the University of Athens, Greece. Unavoidable logistic difficulties occasioned by geopolitical circumstances delayed the completion of the proceedings of the former conference. But this delay had a salutary effect as well in allowing new data collected in

Figure 1. Participants in the “International Conference on the Biotic and Climatic Effects of the Messinian Event in the Circum-Mediterranean” held at the Islamic Call Society Conference Center, Benghazi, January, 1995

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Figure 2. Participants at the research conference and workshop “Euro-African Biotic Evolution in the Neogene,” November 24, 2006, National and Kapodistrian University of Athens, Greece. Left-right, front row: Angeliki Efstathiou, Jordi Agusti, Constantinos Doukas; second row: Fathi Salloum, Dimitris Michailidis, Raymonde Bonnefille, Mohammed Al-Faitouri, Paris Pavlakis, Noel Boaz, Brenda Benefit, Alexandra Vandergeer; third row: Nick Drake, Wilma Wessels, Ahmed El-Hawat, Socratis Rouseakis, Muftah Shawaihdi, Monte McCrosssin. Not pictured: Silvia Sorbi, George Theodorou, and Michail Dermizakis.

sin, focusing on the Libyan fossil sites of As-Sahabi and Jabal Zaltan. Papers, including comparative and regional studies, are authored by members of the East Libya Neogene Research Project, a joint coordination of the International Institute for Human Evolutionary Research (U.S.A.) and the University of Garyounis (Libya). Many international institutions have participated in the research through the activities of their involved faculty and staff, but we acknowledge particularly the contributions of the University of Athens (Greece), New Mexico State University (U.S.A.), and University of Firenze (Italy). Papers are organized into three sections. An initial section on history of research and methodology contains two papers and presents some of the history behind the investigations in eastern Libyan palaeontology and geology, the current palaeontological research method-

the interim to be included, resulting , we hope, in mature and well considered interpretations in the present volume. This special issue of the Garyounis Scientific Bulletin represents a reinauguration of a formerly active journal published by Libya’s oldest university. We are pleased that the East Libya Neogene Research Project could contribute to this worthy goal of re-establishing an important outlet for scientific research in Libya. We thank the Research Centre of Garyounis University and its Director, Dr. Ali Said Ali, for their invaluable support in publishing this volume. Dr. Mahmoud Fadiel, former Dean of the Faculty of Science, is thanked for his support. This volume presents an overview of the current state of knowledge of the Middle Miocene to Messinian-aged geology and palaeontology of Africa and Eurasia bounding the Mediterranean Ba-

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INTRODUCTION

time the last 200 km of its course to the sea (see cover). Nicolai also found evidence of infilling and incisional episodes suggestive of a longer and perhaps more complex intraMessinian history of deposition. The Eo-Sahabi River separated the eastern, largely later sedimentary deposits from the western, and earlier Marada Formation deposits of Jabal Zaltan. Both of these areas are encompassed in the study area of the East Libya Neogene Research Project, and in fact the sedimentary environments, comprising fluviatile, estuarine, lagoonal, and shallow near-shore marine depositional environments, are similar between the two areas. Future comparative and correlational studies between As Sahabi and Jabal Zaltan will be informative for both geological and palaeontological research. As Sahabi and Jabal Zaltan are among the most important Old World Neogene fossil sites. The largest section of this volume, including 16 papers, presents the most recent research now being undertaken by the East Libya Neogene Research Project, coupled with comparative studies. Particularly noteworthy are new taxa of small mammals discovered at Jabal Zaltan (Wessels, et al., this volume), a new species of cercopithecoid at Sahabi (see Benefit, et al., this volume), a new cranial specimen of anthracothere at Sahabi confirming this animalâ&#x20AC;&#x2122;s unique dental formula of five premolars (Pavlakis and Boaz, this volume), and the first dental remains of the As Sahabi antelope species Miotragoceros cyrenaicus (Gentry, this

ologies employed, and the status and whereabouts of the collections for future study by other scientists. The second section contains six papers on geology. This section details the significant new discoveries related to the geological contexts of As Sahabi and Jabal Zaltan. The East Libya Neogene Research Project has just begun renewed research at the latter site. El-Hawat who pioneered modern geological investigations of the Marada Formation, provides us with an overview of current knowledge of the sediments and facies. Muftah, et al. present a similarly useful overview of the Sahabi Formation. New dating results for the sedimentary formations at As Sahabi are reported in a separate paper by Muftah and colleagues and by Beyer. The ELNRP will build on these significant results as work proceeds. Shawaidhiâ&#x20AC;&#x2122;s paper on the Wadi Al Farigh Member is an important contribution to our understanding of the barrier formations and lagoonal facies of the Sahabi Formation. Two papers bear importantly on the course of the ancient As Sahabi River. This was a major water course of Neogene Africa, rivalling in competence the Nile, Niger, and Congo Rivers, as judged by satellite imagery of the size and extent of its drainage network (see Drake, et al., this volume) and the depth of its downcutting during the Messinian Event (see Nicolai, this volume). Using newly contributed seismic data from Shell Exploration and Production, Libya, Nicolai also is able to visualise for the first

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(1992) attempted to resolve the theninterpreted lithostratigraphic evidence for a post-Messinian age of the Sahabi Formation and the biostratigraphic evidence for a preMessinian age by noting endemic elements, such as the anthracothere (Libycosaurus petrocchii), in a relatively isolated northern African paleozoogeographic. Pending new analyses from As Sahabi, Boaz, et al. (2008) re-affirmed that a Late Miocene age was the best estimate on comparative biostratigraphic grounds for the age of this fauna. Resolving these issues of age is a major priority for further research at As Sahabi and Beyerâ&#x20AC;&#x2122;s K-Ar dates on Formation M glauconites and his first magnetostratigraphic analysis from the Sahabi Formation reported in this volume are major steps in this direction. The sites of As Sahabi and Jabal Zaltan fit within a broader context of biotic evolution and exchange between Africa and Eurasia. A number of papers treat these themes, but those by Bernor and Rook and Boaz review comparative data from other regions and place the Libyan sites in a context of the Old World Neogene. As Sahabi has a particularly close resemblance to the Chadian site of Toros Menalla whkich has yielded the earliest remains of hominids. As windows into the Miocene, As Sahabi and Jabal Zaltan are just beginning to yield up a much fuller view of this time period, so important in understanding the origins and evolution of many animal groups, including our own. For valuable logistic support we thank AGOCO Benghazi and its former director, Fareg Said, for their support in hosting the 1995 Messinian conference in Benghazi. Sirt Oil and its General Director, Ali El Sogher, kindly provided vehicles and other support at various times for the project

volume). New remains of carnivores (Rook and Sardella), suids (Gallai, et al.), equids (Bernor, et al.), birds (Michailidis), and crocodilians (Delfino) are described. Overviews of the As Sahabi sirenians (Bianucci, et al.), proboscideans (Sanders), and micromammals (Agusti) provide synthetic treatments of these groups in the contact of circum-Mediterranean palaeoenvironments and biostratigraphy. Several papers describe for the first time fossils collected from As Sahabi in the 1930â&#x20AC;&#x2122;s which have been in the collections of the National Museum of Libya, Tripoli. Sanders reports on proboscideans, Pavlakis on hippopotamids, and Pavlakis and Boaz on anthracotheres. More study of these important collections in Tripoli, which also include undescribed fossil wood, chelonian, crocodilian, and cetacean specimens, will be needed in the future. Director of Archaeology, National Museum of Libya, Giuma Anag has been instrumental in facilitating these researches. The vertebrate studies provide important biostratigraphic age information. Wessels, et al. (this volume) assigns the small mammal fauna to between 14 and 19 ma, and divides it into three age zones from the late Early Miocene to the early Middle Miocene, based on grouped localities of collection. Sandersâ&#x20AC;&#x2122; paper on Zaltan proboscideans agrees with these age estimates and finds some evidence for an Early Miocene component among an overall assemblage of Middle Miocene age. The consensus of papers in this volume on the biostratigraphic age of the Sahabi Formation is a Late Miocene age, a position long championed by the late F. Clark Howell on the basis of his studies of As Sahabi carnivores. Rook and Sardella (this volume) agrees with this age assessment. Boaz

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Department, Fathi Salloum, for their consistent and much-valued support for the ELNRP. The research conference and workshop “Euro-African Biotic Evolution in the Neogene” held at the National and Kapodistrian University of Athens November 23-24, 2006 was sponsored by the Greek Ministry of Education, the Office of the President of the Greek Parliament, and the University itself. We thank then-Vice Rector Michail Dermitzakis, Honorary Chairman of the conference, for his support (see Dermitzakis, this volume). Vice Rector Ioannis Karakostas has added a new dimension to the work of the ELNRP with his signing and furtherance of inter-institutional cooperation between the University of Athens and University of Garyounis. Many individuals and organizations have contributed to the success of the research that is reported here. Field research was supported by U.S. National Science Foundation grants – BNS-0515591 to Brenda Benefit, Monte McCrossin, and Noel Boaz (New Mexico State University) and two grants from the NSF HOMINID-funded program “Revealing Human Origins Initiative (RHOI)” (grant BCS-0321893 to F.C. Howell and T.D. White, University of California, Berkeley) to Noel Boaz (International Institute for Human Evolutionary Research). Support for the As Sahabi research by the late Clark Howell and Tim White is gratefully acknowledged. A Ross University School of Medicine faculty research grant to Noel Boaz helped to support field database operations. AGOCO, Benghazi and Sirt Oil, Brega assisted in supporting the field seasons in 1997 and 1998 and the successful and wellattended Benghazi Messinian Conference in

and for the As Sahabi excursion during the East Libya Geological Symposium.. Shell Exploration and Production Libya is the principal corporate sponsor of the ELNRP and provided valuable support for the drilling project in April, 2007, reported on by Muftah, et al. in the current volume, as well as access to seismic data in reconstructing the Messinian Eo-Sahabi Channel (Nicolai, this volume). Shell Libya Exploration General Manager Marc Gerrits, and senior staff Alex Battaglia, Youssef Hamad, and Carlo Nicolai are thanked for productive ongoing collaboration between the ELNRP and Shell Libya. The contributions of Nicolai, Muftah, et al., and Shawaihdi in this volume would not have been possible without this important support. Boaz, et al. discuss some aspects of the future plans and prospects for subsurface drilling to be supported by Shell Libya. This collaboration will become increasingly important in future years as scientific results of the East Libya Neogene Research Project are published, collections are repatriated to Libya and stored, and results are prepared and presented to the public through museum exhibits and media. The University of Garyounis Research Centre was an important component of the As Sahabi research from its inception and we thank its present Director, Ali Said Ali, for his general support and for the funding of the printing and the realisation of this volume. The University of Garyounis hosted the 1995 Messinian conference in honour of Abdel Wahid Gaziry. We thank the University and acknowledge President of the University of Garyounis, Atiya Al-Faitouri, the Dean of the Faculty of Science, Mahmoud Fadiel, and the Head of the Earth Sciences

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Benefit, Monte McCrossin, Ahmed ElHawat, Fathi Salloum, Ahmed Muftah, Muftah El-Shawaihdi, Dimitris Michailidis, Mohamed Al Faitouri, and Naji Salini have formed the backbone of our planning and research teams in the field. Giuma Anag, Director of the Department of Archaeology, National Museum of Libya, has been a valuable partner in planning and facilitating the museological components of the project. Meleisa McDonell and Alan Almquist, board members of the International Institute for Human Evolutionary Research (ICSM), are thanked for their steadfast support. Ethimia Pavlakis is thanked for her invaluable help at many stages of the work. Field teams of the East Libya Neogene Research Project in 2006-7 carried flag number 93 of the Explorers Club, New York (see photos in Boaz, et al., this volume). This support of the Explorers Club is gratefully acknowledged. Finally, we thank and congratulate all the authors, who have weathered both the sandstorms of the Sahara and the evershifting winds of geopolitical change in order to accomplish so much. This volume came into being only through their commitment. Yet, much remains to be discovered, and we look forward to great progress in the coming years.

1995. The Great Manmade River Project, whose Area Manager in Ajdabiya, Khalifa El-Galbati, provided water and logistic assistance for the ELNRP, is thanked for their support. Condrill Benghazi has been invaluable in facilitating field operations, not only in respect to the logistically challenging borehole drilling operations, but in all aspects of vehicle, mobile camp, and travel arrangements for research personnel. General Manager Anders Nilsson, Operations Manager George Sayannos, and Lena Nilsson Sayannos are thanked for their many kindnesses and hospitality in Benghazi and Tripoli. Mujeeb Uddin of Condrill ably directed the technical aspects of drilling the As Sahabi boreholes in 2007. Our evolving knowledge of the remarkable fossil sites of As Sahabi and Jabal Zaltan has been compiled through the efforts of many individuals extending back over many years. The late Abdel Wahid Gaziry, to whom this volume is dedicated, pioneered modern palaeontological research in Libya. His work forms the bases on which papers by Sanders, Pavlakis, and Pavlakis and Boaz in the present volume are grounded. The late Jean de Heinzelin established with El-Arnauti the geological basis for all subsequent work. Clark Howell is fondly remembered as â&#x20AC;&#x153;grandfatherâ&#x20AC;? to the International Sahabi Research Project and we are pleased that the As Sahabi viverrid, Viverra howelli, was named in his honor (see Rook and Sardella, this volume). The late Remmert Daams undertook the first renewed field investigations at Jabal Zaltan when international travel restrictions prevented full teams from getting into the field. The contribution by Wessels, et al. (this volume) is based on this work. Brenda

The Editors, Noel T. Boaz, Ashland Ali El-Arnauti, Benghazi Paris P. Pavlakis, Athens Mustafa J. Salem, Tripoli

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A Brief History of As Sahabi Research and Collections

NOEL T. BOAZ, ALI EL-ARNAUTI, and PARIS PAVLAKIS

ABSTRACT Organised palaeontological fieldwork in the area of sedimentary outcrops surrounding the historic fort of Qasr as Sahabi has taken place during three periods of time: the mid to late 1930’s by Italian expeditions directed by Carlo Petrocchi, the late 1970’s to early 1980’s by the International Sahabi Research Project (ISRP), and current work under the auspices of the international East Libya Neogene Research Project (ELNRP). As Sahabi yielded to Petrocchi seven species new to science. Five species new to science have been discovered at As Sahabi since 1979. Initial fossil discoveries and most of the original 62 Petrocchi localities were in the vicinity of the As Sahabi fort. These localities in upper Members U and V of the Sahabi Formation have now been re-located, accurately positioned, and re-surveyed by the ELNRP. Original ISRP fossil localities were mainly located along the better exposed sediments to the west of the Sebkhat al Qunayyin, east and north of the As Sahabi fort, primarily in lower Member U of the Sahabi Formation. These spatial and stratigraphic differences between Petrocchi and ISRP localities account for observed differences in the two faunal assemblages. Ongoing geological research is aimed at elucidating the temporal and sedimentary facies variations that explain the differences in taxonomic make-up and evolutionary stages within the As Sahabi fauna. The historic initiation of drilled boreholes to elucidate the subsurface stratigraphy and the successful application of absolute geochronology are major steps in the research program of the ELNRP. Collections of fossils and geological samples from As Sahabi are housed at the Earth Sciences Museum of the University of Garyounis (ISRP and ELNRP) and at the Libyan National Museum (early Italian collections). Ongoing research at As Sahabi and Jabal Zaltan by the ELNRP will increase palaeontological collections and heighten the need for specialist training, making museum and university collaborations essential.

Noel T. Boaz, International Institute for Human Evolutionary Research, Integrative Centers for Science and Medicine, 2640 Takelma Way, Ashland, Oregon 97520, U.S.A., noeltboaz@integrativemedsci.org, and Department of Anatomy, Ross University School of Medicine, P.O. Box 266, Portsmouth Campus, Roseau, Commonwealth of Dominica, nboaz@rossmed.edu.dm Ali El-Arnauti, Department of Earth Sciences, Faculty of Science, University of Garyounis, Benghazi, Libya, alielarnauti@yahoo.com Paris Pavlakis, Department of Historical Geology – Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimioupoli Zografou, 157 84 Athens, Greece, pavlakis@geol.uoa.gr

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specialists discovered by the expeditions led by Carlo Petrocchi at As Sahabi.

Palaeontological investigations near the fort of Qasr As Sahabi were begun in the late 1920’s or early 1930’s by Ardito Desio and fully developed by Carlo Petrocchi and colleagues between 1932 and 1937 (see Rook’s following article in this volume). Petrocchi was the first director of the Libyan Museum of Natural History, founded within the confines of the historic Saray al-Hamra fort in Tripoli harbor. Today the new National Museum of Libya occupies the entire site, and natural history is represented in the museum’s public exhibits. Fossil specimens excavated from As Sahabi, particularly the skull and partial skeleton of Stegotetrabelodon syrticus, formed a major part of the old natural history museum’s exhibits (Figure 1). As Sahabi fossils discovered by Petrocchi are still on display today. They include a skeleton of a still unstudied fossil whale (Figure 1), a mandible of Stegotetrabelodon, and a complete skull and jaw of the unique Sahabi crocodile, Crocodylus checchiai (see article by Delfino, this volume). Table 1 lists the species new to science and generally recognised by

Table 1. New Species of Fossil Vertebrates Discovered from As Sahabi 1934-1939 Anancus petrocchii Coppens 1965 Crocodylus checchiai Maccagno 1947 “Leptobos” cyrenaicus Petrocchi 1956 Libycosaurus petrocchii Bonarelli 1947 Miotragoceros cyrenaicus Thomas 1979 Nyanzachoerus syrticus Leonardi 1954 Stegotetrabelodon syrticus Petrocchi 1941

The Second World War ended all palaeontological field research at As Sahabi for some four decades. In 1974 Noel Boaz wrote a letter to the Faculty of Science in Tripoli proposing renewed research at As Sahabi and was invited to come to Libya the following year. This visit culminated in

Figure 1. Left: The type specimen of Stegotetrabelodon syrticus on display in the old Libyan Museum of Natural History, Tripoli (Petrocchi, 1951); Right: The fossil cetacean excavated by Petrocchi in 1934, with a half-scale reproduction above, currently on display in the National Museum of Libya, Tripoli. 2

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(NFR), an international conference on the “Biotic and Climatic Effects of the Messinian Event in the CircumMediterranean” was organised by Ali ElArnauti and the staff members of the Department of Earth Sciences in Benghazi between January 14-18, 1995. The conference was held in association with the Regional Committee of the Mediterranean Neogene Stratigraphy, Montpellier (RCMNS), the International Institute for Human Evolutionary Research (IIHER), and the Research Centre, University of Garyounis, Benghazi. At the Benghazi symposium in 1995 the surviving principals of the ISRP agreed to renew investigations at As Sahabi and initiate research at Jabal Zaltan. Research was organised by Ali El-Arnauti at Jabal Zaltan in 1997 and at As Sahabi in 1998 by Europe-based teams (and members of the Department of Earth Sciences, University of Garyounis). The late Remmert Daams of the University of Madrid led a team that undertook micromammal wet-sieving at Jabal Zaltan. The results of this important work (Wessels et al., 2003), as well as from an independent field season in 1983 coorganized with Abdel Wahid Gaziry, are reported here by Wilma Willems and colleagues (this volume). Jordi Agusti, then of the Crusafont Institute of Paleontology, Sabadell and now of the Institute of Human Paleoecology, Tarragona, led a team to As Sahabi for wet-sieving for micromammals, and he reports those important results in this volume. In 2004 during the international symposium on the “Geology of East Libya” held in Benghazi, a number of papers dealing with As Sahabi research and related areas contributed as a group an important

the formation of the International Sahabi Research Project (ISRP), based at the University of Garyounis, Benghazi, and headed by Boaz, Ali El-Arnauti, and Abdel Wahid Gaziry. The project worked in the field between 1977 and 1981. The first report on the renewed research was Boaz et al. (1979) and the first geological reports were de Heinzelin et al. (1980) and ElArnauti and de Heinzelin (1985). The ISRP subsequently produced a number of scientific papers and two volumes – an earlier special issue of the Garyounis Scientific Bulletin (Boaz et al., 1982) and a multi-authored edited monograph Neogene Paleontology and Geology of Sahabi (Boaz et al., 1987). Table 2 lists the species new to science discovered and named at As Sahabi since 1979. Table 2. New Species of Fossil Abudhabia yardangi Munthe 1987 Amebelodon cyrenaicus Gaziry 1987 Cercopithecini sp. nov. Benefit et al, 2008 Dytikodorcas libycus (Lehmann and Thomas) 1987 Hexaprotodon sahabiensis Gaziry 1987

An international trade embargo and travel restrictions to Libya prevented field research from taking place for many years. In spite of this embargo and with the logistic efforts of the University of Garyounis, National Oil Corporation (NOC), the Arabian Gulf Oil Company (AGOCO), Sirt Oil Company, and the Libyan National Foundation of Research

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Figure 2. Excursion to As Sahabi during the 2004 international symposium on the “Geology of East Libya.” Above, participants at the ruins of Qasr As Sahabi; below, in exposures of the Sahabi Formation west of the Sebkhat al Qunayyin

perspective to the proceedings (Salem et al., 2008). An excursion led by Ali El-Arnauti to the As Sahabi area followed this symposium (Figure 2) and a book entitled “Short Notes and Guidebook on the Geology of Qasr As Sahabi Area” was prepared by Ali El-Arnauti and Ali ElSogher (2004) Using the opportunity afforded by this gathering, it was decided to formally organise the As Sahabi and Jabal Zaltan research into the East Libya Neogene

Research Project (ELNRP). With normalisation of international relations in 2005, renewed research was funded by the U.S. National Science Foundation and the University of Garyounis, and an initial field season was undertaken to As Sahabi in 2006 led by Noel Boaz, International Director of the ELNRP, and Ahmed Muftah and Muftah Shawaihdi, Libyan CoDirectors of the ELNRP (Figure 3). Following up on this beginning a palaeontological field team led by Paris

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volume. In April, 2007 systematic drilling in the Sahabi Formation, under the direction of Noel Boaz, Ahmed Muftah, and Muftah Shawaihdi, for the purpose of ascertaining lateral facies variation to the west of the main exposures was undertaken (Figure 5), along with limited palaeontological survey. Ahmed Muftah and colleagues report on the important stratigraphic conclusions of this research in this volume. Muftah’s analysis has convincingly refined the age of Formation M to the Late Miocene. The

Figure 3. ELNRP field team at As Sahabi, September 19, 2006. The field teams in 2006 and 2007 carried the flag of the Explorers Club, New York. L-R: Fathi Salloum, Ahmed Muftah, Mohammed Al-Faitouri, Noel Boaz, Muftah Shawaidhi. Kneeling; Driver. palaeontological field team led by Paris Pavlakis, and geological team led by Ahmed Muftah and Muftah Shawaihdi, worked at As Sahabi during February and March, 2007 (Figure 4). Significant new vertebrate fossils were recovered during this and the subsequent field season in April, 2007, and most of these specimens have been included in the discussions of their relevant taxonomic groups in this

Figure 5. Drilling Boreholes 1 and 2 at As Sahabi, April, 2007 absence of a thick gypsiferous “Formation P” in the west, at the site of the boreholes, is evidence for a more localised extent of this deposit. This is one of the first instances in which terrestrial boreholes have been drilled to elucidate stratigraphy in vertebrate palaeontological research. In June, 2007 a short geological field season was carried out by Claus Beyer of CB-Magneto, Stavanger, Norway, in association with Ahmed Muftah and Muftah Shawaihdi. Initial palaeomagnetic results from the Sahabi Formation are reported by Beyer in this volume. Beyer discovered the long-sought-for occurrence of potassium-rich glauconites at As Sahabi,

Figure 4. ELNRP Field Crew, FebruaryMarch, 2007

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Miotragoceros cyrenaicus from U-1 has more primitive attributes than the type skull of this species described from western localities at As Sahabi by Petrocchi in 1952. H.B.S. Cooke in the 1980’s made similar observations based on the suid fauna from As Sahabi. All these studies suggest a time interval of perhaps 1 ma or more between Members U and V of the Sahabi Formation, but a definitive conclusion on this point must await further detailed stratigraphic and geochronological work.

which have yielded the first potassiumargon dates (7.5 to 7.7 ma from Formation M). The age of the bulk of the palaeontologically important Sahabi Formation collections was revised by Boaz et al. (2008) to the Late Miocene, but unambiguous geological support for this conclusion is still pending. More data are needed. Further geochronological work on a putative ash level in U-1, as well as potassium-rich glauconites, is needed in order to bring radiometric dates to bear on this problem. Two vertebrate palaeontological studies in the current volume bring up the issue of the time interval covered by the Sahabi Formation faunal collections. From surface outcrop stratigraphy of the localities of discovery, levels from which fossil vertebrates derive are assessed to be primarily Member U (units U-1 and U-2), but Members T and V, both above and below Member U, are considered also to have yielded fossils (see Muftah et al., this volume). Sanders’ paper on previously undescribed As Sahabi proboscideans in the Tripoli museum collected in the 1930’s notes a significant taxonomic difference between these specimens, all anancines, and the assemblage from As Sahabi originally reported by Gaziry in the 1980’s. The former specimens were all collected in localities in the western area of exposure of the Sahabi Formation, from sediments of upper Member U or Member V, whereas virtually all of the fossils collected since the 1970’s derive primarily from unit U-1 exposed in eastern localities near the Sebhkat al Qunayyin. Gentry (this volume) notes that a new partial skull of the bovid

IDENTIFICATION AND RECORDING OF LOCALITIES All fossil localities established by the ISRP at As Sahabi were recorded on aerial photographs and mapped stratigraphically (see de Heinzelin and ElArnauti, 1987). The same system of naming and recording localities has been followed by the ELNRP. As part of renewed fieldwork all P localities were relocated and recorded by GPS positioning. In 2007 all 62 Petrocchi localities (Figure 6) were precisely re-located, surveyed, and recorded by GPS position. CURRENT STATUS OF THE COLLECTIONS Collections made at As Sahabi by Italian teams under the direction of Carlo Petrocchi in the 1930’s (see Rook, this volume) are in several venues in Italy and in the National Museum of Libya in Tripoli. Most or all of the specimens in Italy have been described. The As Sahabi specimens in Tripoli include the type specimen of

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Stegotetrabelodon syrticus (Figure 7) and a number of previously undescribed proboscideans (Sanders, this volume), hippopotamids (Pavlakis, this volume), and anthracotheres (Pavlakis and Boaz, this volume).

By agreement, all fossil collections from As Sahabi and Jabal Zaltan that have been collected by the teams of the ELNRP and its predecessor, the International Sahabi Research Project, will be permanently housed at the Earth Sciences Museum of the University of Garyounis, Benghazi (Figure 8). As newly discovered specimens are studied and described in the various laboratories of ELNRP scientists around the world, their whereabouts are recorded in the digitised specimen catalogue. These databases are maintained at the International Institute for Human Evolutionary Research in Oregon, U.S.A., and at the University of Garyounis, Benghazi, Libya. CONTINUING RESEARCH AND MUSEOLOGICAL DEVELOPMENT As impressive as are the past palaeontological discoveries at As Sahabi, the future will see an increase in numbers and quality of specimens. Increasing the collection is necessitated by a less-than-full knowledge of the morphology of taxa already documented and ignorance of the full diversity of the past fauna. All surface outcrops and all established â&#x20AC;&#x153;Pâ&#x20AC;? fossil localities accessible in the As Sahabi area have now been intensively surveyed at least twice since the inception of research in 2006. All early fossil localities established by the Petrocchi teams have also been surveyed at least twice. The rate of recovery of significant discoveries from surface survey alone has slowed because the rate of

Figure 6. As Sahabi fossil localities (Petrocchi, 1951)

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Figure 7. Left: Initial preparation work on the fossil proboscidean fossils from As Sahabi collected by the Petrocchi expeditions in the 1930â&#x20AC;&#x2122;s and now housed in the Libyan National Museum, Tripoli. The type specimen of Stegotetrabelodon syrticus Petrocchi 1941, in dire need of restoration, is in the background. Right: A 1996 Libyan postage stamp commemorating the famous discovery.

Figure 8. Left: The main gallery of the Earth Science Museum at the University of Garyounis. New exhibit cases and cabinets have fossils and geological specimens from As Sahabi on display with temporary labelling, but permanent exhibits have yet to be developed. Right: The preparation laboratory of the Earth Science Museum of the University of Garyounis in September, 2006, illustrating the many unpacked boxes of fossils from As Sahabi relocated from the former ISRP lab at the Garyounis Research Centre. These fossils have now been placed in museum trays and stored in new collection storage cabinets in the museum. Specimens are in need of professional preparation, casting, and curation. 8

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accessible for comparative study by researchers will increase. Concomitant with increasing collections will be the demand for public dissemination of news and interpretations of the discoveries. Both are central parts of the mission of museums. The ELNRP’s agreement with Shell Libya (Figure 9) includes these important components of museological development for Libya.

aeolian erosion at As Sahabi is not rapid enough to uncover new fossiliferous exposures from one field season to the next. “Sweeping” of the Recent overlying coarse sand in potentially fossiliferous areas has not yielded good results at As Sahabi, perhaps because the winds are not as strong here as at other North African fossil sites, such as the Fayum, Egypt, and Toros Menalla, Chad, where this technique has been successful. Excavation for macrofaunal remains in the easily excavated unconsolidated sands of Member U of the Sahabi Formation, however, holds great promise and there are dozens of square km of accessible and known fossiliferous sediments. Wet-sieving for micromammal remains at productive localities will also intensify at As Sahabi in the coming years of work. Palaeontological surface survey, wet-sieving, and excavation in the extensive fossiliferous exposures of Jabal Zaltan will add further to the numbers of specimens coming into the collections. As fieldwork continues, the need for the development of museum resources to adequately store collections and make them

UNIVERSITY AND ELNRP COLLABORATION As research proceeds, many specialty studies within the broad disciplines of geology and palaeobiology will need to be added to the repertoire of the East Libya Neogene Research Project. The need to more intensively investigate the age and dating of the sediments will bring in specialists in geochronology. The need to understand and better model ancient sedimentary environments will require new specialists in sedimentology and geochemistry. Gaining a better knowledge of past floras, through both pollen and fossil

Figure 9. An agreement with Shell Exploration and Production Libya (General Manager Marc Gerrits, in center) will allow the ELNRP (Noel Boaz, International Director, at left) and Libyan museums (Giuma Anag, Chairman, Department of Archaeology, National Museum of Libya, at right) to work together in developing museum collections and exhibits.

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research missions. One such research and training agreement that grew out of respective faculty membersâ&#x20AC;&#x2122; involvement in the ELNRP was signed in Benghazi on March 5, 2008 between the University of Garyounis and the University of Athens (Figure 10). We look forward to the further development of such important and mutually beneficial international interuniversity collaborations. It is only through wide academic and institutional networks that we will be able to adequately address the daunting but exciting research and training challenges posed by the wealth of discovery now being presented to us from the Neogene of Libya.

wood, is key to a better grasp of Late Neogene palaeoenvironments. As more and more previously unknown vertebrate and invertebrate taxa are discovered, more specialists on these groups will come into the project. No single university or research institute is large or diverse enough to encompass all the requisite specialties or training opportunities now needed in a large interdisciplinary research project like the ELNRP. Consequently, collaborative arrangements with universities and other research organisations are essential. These agreements can serve to train graduate students, provide valuable opportunities for faculty research, and advance universitiesâ&#x20AC;&#x2122;

Figure 10. Signing ceremony between University of Garyounis and University of Athens for collaborative research and academic programs, Benghazi, March, 2008. Left to right: A. Shukri, I. Velissaropoulou, University of Athens Vice-Rector I.K. Karakostas, M. El-Mansoury, University of Garyounis Vice-President M. El-Awami, H. El-Braasi, N. Boaz, E. Pavlakis, P. Pavlakis, A. El-Hawat, A. El-Arnauti, B. Mohammed, F. Salloum.

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REFERENCES BOAZ, N.T., GAZIRY, A.W. and ELARNAUTI, A. (1979). New fossil finds from the Libyan Upper Neogene site of Sahabi. Nature 280, 137-140.

EL-ARNAUTI, A. and DE HEINZELIN, J. (1985). Le Néogène en Libye. Paléobiologie Continentale, Montpellier 14, 269-282.

BOAZ, N.T., GAZIRY, A.W., DE HEINZELIN, J. and EL-ARNAUTI, A. (1982). Results from the International Sahabi Research Project (Geology and Paleontology). Garyounis Scientific Bulletin, Special Issue 4. 144 p.

EL-ARNAUTI, A. and EL-SOGHER, A. (2004). Short Notes and Guidebook on the Geology of the Qasr As Sahabi Area. Tripoli, Earth Science Society of Libya, 95 p. PETROCCHI C. (1951). Notizie generali sul giacimento fossilifero di Sahabi. Storia degli scavi. Rend. Accademia Nazionale dei Quaranta 3, 8-31.

BOAZ, N.T., EL-ARNAUTI, A., GAZIRY, A. W., DE HEINZELIN, J. and BOAZ, D. D. (eds) (1987). Neogene Paleontology and Geology of Sahabi. Alan. R. Liss, New York, 401 p.

SALEM, M.J., EL-ARNAUTI, A. and A. ELSOGHER SALEH (eds) (2008). The Geology of East Libya, vol. III. Sedimentary Basins of Libya. Tripoli, Earth Science Society of Libya.

BOAZ, N.T., EL-ARNAUTI, A., AGUSTI, A., BERNOR, R.L., PAVLAKIS, P. and ROOK, L. (2008). Temporal, lithostratigraphic, and biochronologic setting of the Sahabi Formation, North-Central Libya. In: The Geology of East Libya, vol. III. Sedimentary Basins of Libya (eds M.J. Salem, A. ElArnauti and A. El-Sogher Saleh). Earth Science Society of Libya, Tripoli.

WESSELS, W., FEJFAR, O., PELÁEZCAMPOMANES, P., MEULEN, A. VAN DER and DE BRUIJN, H. (2003). Miocene small mammals from Jebel Zelten, Libya. In: Coloquios de Paleontología. En Honor al Dr. Remmert Daams (eds N. LópezMartínez, P. Peláez-Campomanes and M. Hernández Fernández). Coloquios de Paleontología, Volumen Extraordinario 1, 699-715.

DE HEINZELIN, GAZIRY, A.W.

J., EL-ARNAUTI, and (1980). A preliminary revision of the Sahabi Formation. In: The Geology of Libya (eds M.J. Salem and M.T. Busrewil). Academic, New York, 1, 127133.

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The Discovery of the As Sahabi Site: Ardito Desio or Carlo Petrocchi? LORENZO ROOK

ABSTRACT It is widely known that two Italian researchers in the 1920's and 1930's contributed extensively to the geology and palaeontology of the celebrated Late Neogene vertebrate-bearing sediments of As Sahabi (Libya), Ardito Desio and Carlo Petrocchi. Ardito Desio was surely the most famous Italian geologist of the past century. He explored and surveyed large parts of the Libyan Sahara, during the 1920's and 1930's providing data and maps still of use today. Carlo Petrocchi was the palaeontologist who most contributed to the recovery and study of the vertebrate remains from As Sahabi. He published several papers on the site and fauna (notably the As Sahabi proboscideans, including naming the species Stegotetrabelodon syrticus). Ardito Desio published in 1950 a popular book titled “Le Vie della Sete” (“Thirsty Paths”) describing his adventures and discoveries during his Saharan explorations. Desio here claimed he first discovered the occurrence of large fossil mammals at As Sahabi and also published a picture of the site. A few months later Petrocchi published an open letter to Desio defending his own role in the recognition of the importance of the As Sahabi site. An open public debate between the two followed. A careful reading of these documents can help us in assessing who first discovered the As Sahabi site, as well as Petrocchi’s subsequent difficulties in obtaining an academic position in Italy. These documents also elucidate some aspects of the early history of palaeontological work at As Sahabi, and are useful in correlating early fossil localities with discoveries made during our latest surveys in the area.

Lorenzo Rook, Earth Sciences Department, University of Florence, Via G. La Pira, 4 – 50121 Firenze, Italy, lorenzo.rook@unifi.it

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years 1931 and 1932. During these short stays at As Sahabi, Desio discovered more fossil remains and collected some small samples of fossil vertebrates. These fossils were transferred to Italy and housed in the “Museo Civico di Storia Naturale” in Milan and studied by Desio himself (molluscs) and by other emi n ent I t ali a n palaeontologists. Fossil vertebrates were studied by Prof. C. Airaghi (Milan) and by Prof. D’Erasmo (Naples). In various geological reports (1931, 1933) Desio mentions the occurrence of “fossil bones” without any further detail. The first report of the study of the fossil vertebrates collected as geological samples by Desio was given by D’Erasmo in 1933 and 1934. The taxonomic determinations by D’Erasmo (1933) are far from informative. The terrestrial vertebrates are identified only as a few reptiles and as undeterminable ungulate mammals. Nothing more was forthcoming in the 1934 paper, where the mammal postcranial bones were ascribed to cervids, antelopes or gazelles, and possibly equids. Another Italian geologist passed by As Sahabi in these early years. A geologist from the University of Pisa, G. Stefanini, visited the area in 1933 and reported the occurrence of abundant marine and terrestrial fossils (Stefanini, 1934a) again without any taxonomic determination of the fossil vertebrates identified.

EARLY SURVEYS AT QASR AS SAHABI The celebrated Late Neogene vertebrate-bearing sediments of As Sahabi (Libya) have been an object of detailed geological and palaeontological fieldwork and research by the International Sahabi Research Project from the late 1970's to 80's, coordinated by N. Boaz, Ali ElArnauti, and the late Wahid Gaziry (Boaz et al., 1987). In fact, the occurrence of fossil bones in the neighbourhood of an Italian fort at Qasr As Sahabi was first noted by Italian soldiers stationing at the fort in the early 1930s. As Sahabi is located about 130 km south of Ajdabiya, along the road going south into the Libyan Sahara to Jalu [Gialo] and Al Kufra. There was at As Sahabi in the 1920’s and 1930’s an active, small Italian army station with an airfield for small airplanes. Being on the road to various sites into the Libyan desert, As Sahabi was always crossed by caravans and explorers. An Italian army convoy heading southward to Jalu passed through As Sahabi and stopped there on November 26, 1930. A geologist, Ardito Desio, was travelling together with the Italian soldiers. Desio was probably the most famous Italian geologist and explorer of the past century. He noted the occurrence of marine fossils in the surroundings of the fort (Desio, 1931). Desio was engaged during this time in very intense survey activity, especially focused on geological survey and mapping. He was a pioneer in Libyan geology. Going back and forth from Benghazi to various target areas within the Sahara Desert he passed and stopped at As Sahabi in the

PETROCCHI’S CONTRIBUTION TO THE SAHABI FOSSILIFEROUS SITE Curious Italian soldiers and other Italian personnel assigned to remain at the

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for the preparation of the collected material. Continuing his work at As Sahabi was not easy. After the initial enthusiasm, Petrocchi was left without substantial support. No geologist or palaeontologist was designated to collaborate with him. The activity of these years resulted in the assembling of a large fossil collection (made up by some thousand fossils), that were stored in Benghazi and later (in 1939) transferred to Libyan Museum of Natural History in Tripoli. In 1939 Petrocchi was named director of the Libyan Museum of Natural History. He was forced to leave Benghazi and move to Tripoli. At the beginning of 1940, Petrocchi was asked to prepare a palaeontological exhibition for an international exhibition in Naples (“Mostra Triennale d’Oltremare”). The beginning of the Italian participation in the Second World War made it impossible for Petrocchi to come back to Tripoli and, although he asked permission to go back to Tripoli with his family, he was obliged to remain in Italy. In the following years, working at the Institute of Palaeontology of the University of Rome, he was able to continue working on the As Sahabi material that was “temporarily” transferred in Italy (Petrocchi, 1951d,e, 1954, 1956). Some taxa were studied by Italian palaeontologists. Crocodiles were studied by Maccagno (1948, 1954) and suids by Leonardi (1952). The new anthracotheriid from As Sahabi, Libycosaurus petrocchii, was originally described by Bonarelli (1947) in honour of Petrocchi, but as a dinosaur. The wish of Petrocchi to publish a

As Sahabi fort used to excavate the fossil remains that were so common in the surroundings of the military installations. In early 1934, a team of sanitary personnel realised the possible scientific importance of these common findings and reported the fact to the local authorities (the Governor of the Cyrenaica Region). Following these reports, Dr. Carlo Petrocchi was charged to study these fossil remains and to survey the As Sahabi area. During his first survey, Petrocchi identified one of the most significant fossils from As Sahabi, the complete skull of a proboscidean. After about one month of delicate and heavy work, Petrocchi was able to complete the recovery of the specimen and to transport it to Benghazi. The authorities were much interested in the recovery of this spectacular fossil (which Petrocchi later named as the new genus and new species Stegotetrabelodon syrticus) and in the abundance of fossils from the As Sahabi area. The governor of Cyrenaica invited Prof. G. Stefanini, who had already shortly visited the site one year before, to survey the site together with Petrocchi in order to provide a report on the importance of the fossiliferous site. The survey was successful and Stefanini and Petrocchi agreed to announce the discovery in two contemporary publications (Petrocchi 1934, 1936; Stefanini 1934b). Supported by the scientific opinion of G. Stefanini, the colonial authorities confirmed to Petrocchi the charge of continuing survey and excavation of fossils at As Sahabi. For six years (from 1934 to 1939) Petrocchi conducted several seasons of field survey and excavation, and intense laboratory work

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monograph volume on the As Sahabi mammal fauna was not realised, despite the fact that he published such a volume edited by a historical Italian institution, the “Accademia Nazionale delle Scienze detta dei Quaranta.” Accurate reports of field activities (not easy given the harsh conditions and the technical difficulties in those early years), the history of the findings and recovery, as well as the analytic study of part of the collected mammals, have been published by Petrocchi in a number of papers (Petrocchi 1934a, 1936, 1941, 1942, 1943a,b, 1951c,d,e, 1954, and 1956). Some of these are a source of precious information on several aspects of the early history of the palaeontological work at As Sahabi, and correlate this early information with discoveries made during surveys in the area conducted some 70 years later (see Boaz et al., this volume). The writer had in fact the occasion to visit the As Sahabi area during an excursion organised within the conference “Sedimentary Basins of Libya, Third Symposium, Geology of East Libya” held in Benghazi (Libya) in November, 2004. During the short trip we visited the ruins of the Italian fort and, on the basis of Petrocchi’s descriptions and the field experience of Noel Boaz and Ali ElArnauti, we located the site of discovery of the famous Stegotetrabelodon skull. The site was described by Petrocchi to be located some hundred metres north of the “Campo di aviazione.” Here we discovered some removed sediment, bone fragments, and many green fragments of bottle glass. Almost fully lying within the desert sand, a bottle was discovered to be intact and it was

Figure 1. Label of the bottle found at the Stegotetrabelodon site (P19) during the 2004 survey. still bearing a partially eroded label (Figure 1). The label, although damaged still bears the indication: [...]maceutica coloniale [...]ato di sodio [...]Italia - Bengasi and it is enough to understand the following information: the first line indicates the producer, i.e. the pharmaceutical institute of the Italian Colony, that was located in Benghazi, as indicated in the third line of the label. The middle line indicates the content, i.e. some sodium salt. It was exciting to find an item left in the desert for about 70 years. And it has been even more exciting to find in one of the papers by Petrocchi (1943a) the evidence that this was a chemical used during the field preparation as a hardening agent for the fragile fossil bones (Figure 2). In this publication

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geological explorations. Desio claimed there that he first discovered the fossiliferous site of As Sahabi during the 1931 Libyan trip, and that he noted there the occurrence of a number of fossil mammals in the surrounding of the As Sahabi fort. In this book Desio described (p. 73) what he saw that morning at As Sahabi and refers to a number of well-identified animals (crocodiles, four-tusked mastodonts, anthracotheres, rhinoceroses, and antelopes), despite that he had always maintained in the scientific literature that the bones from As Sahabi were too fragmentary for any taxonomic determinations (Desio 1931, 1933). In the same 1950 book (p. 189) Desio published a picture of a proboscidean pelvis from As Sahabi still under restoration and referred to it as being prepared in the laboratory of the Natural History Museum in Tripoli (Figure 3). On the same pages (pp. 189-190) he again claims to have discovered the important palaeontological site. A few months later (April 26, 1951) Petrocchi (1951a) published an open letter to Desio defending his own role in the recognition of the importance of the As Sahabi site and disputing the unauthorised publication (and incorrect caption) of the picture on page 189 of Desio’s book. The picture, by Petrocchi, illustrates fossils excavated at As Sahabi by Petrocchi in 1938 under restoration in the Benghazi laboratory . In order to defend himself and his scientific role in bringing to light knowledge of As Sahabi during six years of hard work in the Libyan desert and in the Benghazi laboratory, Petrocchi (1951a) summarised the history of the exploration

Petrocchi in fact describes (on pages 32 and 33) how they preserved the bone using sodium silicate (“silicato di sodio”).

THE 1950’s DEBATE In 1951 a very harsh public debate, carried out through the publication of open letters, was conducted by C. Petrocchi (1951a, 1951b) versus A. Desio (1951). Although these papers are not a scientific contribution to our knowledge of the As Sahabi site and fauna, a careful reading of these documents can help in understanding some aspects of the Italian research in these years as well as to guess some of the personal relationships between an established professor in the Italian academy and a “simple” researcher that never achieved an academic position. Ardito Desio published in August, 1950 a popular book entitled “Le Vie della Sete” (“Thirsty Paths”) describing his travels and discoveries during his Libyan

Figure 2. Early excavation at the Stegotetrabelodon site (P19). The picture is from Petrocchi (1943a). Note the person on the right holding a bottle of hardener.

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refers to Petrocchi not as a scientist (“professore di lettere”) but nothing more than a technician able just to collect fossil bones. The conclusion of Desio’s (1951) reply is to be noted “…too much time has been wasted already on the subject and I will never be back on such a discussion.” In fact no other mention of As Sahabi is present in Desio’s subsequent bibliographic production (cf. Desio, 1987). One month later Petrocchi (1951b) wrote another letter to Desio. The document reveals the sad mood of a scientist whose work had always been undervalued because of prejudice and personal low esteem from one who, in a powerful position, was not able to act and judge with the necessary objectivity and correctness. The personal misunderstanding and conflicts between Desio and Petrocchi must have been of long duration, since at least the late 1930’s.

of As Sahabi and the role of the scientific and administrative authorities. He included Desio, first as field geologist and later as scientific head of the Libyan Museum of Natural History during the six years of his work at the site. Desio replied to Petrocchi (1951a) on July 15, 1951 (Desio 1951). The way this letter is written is surprising. It is very harsh and somewhat arrogant, indicating an unpleasant attitude towards somebody Desio had a very low opinion of. First of all, apologising for his delay in publishing his reply, Desio states that in the preceding months he was a member of a national commission for selecting a professorship in palaeontology in which Petrocchi was one of the applicants. Desio does not mention the result of the selection but lets it be understood how his negative opinion of Petrocchi was crucial in the selection. Desio

Figure 3. Picture published by Desio (1950:189). Petrocchi (1951a) disputed Desio’s unauthorised publication and the incorrect caption provided by Desio. 18

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I tried to have information through the association that is in charge of the Desio archive (www.arditodesio.it), but my emails to info@arditodesio.com on January 24, 2007 and February 13, 2007 remained without answer. As a matter of fact, none of the As Sahabi mammal remains collected by A. Desio are currently stored in the Milan Museum of Natural History (Dr. Cristiano Dal Sasso, pers. comm.) or in Naples. There, the Palaeontological Museum of the University preserves the collections studied by Prof. D’Erasmo and there is a large collection from As Sahabi (possibly sent to him by Desio), but no mammal is recorded. There are only shark teeth in this collection (Dr. Maria Del Re, pers. comm.). From published and archival evidences it is clear that Desio first passed though As Sahabi, but he underestimated or even did not understand the importance of the site. After the richness and real value of the site had been put in evidence by the hard work of Petrocchi, Desio was not able to resist the temptation to attribute to himself the merit of the discovery of the site, only because he had had the opportunity to stop there a few years before. Petrocchi spent six years working in extremely difficult conditions to recover the As Sahabi mammal fauna. The celebrated geologist Ardito Desio did not understand the richness or the value of what Petrocchi was working with.

CONCLUSIONS The public debate between Petrocchi and Desio apparently concerned whom was to be ascribed the discovery of the As Sahabi site, but it was probably the expression of older and deeper bad relationships between the two scientists. Desio has been an extremely successful geologist and explorer. The attempt to attribute to himself the discovery of the As Sahabi vertebrate site did nothing to add to his career or personal prestige. What is clear from the available documents is that Desio was the first geologist to stop at As Sahabi (November, 1931) and to sample fossils from the area. However, he provided no evidence in his scientific production prior to 1934 (when Petrocchi announced the discovery of the Stegotetrabelodon skull) that he realised the importance of the site. In fact it is only in 1935 (after Petrocchi and Stefanini published the new remains discovered and the potential extent of the As Sahabi vertebrate assemblage) that Desio (1935a) refers to As Sahabi, saying that the site became renamed after the discovery of proboscidean remains. Before Petrocchi’s field activity very little evidence was available from As Sahabi. Palaeontologists working with Desio were not able to identify any taxon from the few fragments Desio collected (Desio 1951:3). Desio confirms that he collected a number of mammal remains and that these were stored in the Milan “Museo Civico di Storia Naturale” and that most of them were sent for study to Prof. D’Erasmo in Naples, who, Desio says, studied and identified the specimens. Desio refers to a list of specimens (1951:4) but he does not offer any proof of the real consistency of this list.

REFERENCES BOAZ, N.T., EL-ARNAUTI, A., GAZIRY, A.W., DE HEINZELIN, J. AND DECHANT BOAZ, D. (1987). Neogene Paleontology and Geology of Sahabi. Alan R. Liss, New York, 401p.

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LEONARDI, P. (1952). Resti fossili di Sivachoerus del giacimento di Sahabi in Cirenaica (Africa settentrionale). Atti Acc. Naz. Lincei, Rend., 8, 166-169.

BONARELLI, G. (1947). Dinosauro fossile del Sahara Cirenaico. Riv. Biol. Colon. 8, 23-33. D’ERASMO, G. (1933). Sui resti di vertebrati terziari raccolti nella Sirtica dalla Missione della Reale Accademia d’Italia (1931). Atti R. Accad. Lincei, ser. 6, 18, 656-658.

MACCAGNO, A. (1948). Descrizione di una nuova specie di Crocodilus del giacimento di Sahabi (Sirtica). Mem. Atti Acc. Naz. Lincei, ser. 8, 1(4), 63-96.

D’ERASMO, G. (1934). Su alcuni avanzi di vertebrati terziari della Sirtica. In: Missione Scientifica della Regia Accademia d’Italia a Cufra (1931) (ed A. Desio), Roma, 3.

MACCAGNO, A. (1954). I coccodrilli di Sahabi. Rend. Accademia Nazionale dei Quaranta 4/5,77-117. PETROCCHI, C. (1934). I ritrovamenti faunistici di es-Sahabi. Rivista delle Colonie Italiane, 7, 733-742.

DESIO, A. (1931). Osservazioni geologiche e geografiche compiute durante un viaggio nella Sirtica. Boll. R. Soc. Geogr. Ital., ser. 6, 8, 275-299.

PETROCCHI, C. (1936). Relazione sui ritrovamenti di es-Sahabi. Atti del secondo Congresso di Studi Coloniali (Naples, 1934) 3, 238-246.

DESIO, A. (1933). Nuovi dati sulla geologia della Libia. Mem. Geol. Geogr. Giotto Dainelli 3, 205-225.

PETROCCHI, C. (1941). Il giacimento fossilifero di Sahabi. Boll. Soc. Geol. Ital., 40(1), 107-114.

DESIO, A. (1935a). Appunti geologici sui dintorni di Sahabi (Sirtica). Rend. R. Ist. Lomb. Sci. Lett., ser. 2, 68, 137-144.

PETROCCHI, C. (1942). Sahabi: una nuova pagina nella storia della Terra. Annali dell’Africa Italiana 5(3), 745-751.

DESIO, A. (1935b). Missione Scientifica della Regia Accademia d’Italia a Cufra (1931). 1, Roma, 465 p.

PETROCCHI, C. (1943a). Il giacimento fossilifero di Sahabi. Collezione scientifica e documentaria del Ministero dell’Africa Italiana, Verbania, 162 p.

DESIO, A. (1950). Le Vie della Sete. Hoepli, Milano, 336 p. DESIO, A. (1951). A proposito del giacimento fossilifero di Sahabi. Milano (July 15, 1951), 8 p.

PETROCCHI, C. (1943b). Sahabi: Eine neue seite in der Geschichte der Erde. Neues Jahrbuch Min. geol. Paläont., Monatshefte, 1943(B): 1-9.

DESIO, A. (1987). Sulle vie della sete, dei ghiacci e dell’oro. De Agostini, Milano.

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orientale. Boll. Geogr. del Governo della Tripolitana e Cirenaica 5/6, 152-157.

PETROCCHI, C. (1951a). Il giacimento fossilifero di Es-Sahabi. Roma (April 10, 1951), 31 p. PETROCCHI, C. (1951b). Ancora a proposito del giacimento fossilifero di Es-Sahabi. Roma (August 10, 1951), 8 p. PETROCCHI, C. (1951c). Nota sulla fauna terziaria di Sahabi. Atti del 42o Congresso della SocietĂ Italiana per il Progresso delle Scienze (Tivoli, 1949), 479-481. PETROCCHI, C. (1951d). Nota preliminare allo studio di alcuni resti fossili del giacimento di es-Sahabi, riferibili a Proboscidati e a Bovidi. Applicazione di un nuovo procedimento biometrico alla paleontologia sistematica. Istituto di Geologia e Paleontologia UniversitĂ di Roma, 16 p. PETROCCHI C. (1951e). Notizie generali sul giacimento fossilifero di Sahabi. Storia degli scavi. Rend. Accademia Nazionale dei Quaranta 3, 8-31. PETROCCHI, C. (1954). I Proboscidati di Sahabi. Rend. Accademia Nazionale dei Quaranta, 4/5,1-76. PETROCCHI, C. (1956). I Leptobos di Sahabi. Boll. Soc. Geol. Ital. 75, 1-36. STEFANINI, G. (1934a). Giacimento miocenico a vertebrati nella Sirtica. Atti Soc. Tosc. Sci. Nat., Processi Verbali (March 12, 1934), 43(2), 27-28. STEFANINI, G. (1934b). Sulla scoperta di resi fossili di vertebrati nella Sirtica

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Special Issue, No. 5

The Pre-Messinian Miocene Stratigraphy and Sedimentation in the Marada-Zaltan Area, Central Sirt Basin, Libya

AHMED S. EL HAWAT

ABSTRACT The Middle Miocene Marada Formation is a second-order stratigraphic sequence bound by well-defined unconformable boundaries. It forms a terminal phase in the post-rift megasequence infilling the Sirt Basin, and consists of vertically arranged lowstand (LST), transgressive (TST) and highstand (HST) systems tracts. These constitute six vertically stacked carbonateâ&#x20AC;&#x201C;siliciclastic genetic depositional units exhibiting lateral facies changes of the carbonate-dominated Marada area to siliciclastics in Jabal Zaltan to the south. The LST consists of fluviatile and fluviomarine deposits rich in vertebrate fauna and flora. These pass laterally northwards into estuarine calcareous sandstone facies infilling a channel system forming the base of the section. To the south, the start of the TST is marked by deposition of thick lagoonal shales over the fluvio-estuarine deposits. These change northward into cross-bedded bioclastic carbonate barrier bars and sandy bioclastic tidal inlets and a delta complex that transgress over the lagoonal shales. Together, these are stacked in repeated transgressive-regressive architecture in response to cyclic influx and cessation of siliciclastic supply and created accommodation space. During maximum flooding carbonate sedimentation extended into the siliciclastic-dominated south and developed a condensed section (CS) to the north. It is characterised by lithification, build-up of oyster banks, and development of a regionally extended Echinolampas marker. The following HST consists of open marine wackestone banks alternating with prograding deltaic marl and calcareous sandstone shoestring facies. Ultimately, the sequence stratigraphic architecture of the Marada Formation and the alternation of carbonate and siliciclastic cyclic sedimentation are attributed primarily to the interplay of steady eustatic sea-level change and overprinting by spasmodic tectonic activity of the Sirt rift complex during the Middle Miocene.

Ahmed S. El Hawat, Department of Earth Sciences, Garyounis University, Benghazi, Libya, ashawat@ltt.net

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INTRODUCTION

and White 1965; see also Wessels, et al. and Sanders, this volume). Comparing this fauna to that of East Africa, Pickford (1991) estimated that it is Langhian in age at about 16.5 ma. The occurrence of foraminifera Borelis melo and Borelis melo curdica in the carbonate facies also suggest Middle Miocene age. Meanwhile, fauna and flora indicate that tropical and savanna climatic conditions prevailed during the Middle Miocene in Libya (Principi, 1932; Desio, 1935; Savage and Hamilton, 1973; Pickford, 1991).

The mixed carbonateâ&#x20AC;&#x201C;siliciclastic succession of the Marada Formation is exposed around the Marada Oasis area in central Sirt basin (Figure 1) where the carbonate-dominated succession of Dur Marada and Dur Zaqqut to the north changes southwards to siliciclastic domination in Jabal Zaltan. The mammalian faunas found in the sands of Jabal Zaltan are considered to be of Early Burdigalian age (Savage and Hamilton, 1973; Savage

Figure 1. Location map of the Marada â&#x20AC;&#x201C; Jabal Zaltan area showing the location of the measured sections and the line of the stratigraphic cross-section running parallel to the depositional slope in a north-south direction. The map also shows different geographic locations and major oil fields that take a trend parallel to the axis of subsurface structures.

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Tidal Flat Facies This facies association consists of tidal flat, tidal channel infill and marsh facies. These are exposed to the north and above the fluvial deposits in Jabal Zaltan where they are closely associated with the estuarine channels. Tidal flat sediments consists of 50 cm to 3 metres thick units of mudstones and sandy mudstones, interlaminated sands and shales that are arranged in fining-up and coarsening-up cycles. The sand is light gray and yellowish brown in colour, medium to fine-grained, friable, planar and micro-cross laminated. The shale and silt are dark gray and green, and wavy laminated. Sedimentary structures include flaser and lenticular bedding, with wavy and ripple lamination. Bioturbation includes Diplocraterion, Ophiomorpha, Thalassinoides, Caegichnus, Aestites and Corophoides burrows. The marsh facies on the other hand are 1-2 m thick, dark gray and ochre brown mudstone, siltstone and sandy mudstone showing massive or irregular lamination, flat mud clasts of rippled desiccation cracks and lignite rootlets. It shows rare bioturbation but Hydrobia and plant leaf impressions are common. Channels of the tidal flat association form flat-topped lenses 3 m deep and up to 15 m wide. These exhibit an erosional base and contain lag of wood and bone fragments, animal teeth, oyster shells, and crustacean fragments. Their infill is fining-up and consists of point bars arranged in low-angle unilateral beds. Channel troughs are filled by troughand-ripple laminated sandstone, calcareous sandstone, and alternating sands and mudstones.

Depositional Facies The sedimentology of the Marada sequence was studied extensively by El Hawat (1980) and Selley (1969). Nine vertically stacked and laterally changing facies are recognised and their geometry, vertical and lateral distribution is illustrated the cross section (Figure 2). These are 1. fluvial (siliciclastic); 2. tidal flat (siliciclastic); 3. estuarine (mixed); 4. lagoonal (mixed); 5. barrier bar (carbonate); 6. tidal deltas and inlets, (mixed); 7. intertidal (carbonate); 8. marine banks (carbonate); and 9. marine deltas (mixed). Fluvial Facies The fluvial facies consists of crossbedded, friable yellowish orange to brown and green sand, silt and shale. These are arranged in up to 6 m thick, fining-up channel infill cycles with basal lag of reworked clay clasts, bones and silicified wood fragments. The sand is ill-sorted, coarse to medium quartz arenite. The shale and silt are yellowish to greenish colour with lignite rootlets and calcareous nodules that suggest soil formation. Palaeocurrent indicators suggest a unimodal northern flow direction, however the top of the upper cycles in the section show some reverse flow and calcite cementation that may suggest early river mouth drowning and estuarine influence. Associated fossils include silicified tree trunks and a rich collection of vertebrate fauna of elephants, rhinoceroses, pigs, giraffe, hippopotamus, birds, crocodiles, turtles and hyenas (Savage and White, 1965; Savage and Hamilton, 1973; Pickford, 1991).

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channel infill cycles. The aquatic vertebrate fauna includes shark teeth, rays, crocodiles, turtles, and sea cows. Northwards and upwards in the succession invertebrates are common. They include oysters, Bryozoa, echinoids, and foraminifera. Bioturbation structures include Thalassinoides, Ophiomorpha and Caegichnus groups as well as Scutella trails. The palaeocurrent indicators suggest a dominant northward flow direction and weak east, west, and southern flow components.

Estuarine Facies The estuarine channel facies generally occur in three stratigraphic levels in Jabal Zaltan. Sediments are either variegated coloured, friable, wedge-trough cross-bedded sands and shales associated with fluvial and tidal flat deposits, or consist of well-indurated, parallel-trough, cross-bedded calcareous sandstone forming the base of the marine sections to the north. They also occur in the open marine delta marl facies as thin small-scale cross-bedded calcareous sandstone shoestrings. Fossil content indicates terrestrial as well as marine influences. Silicified tree trunks, bone fragments, and reworked carbonate lithoclasts form a basal lag in fining-up

Lagoonal Facies According to their association with other facies the lagoonal deposits range from yellowish-orange to green-gray, as

Figure 2. North-south cross-section of the Marada Formation illustrating a mosaic of vertical and lateral facies distribution, geometry, and their stacking architecture. It also shows sequence stratigraphic attributes of systems tracts and surfaces. These are the lowstand (LST), the transgressive surface (Ts), transgressive systems tracts (TST), the maximum flooding surface (Mfs), the highstand systems tract (HST) and the upper sequence boundary (SB). The lower boundary is exposed to the west out of the area of study.

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Figure 3. Detailed facies cross-section along Dur Zaqqut escarpment (section D4 in Figure 1), showing the barrier bar and lagoonal facies association of the transgressive systems tract. The association is followed by the condensed section. Note the changes of the barrier facies geometry during the maximum flooding phase, as well as the development of the Echinolampas marker, hardground, and associated Crassostrea oyster growth. their lithology changes from sandy to calcareous shale. The former usually grade from the calcareous sandstone channels. The latter are associated with the barrier bar deposits. Units are 0路5 to 8 m. thick, contain calcareous nodules and deep desiccation cracks filled by secondary gypsum or celestite. Crassostrea oysters commonly form biohermal build-ups. Localised patches of coralline red algae and corals are found in argillaceous limestone and marl

beds where Bryozoa, echinoids, and foraminifera are common. The lagoonal facies were deposited under a broad range of salinities because of their position between the fluvio-estuarine and marine environments. Barrier Bar Facies The barrier bar facies occur below the Echinolampas key horizon (Figures 2 and 3). They consist of white to very pale

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orange, moderately indurated, and porous bioclastic lenticular-shaped complexes measuring up to 20 m thick, 50 km long, and 25 km wide. These bodies are connected by grainstone and packstone sheets. Individual retrograding lenses often encased in shale are about 4 m thick, 150 m long and 50 m across. In places, bar-top surfaces are occupied by oysters, corals, and coralline algae, or are followed by bioturbated and dolomitised mudstone facies. Barrier bodies rest on an erosional contact followed by bioturbated skeletal wackestone and packstone unit overlain by one or several cross-bedded grainstone and packstone units. Skeletal grains are coarse fragments and complete shells of b r y o z o a n s , e c h i n o i ds , m o l l u s c s , foraminifera and calcareous green and red algal rhodoliths. Cross-bedding in barrier bars suggest north-south bipolar palaeocurrents flow direction.

coarsening-up wedges and sheets consisting of multiple sets of trough cross-beds or low angle foresets. Palaeocurrent indicators suggest bipolar flow direction with a dominant northern ebb-flow direction. Intertidal Facies The intertidal facies are 0.5 to 5 m thick units that overlie the grainstone and sandy grainstone units of the barrier â&#x20AC;&#x201C; inlet complex to the north. They are interbedded with the siliciclastic section to the south. It consists of yellowish-brown to yellowishgray, mottled, dolomite to dolomitic mudstone, wackestone, and pelletal packstone, but units exposed in Jabal Zaltan are sandy. Beds exhibit gradual change from lighter to darker colours towards the top where burrows are enlarged by meteoric water dissolution. Sedimentary structures range from massive bedding with a mottled rubble appearance (due to preferential dolomitisation in burrows) to lamination with micro-graded bedding and small-scale cross-lamination.

Tidal Inlet â&#x20AC;&#x201C; Delta Facies The tidal inlet and delta facies occur below, above, or cutting across the barrier facies. They consist of up to 10m of thick, yellowish-grayish orange, mixed carbonate and siliciclastic components. Infill of tidal inlet channels is fining up shoestrings with an erosional base and a lag of reworked limestone cobbles and pebbles, oyster shells, coral debris, and occasional bone and wood fragments. The point bars are either low-angle and unilaterally crossbedded, where beds extend along the channel slope, or form high-angle and trough cross-bedding sets. The channel trough itself is filled by small-scale crossbedded and laminated sand, silt, and shale. Tidal deltas on the other hand are

Marine Bank Facies The marine bank facies consist of soft, white to pale-orange wackestones. These attain flat lenticular and sheets geometry that extends laterally for tens of kilometres and reaches up to 6 m in thickness (Figure 2). Beds are 10 cm to 3 m thick with sharp to erosional basal contacts and sharp upper surfaces that in places grade into green marl. The wackestone consists of ill-sorted shells and fragments floating in a muddy matrix. Allochems consist of bivalve shells, bryozoans, echinoids, coralline red algae, foraminifera and ostracodes. Echinolampas sp. occurs in a

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recognize these members as vertically stacked lowstand (LST), transgressive (TST) and highstand (HST) systems tracts in a second order sequence (Figure 2).

marker horizon at the base of the open marine section, whereas Laufa and Crassostrea oysters develop shell banks together with bored and burrowed hardgrounds on top of some wackestone units. Trace fossils include Thalassinoides and Ophiomorpha and worm burrows (Figure 3).

Bounding Unconformities The Marada Formation rests on the Oligocene with an unconformable erosional boundary exposed west of the Marada Oasis (Figure 1). The top the sequence, on the other hand, is bound by a second disconformity surface that was used as a datum for correlation by Selley (1969) and El-Hawat (1980). It is overlain by a recrystallized limestone unit where the ostracode Paijenborchellina libyca and associated fauna of Borelis melo, Calcarina calcari, Elphidium macellum, E. crispum, Rotalia papillosa and Ammonia beccari were extracted. This suggests a Late Miocene age (Szczchura, 1980). The unconformity has a regional significance throughout North Africa (El Hawat, 1998), and the overlaying unit correlates with Formation â&#x20AC;&#x2DC;Mâ&#x20AC;&#x2122; in the Sahabi area (Muftah et al., this volume) and the basal transgressive unit in Wadi al Qattarah Fm in Al Jabal Al Akhdar (El Hawat and Salem, 1987).

Marine Delta Facies The marine delta facies consists of centimetre- to metre-thick, green to brownish-gray units of marl, sandy marl, and argillaceous limestone. These occur in an irregular wedge geometry and in sheets interbedded with and encasing the open marine wackestone bank deposits. They exhibit sharp to gradational and locally erosional basal contacts. Associated fauna in the marls includes bryozoans, echinoids, ophuroids, foraminifera, ostracodes, and Crassostrea and Ostrea shell banks. Vertebrate bones and silicified wood fragments are found in the sandier marl units. These units are up to 5 m thick, laminated or gently inclined at a 5Â° angle. These are associated with up to 3-metrethick calcareous sandstone shoestrings, and grade laterally into a 20-cm to 2-m-thick bioturbated calcareous green marl that shows gradation wackestone facies.

Lowstand Systems Tracts Facies of the lowstand system tracts consist primarily of fluvial and estuarine sands exposed at the southern foothills of Jabal Zaltan and their lateral equivalents to the north. These were deposited during the initial stages of the Middle Miocene sea rise (El Hawat, 1980). Sea level rise and associated drowning of rivers caused a high rate of sedimentation of fluvio-estuarine sands and shale.

Sequence Stratigraphy El Hawat (1980) was able to subdivide Marada Formation stratigraphy into three distinctive correlatable informal depositional members, assigned to a lower estuarine, a middle lagoonal-barrier and an upper open marine complexes that are correlatable to the siliciclastic succession in Jabal Zaltan. Utilising modern sequence stratigraphic criteria it is possible to

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bars, spasmodic terrigenous influx and sedimentation resumed as prograding marly deltaic fans and associated sand channels directly to the shelf area.

Transgressive Systems Tracts The transgressive system tract is marked by thick lagoonal shale sedimentation in Jabal Zaltan (Figure 2). Changes in the base level and trapping of terrigenous clastics in the nearshore zone allowed high carbonate productivity in terrigenous-free offshore areas. Detrital carbonate bodies were transported landward under highenergy conditions to form barrier bars that separated the source of terrigenous clastics from the open marine areas by forming intermediate lagoons. In the latter, deltas, tidal deltas, and washover fans as well as shales were deposited. Meanwhile, barrier carbonate bodies are stacked in a retrograde-prograding stratigraphic architectural pattern in response to spasmodic increase of siliciclastic influx during transgression. As the sea-level rise reached maximum flooding the open marine facies advanced over the barrier-lagoonal complex forming a condensed section (CS). This was marked by the change of the barrier geometry, hardground development, initiation of oyster bank build-ups, and the spread of the Echinolampas marker (Figure 3). Meanwhile, carbonate sedimentation marking the event extended landward to the terrigenous-dominated tidal flats in Jabal Zaltan to the south, and Qarat Jahannam to the west.

Carbonate-Siliciclastic Cyclicity: Tectonic Signatures Overprinting Eustasy The Marada Formation is a classic transgressive sequence that follows the pattern of unconformity, basal transgressive fluvio-estuarine sand, lagoonal barrier complex, and open marine sedimentation, followed by unconformity (El Hawat, 1980). These are represented by the system tracts discussed above. The Marada sequence constitutes six main depositional genetic units consisting of alternating carbonate and terrigenous clastics. Each unit follows a pattern of a basal transgressive ravinement followed by bioturbated conglomeratic wackestone. This pattern suggests that initial transgression occurred and was followed by a depositional pause before the cross-bedded sets of skeletal grainstone of the barrier body built up. This was followed by early lithification, coralline or algal boundstone encrustation, followed by shale deposition. Clearly these retrograde carbonate units were deposited during phases of marine transgression and temporary still stand. Siliciclastic influx and sedimentation of the lagoonal shale on the other hand, is a regressive event. Whereas the system tracts of the Marada sequence were developed in response to a steady Miocene sea level rise, it was punctuated by regressive events that led to cyclical siliclastic influx and sedimentation.

Highstand Systems Tracts As the sea-level rise started to slow down, sedimentation of the highstand system tract was dominated by wackestone carbonate bank building up in the open marine area. Also, in the absence of barrier

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Geology of Libya (eds M.J. Salem and M.T. Busrewil), London, Academic Press, II, 427-448.

The regressive process was triggered by spasmodic tectonic pulsation that dominated the Sirt rift complex during Miocene time. Cenozoic palaeogeographic maps of the Sirt basin suggest a progressive eastern shift of palaeoshorelines and increased clastic input during the Miocene (El Hawat and Argnani, 2001). This was associated with the ENE tilt of the basinal axis and increased subsidence in Ajdabiya trough (Hallett, 2002). It was also timed with the regional uplift of the African plate, and the domino tectonic effect precipitated by the advancing Atlas Mountain thrust belts from the west that started in the Eocene (El Hawat, 1997; El Hawat et al., in press). However, the tectono-thermal uplift and the associated volcanic activities at Jabal al Souda and Al Haruj al Aswad on the western side of the basin must have had the most profound and direct impact on cyclicity during Miocene sedimentation in Sirt Basin. Meanwhile, the savanna climatic conditions suggested by the vertebrate fauna, if to be considered, must have played a secondary role in the periodic siliciclastic influx during the Miocene eustatic sea level rise.

EL HAWAT, A.S. (1997). Sedimentary basins of Egypt: an overview of dynamic stratigraphy. In: Sedimentary Basins of the World. African Basins. (ed R.C. Selley). Elsevier, Amsterdam, 3, 35-81. EL HAWAT, A.S. and ARGNANI A (2001). Libya and the Pelagian shelf. In: The Palaeotectonic Atlas of the PeriTethyan Domain (eds G. Stampfli, G. Borel, W. Cavazza, J. Mosar and P. Ziegler). CDROM. The European Geophysical Society. Web site: http://www.sst.unil.ch/igcp_369/ default369.htm. EL HAWAT, A.S., JORRY, S., CALINE B., MASSE, P., DAVAUD, E. (in press). The Ypresian-early Lutetian facies, sequences and unconformities of Cyrenaica: their correlation and implications in North Africa. Proc. Eastern Libya Sedimentary basins conference, ESSL, Tripoli. EL HAWAT, A.S. and SALEM, M.J. (1987). A case study of the stratigraphic subdivision of Ar-Rajmah Formation and its implication on the Miocene of Northern Libya. In: Proc. VIIIth Int. Cong. Med. Neogene Stratigraphy, Budapest. Ann. Inst. Geol. Publ. Hungary, Budapest, LXX, 173-184.

REFERENCES DESIO, A. (1935). Studi .geologici sulla Cirenaica, sui deserto Libico, sulla Tripolitania e sui Fezzan Olientale. Missione scientifica della R. Accad. d'ltalie a Cufra, (1931), Roma., 1. 480p.

HALLETT, D. (2002). Petroleum Geology of Libya. Elsevier, Amsterdam. 503 p.

EL HAWAT, A.S. (1980). Carbonateterrigenous cyclic sedimentation and palaeogeography of the Marada Formation (Middle Miocene), Sirt Basin. In: The

PICKFORD, M. (1991). Biostratigraphic correlation of the Middle Miocene mammal

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locality of Jabal Zaltan, Libya. In: Third Symposium on the Geology of Libya (eds M.J. Salem, O.S. Hammuda and B.A. Eliagoubi). Elsevier, Amsterdam, 4, 14831490. PRINCIPI, P. (1932). Osservazioni su alcuni lagni fossili della Libia. Boll. Soc. Geol. Ital. 33, 311-290. SAVAGE, R.J.G and HAMILTON, W.R. (1973). Introduction to Miocene mammal fauna of Jabal Zalten, Libya. Bull. Brit. Mus. Nat. Hist., Geol. 22, 515-527. SAVAGE, R.J.G. and WHITE, M.E. (1965). Two mammal faunas from the Early Tertiary of Central Libya. Proc. Geol. Soc., London. 1623, 89-91. SELLEY, R.C. (1969). Nearshore marine and continental sediments of the Sirte Basin, Libya. Quart. Journ. Geol. Soc. 124, 419460. SZCZCHURA, J. (1980). “Paijenborchellina” Libyca sp. n. from the Upper Miocene of Libya. Acta Palaeontologica Polonia 25 (2), 225-232.

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A Contribution to the Stratigraphy of Formations of the As Sahabi Area, Sirt Basin, Libya AHMED M. MUFTAH, FATHI M. SALLOUM, MUFTAH H. EL-SHAWAIHDI, and MOHAMED S. AL-FAITOURI

ABSTRACT The As Sahabi area of the northeast Sirt Basin is a promising research area for its treasure of Neogene vertebrate fauna that aids in understanding evolution and palaeoenvironments. This region witnessed a number of research activities in the past using different approaches. The present study reviews the stratigraphy of the exposed formations in the As Sahabi region based on sedimentological character and palaeontological content. These rock units are called Formation "M", Formation "P", and the Sahabi Formation, with its seven members: T, T.x., U1, U-D, U-2, V, and Z. A number of stratigraphical/palaeontological markers can be used as signals for picking up the different rock units in the field. These key markers are of great value in local and/or regional correlation. The presence of the microfossils Cytherelloides and Borelis melo in Formation "M" are suggestive of a shallow and warm marine environment, with a temporary reefal condition also developed locally. It is followed by an evaporitic regression associated with the deposition of Formation "P". Finally, the Sahabi Formation started with a transgression, passing to littoral and lagoonal sedimentation, and ending with deltaic and fluviatile deposits, with a local carbonate bar hypothesized during the deposition of the U-D Member.

Ahmed M. Muftah, Fathi M. Salloum, Muftah H. El-Shawaihdi, and Mohamed S. Al-Faitouri, University of Garyounis, Faculty of Science, Department of Earth Sciences, P.O. Box 9480, Benghazi, Libya, a_muftah@yahoo.com, Fathi-salloum@lttnet.net, shawaihdi@yahoo.com, and alfaitouri@yahoo.com

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INTRODUCTION

sections together with the rock samples (cores and cuttings) are housed in the Department of Earth Science of the University of Garyounis. Photomicrographs of some selected specimens were taken with an Olympus-BX41 petrographic microscope attached with DP12 photographic system at the Geological Laboratory of the Arabian Gulf Oil Company. The As Sahabi region was the subject of several studies in the fields of vertebrate palaeontology and stratigraphy during the years 1931-2007, and the following papers are advised as background: Barr and Walker (1970), de Heinzelin and El-Arnauti (1983), ElArnauti and de Heinzelin (1985), Giglia (1984), and D. Boaz (1987).

The data presented here are based largely on previous mapping by de Heinzelin and El-Arnauti (1982). The study area (Figure 1) is located in the northeastern part of Sirt Basin to the West of the Sebkhat al-Qunayyin, about 10km south of Qasr as Sahabi Fort. The map of Sahabi region covers an area of about 400 km2 bounded by longitude 20º 46' to 20º 57' E and latitude 29º 55' to 30º 22' N. The primary objectives of this work are to review the stratigraphy of the exposed rock units in the As Sahabi region, and to interpret the depositional palaeoenvironment based on both faunal and lithological evidence. The previous published and unpublished researches on this region were the cornerstones of this work. Two boreholes were drilled in the As Sahabi region close to Petrocchi locality (Campo d’Aviazione). Borehole 1 (N30º° 01’85.99’’ & E20º46’14.72’’) yielded twelve samples but nine of them were cores with very limited recoveries (total depth is 13.81m). The drilling failed to continue due to technical problems, therefore, the rig moved about 10m nearby to drill Borehole 2. Here drilling extended to 100m, including one core only (59m-60.5m) with 100% recovery. The remaining 32 samples from Borehole 2 were cuttings as indicated and described in Figure 2. These samples were subjected to sedimentological investigation with some palaeontological observation. Seven surface exposures, namely P14, P9, P28, P53, P19 (Sahabi quarry), P66 and P51, were measured and sampled. A number of selected samples have been thin-sectioned. These thin-

LITHOSTRATIGRAPHY Three stratigraphical formations have been established and informally named by de Heinzelin and El-Arnauti (1982). These are the lowermost Formation "M” (Middle Miocene), that is overlain by Formation "P" (Upper Miocene). The youngest formation is named the Sahabi Formation (Lower to Middle Pliocene), which is further subdivided into seven informal members: T, T.x., U-1, U-D, U-2, V, and Z Members (Figure 3). Giglia (1984) mapped the Ajdabiya area (including the As Sahabi studied area) and suggested a different nomenclature. He termed the lower two rock units the Sahabi Formation, which comprises two members: the Sabkha Al Hamra Member (Late Tortonian–Early Messinian) and the Sabkha

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Figure 1. Location map and geological map (Scale 1/2200) of the As Sahabi region (after de Heinzelin and El-Arnauti, 1987) 35

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Figure 2. Composite lithological log of Boreholes 1 and 2, As Sahabi area

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Figure 3. Schematic stratigraphic section of the Sahabi Formation and related Formations "P" and "M" 37

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Al Qunayyin Member (Messinian) The latter presents a its heteropic Wadi Al Farigh Member (Messinian) overlain by the Qarat Weddah Formation (PliocenePleistocene). The above-mentioned nomenclatural discrepancy should be re-assessed. The Qarat Weddah Formation of Giglia (1984) is termed in this study the Sahabi Formation with its included members, in accordance with de Heinzelin and El-Arnauti (1982). The terminology “Sabkha Al Hamra Member” and “Sabkha Al Qunayyin Member,” with its age-equivalent “Wadi Al Farigh Member,” of the Sahabi Formation of Giglia (1984), is not followed in this paper.

FORMATION “M” Lithology Formation “M” consists of semiconsolidated sandy bioclastics with an exposed thickness reaching up to 10m. The nature of the lower boundary is unknown. In the subsurface, it consists of limestone that is white, creamy, bioclastic, moderately hard, and sandy, with fossil fragments of echinoids, bryozoans, ostracodes, and foraminifers (Figures 2 and 4C-D). A few patches of coral are commonly preserved in this rock unit as isolated reefal buildup (Figure 4A-B). This rock unit was believed to be an age-equivalent of the Marada

Figure 4. Photomicrographs of sediments from Formation “M” (A-D), Formation “P” (E), and the Sahabi Formation (F)

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Figure 5. Photographs of sediments in the Sahabi Formation (left and above right), and Formation “M” (below right) Formation (Desio, 1935), but this study disagrees with this correlation. Rather, it correlates with the lower portion of the Sabkha Al Hamra Member of the Sahabi Formation of Giglia (1984).

misidentified as stromatolites by previous workers. The coralline red algal rhodoliths (Lithothamnium?) (Figure 5C) and the bryozoan fragments are rarely present in surface exposures (Figure 4C). Gypsification is the most common diagenetic process that has affected partially or completely contained fossils such as mollusk and echinoderm shells. This is especially the case closer to the uppermost portion of this formation (Figure 4E). The retrieved benthonic foraminifers from this formation are well to moderately preserved, small milioliids and rotaliids, while the planktonic foraminifers are very rare. The assemblage is dominated by Ammonia beccarii, Elphidium crispum,

Palaeontology: Formation “M” yields abundant invertebrates belonging to mollusks (Ostrea sp., Conus sp., Turrietella spp., and Strombus sp.), echinoids (Clypeaster cf. C. agyptiaca, Clypeaster sp. and less common Echinolampas sp.), sponges, corals (morphotype-1 or Madreporaria? and morphotype-2 [R. Brey, pers. comm., 2007])" (Figure 4A-B). The latter were

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Figure 6. Ostracodes from Formation "M" at P53, sample no. 5. Bar scale = 100 µm for 6-1 to 6-3; 200 µm for 6-4 to 6-9. 1- Neonesidea cf. N. mediterranea (complete carapace); 2- Chrysocythere cataphracta/muricata;(left valve); 3- Aurila sp. (complete carapace) 4- Cytherelloidea sp. (left valve) 5Cytherella cf. C. vulgate (right valve) 6- Neomonoceratina cf. N. laskervi (left valve) 7- Cytheretta sp. (right valve) 8- Pokornyella deformis minor (left valve) 9- Loxoconcha gr. ex. Ovulate (left valve)

Elphidium sp., Quinqueloculina spp., Operculina sp., Amphistegina sp. and Borelis melo. There are nine identified ostracodes including Neonesidea cf. N. mediterranea, Chrysocythere cataphracta/ muricata, Aurila sp., Cytherelloidea sp., Cytherella cf. C. vulgate, Neomonoceratina cf. N. laskervi, Cytheretta sp., Pokornyella deformis minor, and Loxoconcha gr. ex. ovulata (Figure 6). Willems and Meyrick (1982) previously reported common Ammonia and Quinqueloculina in this rock

unit with a few small rotaliids, milioliids, and textularids. Formation “M” was deposited in a shallow, neritic, marine environment under warm conditions as evidenced by the presence of microfossils Borelis melo and Cytherelloidea sp. (Figure 6-4) in addition to corals. Age The presence of Borelis melo (i.e. “Neoalveolina” melo zone of Souaya, 1961) is indicative of a Vindobonian age in 40

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coeval to the upper portion of the Sabkha Al Hamra Member and the lower portion of Sabkhat al Qunayyin Member of the Sahabi Formation of Giglia (1984). Based on lithological features, it was deposited under supratidal to marginal environments.

the Mediterranean region. Agip’s geologists also consider this species as a Tortonian age indicator. Based on the integrated calcareous nannofossils and foraminifers (Muftah et al., this volume) the age of this formation is Late Miocene (Tortonian) rather than Middle Miocene as suggested by the previous workers.

Age Formation "P" is dated as Late Miocene (Tortonian) based on the integrated calcareous nannofossils and foraminifers (Muftah et al., this volume) rather than Late Miocene (Messinian) as suggested by the previous workers.

Formation “P” (equivalent to the gypsum facies of Wadi al Qattarah Formation) During Messinian times, the remnants of the Tethys became isolated from the Atlantic Ocean and led to precipitation of thick salt and gypsum evaporites with intercalation of dark sand and clay (de Heinzelin and El-Arnauti, 1982). The water was lowered as much as 2000m and replaced by supersaline and brackish lakes (Hsü et. al., 1973). The present authors agreed to correlate this formation with the gypsum facies of Wadi al Qattarah Formation.

Sahabi Formation The Sahabi Formation has been subdivided by de Heinzelin and El-Arnauti (1982) into the following seven informal members (From bottom to top): Member T It consists of sands with macrofossils in some places, belonging to Gryphaea or to vertebrates (sirenian skeletons and teeth) in addition to bioturbation activity. Shallow cracks have been developed towards its base, remarkably filled with large gypsum crystals. Close to its top the unit is crossbedded (Figure 5A). It is deposited under shallow marine to littoral environments, or more specifically as brackish estuaries and lagoons (El Arnauti and Sogher, 2004).

Lithology Formation “P” presents a lattice of gypsum crystals in a very sparse mineral matrix, with intercalation of dark sand and clay. This formation is characterised by large and deep vertical cracks (>5m in depth) filled with gypsum (de Heinzelin and El-Arnauti, 1982; Figure 2). In the subsurface, it consists of greenish-dark gray, soft, calcareous, pyretic clay, with microfossils The clay grades to dolomite which is light gray, moderately hard, and slightly argillaceous, with gypsified pelecypod molds (Figure 2). Interbedded are white, friable, fine–medium grained sandstones. There is some coarse-grained, sub-angular to rounded, poorly sorted, calcareous sandstone. This formation is

Age Member T of the Sahabi Formation is dated as post-Messinian to Early Pliocene Member T.x. A remarkable clay horizon of a few metres thick (Figure 5B) which is preserved 41

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at a few localities in the northern portion of sector 3B at P66 and P66W (de Heinzelin and El- Arnauti, 1983 and 1987). This unit is reddish brown in colour and exhibits extensive micro-fractures accompanied with slickensides. Very rare vertebrate remains (teeth) are reported.

bioturbation. The retrieved foraminifera include Ammonia beccarii, Elphidium spp., Amphistegina sp. and Discorbis sp. (Figure 4F) as well as macrofossils (bryozoan and echinoderm debris), all indicative of a transgressive carbonate barrier bar (A. ElHawat, pers. comm., 2007).

Member U-1 This level is represented by limited exposures scattered between the older Members T or T.x. and the younger members U2 or U-D of the Sahabi Formation. It consists of loose sand with green to grey clay intercalations and occasional deep pink clay lenses. This rock unit yields common to abundant wellpreserved bones, including teeth of land and marine mammals. It is deposited in tidal channels along shallow sandy coasts (de Heinzelin and El-Arnauti, 1987). In this unit silicified wood is accepted as in situ, at least partially in forms of internal sandstone casts of large tree trunks that are aligned in approximately an E-W trend. This sandstone consists of clean, white, and coarse-grained sand exhibiting planar crossbedding.

Age Member U-D of the Sahabi Formation is dated as Early Pliocene, based on benthonic foraminifers and the stratigraphical position. Member U-2 Extensive bioturbation is present at P73 (de Heinzelin and El- Arnauti, 1987). Also reported at many places, this bed is considered a vertebrate marker bed throughout the whole region. It consists of sand intercalated with clay and thin dolomitic crusts, which generally comprise two main dolomitic beds. The lower one is usually strongly bioturbated and contains decalcified shell beds of mollusks (Figure 4). Fish and whales are also reported. A marine bed of decalcified Gryphaea has been reported in the middle part (de Heinzelin and El- Arnauti, 1987). This unit is represented by a narrow discontinuous strip extended between the older Member U-1 and the younger Member V of the Sahabi Formation. It becomes wider in the lower sectors. It was deposited under lagoonal to shallow neritic waters (de Heinzelin and El-Arnauti, 1987).

Member U-D It is composed of cross-bedded sandy dolomite, highly bioturbated at some places. It is preserved only in the marginal area between sectors 4D and 4C (the maximum thickness of 2 m is at P14). It is interpreted herein as a marine deposit rather than a continental dune as previously suggested. This fact is due to the sandy dolomite type of lithology with extensive

Member V This unit consists of variable white to green sands and sandy clays with lenses

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of gray dolomite, gypsum crystals, and frequent clay balls. The sand grains are usually medium to coarse in size and gravelly to conglomeratic at some places. The lower part is characterised by mammal bones generally included in channels of coarse to gravelly sand. The original discovery of the Stegotetrabelodon skull is in this level. Characteristic are laminated sand and clay of channels, and gypsiferous sands and clays with brackish water molluscs. In the upper part, bones are scarce and rolled. The silicified wood has been found in two main sites; the lower one is slightly above U-2 and the upper one is about 15m-20m higher. Both sites exhibit the same state of preservation (de Heinzelin and El- Arnauti, 1987). This unit is represented by discontinuous exposures between the older Member U-2 of the Sahabi Formation and the recent dunes. The lower unit of Member V (i.e. V-1) is deposited under lagunal conditions, while the upper unit of Member V (i.e. V-2) consist of tidal channel deposits (de Heinzelin and El-Arnauti, 1987).

Stratigraphical Marker Events in the As Sahabi Area Echnofacies Biomarkers There are two surfaces of trace fossil activity indicated by a burrowing level or bored hard ground. Both may indicate a marine transgressive period. Bioturbation Extensive bioturbation activities are reported at P73 (de Heinzelin and El Arnauti, 1987). Extensive burrowing is reported and used as a biomarker bed for the base of U2 of the Sahabi Formation in the whole region. The dwellers here are pelecypods, while the echinoid dwellers left their marks on Formation "M". The other interesting traces are the vertebrate coprolites which flourish in Member U1. Perforated Hard Ground The topmost crust of Formation â&#x20AC;&#x153;Pâ&#x20AC;? exhibits a remnant of weathered perforated hard ground. There are large-sized borings (1.5cm in diameter) and small-sized borings (a few mm in diameter) which were made in dolomitic sandstone crust by the dweller Lithophaga sp.

Member Z This member is a thin crust of very complex fossil soil (palaeosol) capping the Sahabi Formation, with several stages of concretions, crusts, and cracks. Concretions sometimes include shells of Pulmonata. This member might be considered as an independent formation. It is represented by a few scattered exposures capping the highest points of some hills, usually in the in the middle portion of the area. It is believed to be a result of subaerial continental weathering.

Vertebrate Biomarkers Vertebrate remains (i.e. complete skeletons, bone fragments, and teeth) have been collected from the Sahabi Formation Members T, U-1, U-2 and V. These remains belong to fifteen vertebrate families, in which the majority belong to Carnivora among Mammalia, with a few Reptilia and Aves.

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barrier bar rather than a subaerial dune as previously suggested. From the present study it may be proposed that Formation "M" and Formation "P" be lumped into a single rock unit rather that two rock units. There is no unconformity surface observed in the field and they possess the same fauna and flora, suggesting a continuous sedimentation without any break. Therefore, the nomenclature should be addressed in accordance to the Libyan Earth Science Society (ESSL). A shallow warm marine environment is suggested for Formation "M" based on the presence of Cytherelloides, Borelis melo, and corals. It is followed by a Messinian regression associated with the deposition of Formation "P". The Sahabi Formation reflects a transgression passing to littoral and lagoonal sedimentation that ended with deltaic and fluviatile deposits. A number of geological events, key horizons or biomarkers (of local or regional scale), have been recognized in the area which can be used as correlation tools. These include polygonal cracks, bioturbation, fossil wood, vertebrate remains, and invertebrate remains.

Invertebrate Biomarker The co-occurrence of common echinoids-gastropods-pelecypods is considered as a marker assemblage of Formation "M" if it is in situ. The sparse presence of this assemblage in Formation "P" is due to reworking as suggested by partly or completely gypsified or corroded shells. Fossil Wood Biomarker Silicified wood horizons are found at two distinct stratigraphic levels of the Sahabi Formation (Members U1 and V1) which are used locally as good biomarkers. They exhibit mineral replacement (gypsum, quartz and chalcedony). A gypsified fossil wood horizon is found in Formation "P". Cracks-Filled-with-Gypsum Marker Horizon The unconsolidated Formation "P" is cut by deeply polygonal fractures which were filled later by gypsum. Similar cracks, but of shallower depth, are also reported in Member V1, Sahabi Formation (Figure 4). Cross-bedded Marker Bed A distinctive cross-bedded, extensively bioturbated deposit with both planar types of cross-bedding, is used as a marker horizon to define Member U-D of the Sahabi Formation on a local basis, as in P14.

ACKNOWLEDGEMENTS We would like to thank Prof. A. ElArnauti and the late Prof. J. de Heinzelin who are the focal source of this paper. We are also grateful to Prof. A. El-Hawat for the valuable discussion on some parts of the paper. Thanks are also extended to Mr. G. Coles for reviewing the ostracode plate. Thanks are due to Mr. A. Salama for thin section preparations, J. Davy for his technical help with the SEM and photography, and Mr. W. El-Bargatie for

DISCUSSION AND CONCLUSIONS The Neogene deposits of the As Sahabi area are represented by three formations: Formation "M," Formation "P," and the Sahabi Formation. The latter is further subdivided into Members (T, T.x., U1, U-D, U2, V, and Z). Member U-D is proved to be a carbonate transgressive 44

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Geology of Sahabi, (eds N.T. Boaz, A. ElArnauti, A. Gaziry, J. De Heinzelin, and D.D. Boaz.), Alan R. Liss, New York, 1-21.

drafting some of the figures. Finally we would like to express our sincere gratitude to University of Garyounis Research Centre and to the East Libya Neogene Research Project (ELNRP) which have funded field trips, attendance expenses, and editorial effort.

DESIO, A. (1935). Studi geologici sulla Cirenaica, sul Deserto Libico, sulla Tripolitinia e sul Fezzan Orientale: Missione Scintifica della R. Accad. d'Italia a Cufra 1, 480 p.

REFERENCES BARR, F. T. and WALKER, B. R. (1970). Late Tertiary channel system in northern Libya and its implication on Mediterranean Sea level changes. In: Initial Rep. Deep Sea Drill. Proj. (ed A. G. Kaneps), XIII (2), 1244-1251.

EL-ARNAUTI, A. and DE HEINZELIN, J. (1985). Le Neogene en Libye. Palaeobiologie continentale, Montpellier, 14, 269-282. EL-ARNAUTI, A. and EL SOGHER, A. (2004). Short Notes and Guidebook on the Geology of Qasr As Sahabi Area. Tripoli, Earth Science Society of Libya, 95 p.

BOAZ, D. Dechant (1987). Taphonomy and paleoecology at the Pliocene site of Sahabi, Libya. In: Neogene Paleontology and Geology of Sahabi, (eds N.T. Boaz, A. ElArnauti, A. Gaziry, J. de Heinzelin, D.D. Boaz), Alan R. Liss, New York, 337-348.

GIGLIA, D. (1984). Geological Map of Libya 1:250 000. sheet Ajdabiya, (NH 346), Explanatory Booklet. Ind. Res. Cent., Tripoli, 93 p.

HEINZELIN, J. and EL-ARNAUTI, A. (1982). Stratigraphy and geological history of the Sahabi and related formations. Garyounis Sci. Bull., Spec. Issue 4, 5-12.

HSĂ&#x153;, K. D., CITA, M. B. R. and RYAN, W. B. F. (1973). The origin of the Mediterranean evaporites. In: Initial Rep. Deep Sea Drill. Proj. (Glomar Challenger) 13 (2), 1201-1231.

HEINZELIN, J. and EL-ARNAUTI, A. (1983). Geology of the Sahabi area with a geological map at scale 1:25000. Research Centre Garyounis University, Benghazi, Libya. (Edited by the Section of Cartography and Photo-Interpretation of the Royal Museum for Central Africa, Tervuren, Belgium) in commission of the Research Centre, Garyounis University, Benghazi, Libya. 59 p. with Annexes.

SOUAYA, F.J. (1963). Micropaleontology of four sections south of Qoseir, Egypt. J. Micropaleontology 9, 233-266. WILLEMS, W. and MEYRICK, R. (1982). Preliminary report on the marine microfauna (Foraminifera, Ostracoda) of the Sahabi and related formations in northern Libya. Garyounis Sci. Bull., Spec. Issue 4, 5-12.

HEINZELIN, J. and EL-ARNAUTI, A. (1987). The Sahabi Formation and related deposits. In: Neogene Paleontology and

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Biostratigraphical Notes on the As Sahabi Stratigraphic Boreholes 1 and 2, Sirt Basin, Libya

AHMED M. MUFTAH, ALI A. EL-MEHAGHAG, AND STEVE STARKIE

ABSTRACT Formations “M” and “P” in the As Sahabi region have been previously dated to the Middle Miocene on the basis of foraminifera, ostracodes, and macrofossils. We identify here 19 species of calcareous nannofossils for the first time. We assign these sediments to the Late Miocene (NN10b-NN11b of Martini, 1971) or to the Tortonian – Early Messinian zones. Formation “M” is continuous into the overlying Formation “P” without a sedimentation break. Samples revealed 33 Middle-Late Miocene benthonic and planktonic foraminifers, the foraminiferal tests showing strong gypsification at shallower depths of Formation "P". The overlying Sahabi Formation is barren of any calcareous nannofossils.

Ahmed M. Muftah, University of Garyounis, Faculty of Science, Department of Earth Sciences, P. O. Box 9480, Benghazi- Libya, a_muftah @yahoo.com Ali A. El-Mehaghag, Geological Laboratory, Arabian Gulf Oil Company, P. O. Box 263, Benghazi, Libya, a_mehagnan@yahoo.com Steve Starkie, Datum Stratigraphic Associate Limited, 12 The Meade, Chorltonville, Manchester, M21 8FA, U.K., Steve.Starkie@datumstrat.com

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INTRODUCTION

Previous Work

Location

In general, previous palaeontological investigations of Formation “M” and Formation “P” were based on Foraminifera, Ostracoda and macrofossils, for which a Middle Miocene age was inferred (Willems & Meyrick, 1982; de Heinzelin and ElArnauti, 1982; Willems, 1987). The Sahabi Formation has also been dated by the contained vertebrate and invertebrate remains (see other authors in this volume).

Two boreholes (1 and 2) were drilled in the As Sahabi area, northeastern part of Sirt Basin close to vertebrate localities established by Petrocchi in the 1930’s (N30°01’85.99’’ & E20°46’14.72’’) (Figure 1). Borehole 1 was drilled to a total depth of 13.81m, penetrating clastic Pliocene sediments with no microfossils. Borehole 2 was drilled to a total depth 100m penetrating clastic and calcareous sediments (Figure 2).

Figure 1. Location map of the As Sahabi area. 48

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Figure 2. Distribution chart of calcareous nannofossils in As Sahabi Borehole 2. 49

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MATERIAL AND METHODS reworked calcareous nannofossil taxa were recorded. All taxa can be found, fullyauthored and referenced, in Perch-Nielsen (1985) and Bown and Young (1998). The biostratigraphy is shown in Figures 2 and 3. The biozonation schemes of Martini (1971), Okada and Bukry (1980), and Young (1998) were applied. A number of samples from two stratigraphical boreholes were analysed: Borehole #1 (9 cores and 3 cuttings samples) and Borehole #2 (one core and 20 cuttings samples). All the prepared samples are barren of any calcareous nannofossils except the lower depths of the borehole #2 (72, 80, 86 and 100m), which yielded 29 taxa. Nineteen taxa were of Late Miocene age including Reticulofenestra haqii, R. minuta, Discoaster loeblichii, D. braarudii, D. neorectus, D bellus, D. berggrenii, Helicosphaera carteri var. wallichii, H. stalis, H. wallichii, H. sellii, Coccolithus miopelagicus, C. pelagicus, Sphenolithus moriformis, S. abies, Calcidiscus macintyrei, C. tropicus, Reticulofenestra pseudoumbilicus, and Angulothina arca. Ten taxa were considered as reworked: six of Eocene age including Cyclicargolithus floridanus, Reticulofenestra umbilica, Reticulofenestra bisecta, Micrantholithus hebecuspis, Micrantholithus cf. M. discula, and Lithustromation perdurum, while four were of Late Cretaceous age, including Marthasterites furcatus, Prediscosphaera cretacea, Micula staurophora and Watznaueria barnesae (Figure 3). Most of the calcareous nannofossil taxa exhibit a good to moderate preservation of Late Miocene age. The lowermost portion of the studied section

This study was based on samples obtained from two stratigraphic boreholes (1 and 2). Twelve samples from borehole 1 (0-13.81m) and 21 samples from borehole 2 (14.6-100m) were selected to study the calcareous nannofossils and the Foraminifera. Calcareous nannofossils and Foraminifera were retrieved from the lower horizons. Foraminifera were recorded from 63-100m, and calcareous nannofossils were recorded from 72-100m. The lower two formations “M” and “P” are of particular interest, because they have not been studied previously using calcareous nannofossils. Smear slides were prepared following the pipette strew–slide method described in Bown and Young (1998). Foraminiferal slides were also prepared according to standard micropaleontological techniques. All smear slides were examined with an Axio Plan 2 Universal Zeiss Microscope at 1000x and 2000x magnification. Each slide was examined under crossed polarized and transmitted (Brightfield) light. Estimation of the relative abundance of species present per field of view was based on three traverses. Foraminifers were examined by a Krüss reflected light microscope. All smear slides and foraminiferal slides are housed in the micropalaeontological collections in the Department of Earth Sciences of University of Garyounis, Benghazi, Libya. RESULTS The four investigated samples from Formation “M” yielded moderate to high richness of moderately to well-preserved specimens. Nineteen Late Miocene and 10

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Figure 3. Nannofossil biostratigraphy, As Sahabi Borehole 2. R=rare, C=common, F=frequent, P=present

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range from Middle to Late Miocene, where all of the planktonic foraminiferal zonal markers are absent. The Borelis melo assemblage zone with its two subzones (Dendritina rangi subzone and Archaias aduncus subzone) recognised by Bellini (1969) is used as a Middle Miocene marker in the Al Jaghbub Formation of eastern Cyrenaica. This zone is not applicable in the As Sahabi region due to the different faunal assemblages. The retrieved foraminiferal species exhibit a poor to good preservation (63-100m). Calcite of the tests is seen to be substituted by gypsum, which may be formed by a diagenetic process after evaporation.

(i.e. at depths 86, 94, and 100 m) is assigned to the early Late Miocene (Tortonian) (NN10b of Martini (1971) with modification of Young (2005). This corresponds to CN8b of Okada and Bukry (1980) in accordance with the presence of Discoaster loeblichii and Discoaster neorectus and the first occurrence (FO) of the zonal marker Discoaster berggernii in the above sample (Figures 2 and 3). The sample at depth 80m is assigned to the Late Miocene (Tortonian) (NN11a of Martini (1971) with modification of Young (2005). It corresponds to CN9a of Okada and Bukry (1980) in accordance with FO of the zonal marker Discoaster berggernii and the last occurrence (LO) of Discoaster neorectus. Other recorded taxa such as Discoaster bellus, Discoaster braarudii, Helicosphaera stalis, and Sphenolithus abies (Figure 3) support this age. The zonal marker Discoaster quinqueramus is not present in the samples. The sample at depth 72m is assigned to Late Miocene (Late Tortonian-Early Messinian) (NN11a-lowermost part of NN11b) of Martini (1971) with modification of Young (2005). It corresponds to CN9a and the lowermost part of CN9b of Okada and Bukry (1980) in accordance with the presence of Helicosphaera stalis and Sphenolithus moriformis. The foraminiferal taxa retrieved from Borehole 2 is listed in Figure 4. Present are Globigerinoides trilobus, Gs. Quadrilobatus, and Globigerina nepenthes, with Orbulina universa and O. suturalis. The assemblage reported in the lower sample (86-100m) allows us to give an age

TAXONOMIC REMARKS The identified calcareous nannofossil species, listed below and illustrated in Figure 5 are arranged alphabetically by their specific epithets. Bibliographic references for those taxa are not listed in the references section, but have collectively been presented by PerchNielsen (1985), Young (1998), and Bown (2005). Genus: Angulothina Bukry (1973c) A. arca Bukry (1973c) Genus: Calcidiscus Kamptner (1950) C. macintyrei (Bukry & Bramlette, 1969a) Loeblich and Tappan, 1978 C. tropicus Kamptner, 1956 (sensu Gartner, 1962) Genus: Coccolithus Schwarz ( 1894) C. miopelagicus Bukry (1971) C. pelagicus (Wallich, 1877) Schiller (1930)

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Figure 4. Foraminiferal distribution in As Sahabi Borehole 2 R=rare, C=common, F=frequent, P=present. 53

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Figure 5. Calcareous nannofossil taxa identified from Borehole #2, Formation “M” at As Sahabi

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Genus: Sphenolithus Deflandre in Grasse (1952) S. abies Deflandre in Deflandre & Fert (1954) S. moriformis Bronnimann & Stradner, (1960) Bramlette & Wilcoxon (1967) Genus: Watznaueria Reinhardt (1954) W. barnesae (Black in Black and Barnes, 1959) Perch-Nielsen (1968)

Genus: Cyclicargolithus Bukry (1971) C. floridanus Bukry (1971) Genus: Discoaster Tan (1927) D. bellus Bukry & Percival (1971) D. berggrenii Bukry (1971b) D. braarudii Bukry (1971b) D. loeblichii Bukry (1971a) D. neorectus Bukry (1971a) Genus: Helicosphaera Kamptner (1954) H. carteri var wallichii (Lohmann, 1902) H. stalis (Bukry & Bramletti, 1969a) Jafar & Martini (1975) H. sellii (Bukry & Bramletti, 1969a) Jafar & Martini (1975) H. wallichii (Lohmann, 1902) Bourdreaux & Hay (1969) Genus: Marthasterites Deflandre (1959) M. furcatus (Deflandre in Deflandre & Fert, 1954) Deflandre (1959) Genus: Micrantholithus Deflandre in Deflandre & Fert (1954) M. discula (Bramlette & Riedel, 1954) M. hebecusps Bown (2005) Genus: Micula Vekshina (1959) M. staurophora (Gardet, 1955) Strandner (1963) Genus: Prediscosphaera Vekshina (1959) P. cretacea (Archangelsky, 1912) Gartner (1968) Genus: Lithostromation Deflandre (1942b) L. perdurum Deflandre (1942b) Genus: Reticulofenestra Hay, Mohler & Wade (1966) R. bisecta (Hay et al., 1966) Roth (1970) R. haqii Backman (1978) R. minuta Roth (1970) R. pseudoumbilicus (Gartner, 1967b) Gartner (1969c) R. umbilica (Levin, 1965) Martini & Ritzkowsti (1968)

CONCLUSIONS Twenty-nine calcareous nannofossil species have been identified and illustrated for the first time from the lowermost horizons of As Sahabi Borehole #2 (72100m). These indicate that this part of the borehole is Late Miocene (NN10b-NN11b) in age. This age is supported by the presence of typical Miocene foraminifers including Borelis melo, Orbulina universa, Orbulina suturalis, and Globigerinoides spp. The stratigraphic distribution of calcareous nannofossil species permits the recognition of three calcareous nannofossil biozones, 1) NN10b zone of Martini (1971) with modification of Young (1998), corresponding to CN8b of Okada and Bukry (1980) of Late Miocene age; 2) NN11a zone of Martini (1971), corresponding to CN9a of Okada and Bukry (1980) of Late Miocene age, and 3) NN11a - lowermost part of NN11b zone of Martini (1971) with modification of Young (1998), corresponding to CN9a â&#x20AC;&#x201C; lowermost part of CN9b zone of Okada and Bukry (1980) of Late Tortonian-Early Messinian age.

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RECOMMENDATION

REFERENCES

A s c i e n t i f i c n ome n c l a t u r e committee in collaboration with the Earth Science Society of Libya (ESSL) should be established to sort out the nomenclature in this region. On the basis of the samples obtained from both boreholes at As Sahabi, we recommend additional boreholes to be drilled in this region, with particular care to have good core recovery for stratigraphical and palaeontological studies. One of these boreholes should penetrate and pass into Middle Miocene sediments. Prior to drilling, seismic control is also recommended to better understand and estimate the age of the As Sahabi channelfill (see papers by Nicolai and Drake, et al., this volume).

BELLINI, E. (1969). Biostratigraphy of the "Al Jaghbub (Giarabub) formation" in eastern Cyrenaica (Libya). In: 3rd Afr. Micropaleontol. Colloquium, Cairo, 165183. BOWN P.R. (2005). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4), International Nannoplankton association. Cambridge University Press. J. Nannoplankton Res. 27 (1), 21-95. BOWN, P.R. AND YOUNG, J.R. (1998). Introduction. In: Calcareous Nannofossil Biostratigraphy (ed P.R. Bown). London, Chapman and Hall/Kluwer Academic Publisher,16-28.

ACKNOWLEDGMENTS The authors thank Shell Exploration and Production Libya for financial support, and Arabian Gulf Oil Company (AGOCO) for laboratory facilities, and for the technical assistance of Mr. Adel Altaboni and Mr. Ashur Salama for smear slides and thin-section preparations. Mr. Mohamed Al-Faituori and Mr. Moftah Shawaihdi from Garyounis University are thanked for the field assistance. We would like to express our sincere thanks to Prof. Ahmed El-Hawat for his guidance, help and encouragement during this study. Our gratitude also goes to Mr. Hassan Swalam for his assistance in the field. Finally, very special thanks extend to Prof. Noel Boaz and Prof. Ali El-Arnauti for reviewing the manuscript and providing valuable comments and corrections.

DE HEINZELIN, J. and El-Arnauti, A. (1982). Stratigraphy and geological history of the Sahabi and related formations. Garyounis Sci. Bull., Spec. Issue 4, 5-12. MARTINI, E. (1971). Standard Tertiary and Quaternary calcareous nannoplankton, In: Proceeedings II Planktonic Conference (ed A. Farinacci), Rome, 1970, 2, 739-785. OKADA, H. and BUKRY, D. (1980). Supplementary modification and introduction of code numbers to the lowlatitude coccolith biostratigraphic zonation (Bukry, 1973 and 1975). Mar. Micropaleontol. 5 (3), 221-225. PERCH-NIELSON, K. (1985). Cenozoic calcareous nannofossils. In: Plankton Stratigraphy( eds Bolli, H.M., Saunders

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J.B. and Perch-Nielsen K.). Cambridge, Cambridge Univ. Press. YOUNG, J.R. (1998). Neogene. In: Calcareous Nannofossil Biostratigraphy (ed P.R. Bown). London, Chapman & Hall/ Kluwer Academic Publishers, 225-265. WILLEMS, W. and MEYRICK, R. (1982). Preliminary report on the marine microfauna (Foraminifera, Ostracoda) of the Sahabi and related formations in northern Libya. Garyounis Sci. Bull., Spec. Issue 4, 5-12. WILLEMS, W. (1987). Marine microfauna from Sahabi and related formations. In: Neogene Paleontology and Geology of Sahabi (eds. N.T. Boaz et al.). Alan R. Liss, New York, 83-90.

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Establishment of a Chronostratigraphical Framework for the As Sahabi Sequence in Northeast Libya CLAUS BEYER

ABSTRACT

A chronostratigraphical correlation of Neogene outcrops in the As Sahabi region has been carried out. In addition, the sedimentary sequence was dated by the use of K-Ar dating and palaeomagnetism. The absolute dating of glauconite grains in the lowermost part of the studied shallow marine sequence gave an age of 7.5 â&#x20AC;&#x201C; 7.7 ma. The magnetostratigraphy shows at least 5 polarity zones - 3 reversed and 2 normal. Depending on the degree of continuity, the sequence was deposited during 200,000 to 500,000 years. There are several erosional boundaries which may indicate significant hiati. It is suggested to concentrate further palaeomagnetic studies on the intervals around the polarity boundaries and hiati, which seem to coincide. The best samples were hand specimens from limestones and the lower part of the Sahabi Formation which contains a high content of magnetic minerals probably transported from a volcanic source to the south. These first results may serve as a reference for further studies and demonstrate that the sediments at As Sahabi can be placed in a chronostratigraphical framework that will facilitate understanding of the evolution of the area in Late Miocene time.

Claus Beyer, CB-Magneto, SandvigĂĽ 24, P.O.Box 7015, N-4004 Stavanger, Norway, cb-m@online.no

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INTRODUCTION

fresh as possible and free of secondary magnetic minerals. In addition, the correct orientation, strike, and dip of the samples and of the sampled beds should be recorded. This was measured with a normal compass. Claystone, siltstone, and limestone facies were sampled. Coarser material such as sand, which comprises a large part of the Sahabi Formation, was not sampled since it is unsuitable for palaeomagnetic analysis. Different types of equipment were brought out in the field for taking the samples. Of these the collection of hand specimens and the collection of sediment in small plastic containers were the most successful. Drilling of samples with a water-cooled hand drill was tried but did not work out due to the sediment composition. Collection in U-tubes was also not possible because the sediment was too hard for this method. The sampling was carried out in June, 2007 during a five-day stay in the field. Five important localities were visited and samples were taken from four of them. These were P9, P28, P51, and P53. At P9 the T, U-1, and U-2 members were sampled. At P28 the levels sampled were U-1 and part of U-2 and V. These outcrops offered the opportunity to sample the same sequence at two localities. The sampling of the different lithologies further made it possible to evaluate which ones give the best results and should be sampled in future palaeomagnetic projects in the area. At P53 a profile was sampled in a glauconitic mudstone facies. However, the sediment composition made the sampling of drilled plugs impossible. A hand specimen was sampled instead. This sediment is suitable for magnetic analysis and for K-Ar dating of the glauconite.

This report contains the results of a palaeomagnetic investigation of four of many localities in the As Sahabi area of Libya. The purpose was to obtain chronostratigraphical information about the sedimentary sequence. A restricted number of dating methods is available for sediments of this age (Late Miocene-Pliocene). One of them is palaeomagnetism. Another one is K-Ar dating. Most other absolute dating methods fail on sediments of this age. More traditional marine biostratigraphy may also give some information to the age of the limestones. All of these methods were tried. Only the palaeomagnetism and the glauconite dating gave usable results in this study. FIELD METHODS The outcropping sedimentary sequence at As Sahabi consists of shallow marine, deltaic, and fluvial facies (de Heinzelin and El-Arnauti, 1987). The sampling program was focused on palaeomagnetic analysis. Only the finegrained facies are suitable for such analysis, so the sampling was concentrated on these facies while intervals with sand were omitted. The localities visited were P9 and P28 which were sampled through most of the accessible profiles. Samples from Sahabi Formation units U-1, U-2 and Member T were taken. Two other localities, P53 and P51, were visited to sample Formation M. In addition, other time markers were sought and found. The correct sampling of the outcrops is important and may be quite complicated. The sediment should be as

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Zijderveld plots to facilitate the interpretation. The growth of new magnetic minerals as a result of weathering causes a secondary magnetization, carried by different types of Fe-oxides, and their presence complicates the analysis. While the alternating field method demagnetised most samples, samples containing secondary Fe-oxide minerals had to also be thermally demagnetised to remove this secondary magnetisation. A combination of the two methods was required when the results were ambiguous and in a few cases a final result could not be obtained with any certainty. Thermal demagnetisation does not only remove the secondary magnetisation but also partially the primary one. Correct demagnetisation is therefore a balance between the two methods. Despite this complication, a reasonably clear picture of the polarity in the sampled intervals emerged. Although many of the samples are considered poor palaeomagnetic samples according to standard quality requirements, the magnetic polarity gives a usable stratigraphic result.

LABORATORY METHODS The magnetic polarity of the samples was determined after restoring the samples to their orientations in the field. In the laboratory the samples were cut, cleaned, and measured in the magnetometer. The samples were then demagnetised by alternating field method in steps of 25 Oe up to 200 Oe and thereafter in steps of 50 Oe and 100 Oe above 400 Oe for the samples which were demagnetised that much. Generally, the magnetic susceptibility of the sediment is very low, limiting problems with remagnetisation, except for the recent growth of weathering products. Also the magnetic intensity was low for most samples, being in the range 0.05 â&#x20AC;&#x201C; 0.50 mA/m. On the other hand, a couple of samples were extremely magnetic with a magnetic intensity of over 50 mA/m and a very stable magnetisation. These samples were from a bed interpreted as an ash bed occurring at the bottom of P28. The magnetic data were displayed in stereonet, intensity decay plots, and in

Figure 1. Intensity Decay plot (left) , directional plot (centre), and Zijderveld plot, of demagnetisation (right) of sample 12 from As Sahabi Locality P9

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global polarity scale, thus dating the sequence. Figure 2 shows the site of sampling in Formation M at Locality P53. Formation M showed normal polarity (Figure 3). Glauconite was discovered in the palaeomagnetic samples from P53 (Figure 4). It was dated by the K-Ar

RESULTS Examples of typical demagnetisation behaviour are shown in Figure 1. The most frequently used plots are intensity decay plots and stereographic projections of directions where the negative inclinations are plotted on the upper hemisphere as open circles. In some examples Zijderveld plots are also used to display the data. This plot displays a vertical and a horizontal projection of the directions with the distance from the centre indicating the intensity. The geographical location of the profiles is approximately 30째 N. In Messinian times it was almost the same since Africa has not moved much northward during the last 6 million years. The inclination for a sample magnetised at 30째N is 49째. It is positive for normal polarity and negative for reverse polarity. The inclination alone thus cannot be used for dating of the sequence. A local magnetic polarity scale over a longer sequence may, however, in combination with other data, lead to a correlation with the established

Figure 3. The lowermost part of the studied sequence is comprised of shelf and nearshore marine sediments outcropping at localities P53 and P51, respectively. One hand specimen was collected from each locality. P53 was rich in glauconite grains.

Figure 2. Formation M as exposed at P53. This is a marine shelf deposit and the stratigraphically lowest sediment of the studied sequence.

Figure 4. Glauconitic grains recovered from sediments of Formation M at P53

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method (Appendix 1). The result of three analyses were 7.5, 7.6 and 7.7 ma with an uncertainty of 0.3 ma.

Figure 5. A hard crust indicates a possible erosional boundary to the thin U-1 unit which is overlain by the U-2 limestone. The U-2 limestone and part of the U-1 sediment were suitable for palaeomagnetic analysis. In the profile sampled at Locality P9 much of the sandy sediments of Member T were unsuitable for palaeomagnetic analysis. Figure 5 shows the capping U-2 limestone and underlying U-1 at P9 that were analysed. Figure 6 summarises palaeomagnetic results from P9. A second palaeomagnetic profile in the Sahabi Formation was analysed at Locality P28 (Figure 7). An ash bed was discovered in the lower portion of this profile (Figure 8). The data from the ash bed shows a very stable magnetisation which could not be removed by the alternating field method. Thermal demagnetisation to above 600째C removed much of the magnetisation and to 685째C removed all magnetisation. It indicates that

Figure 6. The sample levels and the interpreted magnetic polarity zones at locality P9.

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Figure 7. Sample levels and magnetostratigraphy at P28. A large number of the samples gave ambigious results. The best samples were from the bottom of the profile and from the limestone unit U2.

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acquisition at palaeolatitude 30.79 N and a Virtual Geomagnetic Pole (VGP) at 86.5 N and 100.1 E. (A VGP is calculated from data from one point in space and time while a palaeomagnetic pole position is calculated from the mean direction of several VGPs). In comparison to this, a typical sample of a mudstone facies shows much weaker magnetisation and the scatter of the directions is much larger. INTERPRETATION

Figure 8. The strongly magnetic bed which is interpreted as a redeposited tuff in the fluvial facies. The fabric shows an WSW-ENE orientation of the long axes indicating a current direction towards ENE.

To the left in Figure 9 is shown the local magnetic polarity scale (MPS). Whether N1 should be split into two normal polarity zones cannot be determined without knowing the boundary between the P and M formations. If erosional, some time may not be represented and there may be an undetected reverse polarity zone. It will

magnetite and hematite are the important carriers of the remanent magnetisation. The stable magnetisation of this sample has the direction which corresponds to an

Figure 9. Suggested correlation of the profiles based on magnetostratigraphy. 65

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7.5-7.7 ma. Therefore the studied sequence is correlated to the very latest Miocene as shown in Figure 10. Further work will be needed to choose between these hypotheses and refine the age determination of the Sahabi Formation. A reference section from a core would highly improve the data due to the problem with formation of secondary magnetic minerals during weathering. Samples from a core would not be weathered to the same extent. The ash bed discovered at P28 is a potentially excellent chronostratigraphic marker and it should be located in the other profiles. Magnetic analysis of this bed from different localities will give a reliable VGP position for use in other studies of the Late Neogene tectonics in the area. The exact occurrence of the polarity boundaries should be determined by investigation of the same sequence at other localities in the area. It is probable that the finding of time markers such as the magnetic polarity boundaries, the ash bed, together with the additional absolute dating, will lead to a well documented placement of the sequence into the chronostratigraphic framework . P51 contained no glauconite but this sediment was suitable for palaeomagnetic analysis. Both P51 and P53 should be sampled in the lower, middle, and upper parts to investigate if there is a polarity boundary present.

be necessary to sample a continuous transition zone between the two formations to determine the time interval. The polarity boundary between R2 and N2 coincides almost with the base of U-2. However, two samples, one in P9 and one in P28, place the boundary just above the claystone and beneath the limestone. The time interval represented by the fluviatile unit, U-1 in P28, may be rather short. The incised channel sediment was deposited during the last period of the R2, shown by the reversed polarity. The nearshore facies, Member T, may represent a longer interval. Whether it is a continuation of the P Formation, also interpreted as nearshore facies, or they are separated by a hiatus, is unknown at present. The glauconitic shelf sediment of the M Formation probably represents much more time than the other facies (glauconite is formed during non deposition) unless the glauconite was redeposited. The limestone may also represent a considerable amount of time with marine conditions. CONCLUSIONS The magnetic investigation showed that it is possible to establish a local magnetic polarity scale for this sequence. Based on the magnetostratigraphy, the sedimentary facies, and a tentative correlation with the global sea-level changes, it is suggested that the most likely age of the sequence is Chron 3a or Chron 4, as shown in Figure 10. At present the most updated absolute ages of the polarity chrons are found in Gradstein, et al. (2004) and Haq (2007; Figure 10). The dating of the glauconite gave an age of approximately

ACKNOWLEDGEMENTS In the field I was kindly assisted by Muftah Shawaihdi and Ahmed Muftah, of the Department of Earth Sciences of the University of Garyounis. The laboratory palaeomagnetic work was carried out in

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Figure 10. Two possible interpretations of the palaeomagentic analyses. In A, a time interval of ca. 200,000 years accounts for deposition of Formations M and P and the Sahabi Formation. In B, a time interval of ca. 500,000 years is postulated. Further sampling at a finer stratigraphic scale is necessary to choose between these alternative interpretations.

CB-Magnetoâ&#x20AC;&#x2122;s lab in Denmark. Measurements was made by Pia Buchholtz Hansen and Claus Beyer. The consultancy work on dating of glauconite was carried

out in Krakow, Poland, by Michal Banas, Polish Academy of Sciences. X-ray spectroscopy was done at the physical Institute of Ă&#x2026;rhus University, Denmark.

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Samples were studied for biostratigraphic dating by Erik Thomsen, Geological Institute, Århus, and by Brett Woodhouse, Network Stratigraphic.

GRADSTEIN, F.M., OGG, J.G., and SMITH, A.G. (2004). A Geological Time Scale. Cambridge, Cambridge University Press, 610 p. HARDENBOL, J., THIERRY, J., FARLEY, M.B., JACQUIN, T., DE GRACIANSKY, P.-C., and VAIL, P. (1998). Mesozoic and Cenozoic sequence chronostratigraphic framework of European basins. SEPM Special Publication 60, 3-14.

REFERENCES A NTHONY , J.W., W ILLIAMS , S.A., BIDEAUX, R.A. and GRANT, R.W. (1995). Mineralogy of Arizona. Tucson, University of Arizona Press.

HAQ, B.U. AND VAN EYSINGA, F.W.B. (2007). Geological Time Table. Elsevier, Amsterdam.

BONNEHOMME, M.G., THUIZAT, R., PINAULT, Y., CLAUER, N., WENDLING, R. and WINKLER, R. (1975). Methode de datation potassium-argon. Apareillage et technique. Notes Technique de L'Institut de Geologie Université Louis Pasteur 3, 53 p.

ODIN, G.S., et al. [35 Collaborators] (1982). International standards for dating purposes. In: Numerical Data. In: Stratigraphy (ed G.S. Odin). Chichester, Wiley and Sons, 129-149.

HEINZELIN, J. and EL-ARNAUTI, A. (1987). The Sahabi Formation and related deposits. In: Neogene Paleontology and Geology of Sahabi (eds Boaz, N.T., et al.). New York, Liss, 1-21.

SPEZZAFERRI, S. and TAMBURINI, F. (2007). Palaeodepth variations on the Eratosthenes Seamount (Eastern Mediterranean): Sealevel changes or subsidence? e.Earth Discussion 2, 115-132.

DURAKIEWICZ, T. (1995). Innowacje w aparaturze do wydzielania i oczyszczania argonu („Innovations in the apparatus for extraction and purification of argon”). Materialy Ogólnopolskiej Sesji Naukowej "Datowanie Mineralów i Skal w Oparciu o Rozpad Promieniotwórczy Potasu-40", Lublin, 26-27 października 1995, 38,44, 4453 (in Polish).

STEIGER, R.H. and JAEGER, E. (1997). Subcommission on Geochronology: convention on the use of decay constants in geo- and cosmochronology. Earth and Planetary Science Letters 36, 94-96. WILGUS, C.K., HASTINGS, B.S., KENDALL, C., POSAMENTIER, H.W., ROSS, CCA. and WAGONER, J.C. (1998). Sea-level Changes: An integrated approach. SEPM Spec. Publ. 42.

EL-ARNAUTI, A. and EL SOGHER, A. (2004). Short Notes and Guide Book on the Geology of Qasr As Sahabi Area. Sedimentary Basins of Libya, 3rd symposium. Tripoli, Earth Science Society of Libya.

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AS SAHABI CHRONOSTRATIGRAPHY

APPENDIX 1 K-Ar Glauconite Dating 1. Glauconite separation

The samples were crushed by a thermoelectric disintegrator TD-2 (patented by Durakiewicz and Banas 2001) by Peltier effect. Each sample was disintegrated in about 100 hours. Glauconite was separated by Neodymium+magnet and purified from other clay minerals by ultrasonic-head. The results of the chemical analysis show that the separated material fulfills the criteria postulated by Odin et al. (1982). 2. K determination The monomineral samples were split into two aliquots: a 50 mg for potassium determination and about 50 mg for argon analysis. The 50 mg sample was diluted in a mixture of HF and H2SO4. The solution was evaporated in a steam bath and once more diluted in HCL (1:1).The potassium content was determined with the use of a spectrophotometer Sherwood 420. During the measurements the international standard “Cordoba-muscovite” was used to test the procedure. The analytical error was 0.02% K2O. 3. Ar determination The isotopic composition of Ar was determined by the extraction method (Bonhomme et al., 1975) using an MS 20 mass spectrometer. The sample was fused in a Ti-Ta crucible resistance heating (Durakiewicz,1995) and the released gas was purified on Ti and Or-Al Getters. The analytical precision was controlled by the measurements of the radiogenic 40 Ar content of the international standard GLO before the samples were measured. The mean content of four determinations made previously, the analysis was (24.99 +/- 0.48 (2Θ)) x 10 exp – 6 cm exp3/g STP being well in the range of the accepted values: (24.85 +/- 0.50) (Odin et al., 1982). The overall precision of the K-Ar age determinations which were calculated using the decay constant recommended by Steiger and Jaeger (1977) was better than 2%. 4. Results The results of the measurements are presented in the table. Name

Weight (mg)

% 4040Ar

40Ar 40 (pmol/g)

Age Ma

Error Ma

Sample A

55.50

6.77

38.9

89.3

7.6

0.3

Sample B

48.12

6.70

34.7

90.2

7.7

0.3

Sample C

52.16

6.63

34.3

86.5

7.5

0.3

5. Limitations of interpretation All results show that the material prepared for measurements fulfill the criteria postulated by Odin, et al. (1982). Content of potassium was determined by 50 mg, while the normal weight of samples is about 100 mg. This was due to the small dimensions of the source samples. Interpretation of the results has one limitation: The K-Ar method cannot determine whether the glauconite has been redeposited.

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Special Issue, No. 5

The Wadi Al Farigh Member of the Sahabi Formation MUFTAH SHAWAIHDI and TAOUFIG AL TRABELCI

ABSTRACT There is significant cross-bedding of sediments in the Miocene Wadi Al Farigh Member of the Sahabi Formation, Libya. The member consists of lime-sand shoal facies, oolites, and calcarenites alternating with green calcareous siltstone, silty clay, sandy marl, and dolomitised marls. Crossbedding structures are seen in limestone facies dominated by calcarenites and oolites. The Wadi Al Farigh Member in the study area constitutes a barrier bar facies separating the northern coastal environment from the inland southern basin and would have acted as an epeiric sea shelf that restricted the deposition of sabkhas and lagoons. Current flow oscillated between northwest to southeast. Sediments deposited landwards through the lime-sand migration built up a sand-body bar which is characterised by features such as inlets, flood, ebb, and dominant tidal current flows, and washover deposits. Many sedimentary structures have directional or at least orientation properties. These structures serve as a basis for palaeocurrent determinations. The use of cross-bedding continues to be the most useful and widely studied of all palaeocurrent structures so that field studies now suggest that a cross-bedding map pattern has environmental significance. This study represents work dealing with cross-bedding as a means of palaeocurrent analysis of the Wadi Al Farigh Member of the Sahabi Formation, Libya. The Wadi Al Farigh Member is of Miocene age (Giglia, 1984). It consists of lime-sand shoal facies, oolites and calcarenites alternating with green calcareous siltstone, silty clay, sandy marl and dolomitised marls as calcareous lithotypes. Cross-bedding structures seen in limestone facies are dominated by calcarenites and oolites.

Muftah Shawaihdi, Department of Earth Sciences, University of Garyounis, Benghazi, Libya, shawaihdi@yahoo.com Taoufig Al Trabelci, Geologist, General Water Authority, P.O. Box 2845, Benghazi, Libya, taoufig@yahoo.com

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The Wadi Al Farigh Member in the study area constitutes a barrier bar facies separating the northern coastal environment from the inland southern basin (Giglia,

1984). The back barrier area is a restricted lagoonal facies of sabkhas, as Sabkha Al Hamra and Sabkha Al Qunayyin. The sedimentological packages of the study area

Figure 1. Location map of study area. Ajdabiya sheet, Geological Map of Libya. Studied Stations 1-9 72

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Figure 2. View of the escarpment of Wadi Al Farigh Member exposed along Wadi Al Farigh

METHOD OF STUDY

consist of peloidal facies, oomicrite, and oosparite facies, alternating with restricted deposits of siltstone as seen in some stations. The cross-bedding in the study area is informative as to the directional range, patterns, and types of cross-bedding.

The area of study was subdivided into nine stations distributed along the outcrops exposed in Wadi Al Farigh. Each station was studied separately by taking samples, measuring cross-bedding direction readings, dips, and strikes, general descriptions of the outcrops, taking photographs, and drawing sketches. The Geologic Map of Libya "Ajdabiya Sheet" (Giglia, 1984) has been used in this work. Collected cross-bedding data were analysed by rose diagrams for each crossbedded lithology, for each station, and as a composite rose diagram for all stations. The samples were thin-sectioned and studied microscopically by identifying the rock texture. The cross-bedding readings were analysed by using a computer program to

LOCATION The study area is located about 221 km southwest of Benghazi and about 61 km southesast of Ajdabiya. It is bordered by coordinates 20째30'00" and 20째46'00" E longitude and 30째24'42" and 30째31'00" N latitude. The Wadi Al Farigh Member is exposed along a dominant northeastsouthwest direction in an area about 16 km long and about 1 km wide along Wadi Al Farigh (Figures 1 and 2) .

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calculate statistically the mean vectors showing the effective direction of the current.

REGIONAL GEOLOGY Southeast of Ajdabiya the exposed sedimentary rocks range in age from Middle Miocene to Quaternary (Figure 3). They have been grouped into four sedimentary cycles separated by unconformities between them. These units are as follows; Middle Miocene Msus Member of Ar Rajmah Formation, Late Miocene Sahabi Formation, the PlioPleistocene Qarat Weddah Formation, and the Pleistocene-Holocene Ajdabiya and Gargaresh Formations (Giglia, 1984).

PREVIOUS WORK In the early thirties most of the geological literature concerning the Ajdabiya area was devoted to the Sahabi outcrops by Italian authors Desio (1928b, 1931, 1932, 1935b), Stefanini (1934a, 1934b, 1935), and Marchetti (1934). They attributed these deposits to a Lower Miocene "Sahabi Series." Other work on the vertebrate faunas from As Sahabi by Italian palaeontologists D'Erasmo (1951, 1954), Maccagno (1951) and Leonardi (1954) allowed the upper part of sequence to be assigned to the Pliocene age. Successive works by Maglio (1970) and Savage (1971, 1974) confirmed a PlioPleistocene age for the same deposits. In more recent years, an international program has been established with very detailed palaeontological and stratigraphical research in the Sahabi area. The result of this framework program was published by Boaz, Gaziry, and El-Arnauti (1979) and de Heinzelin, El-Arnauti, and Gaziry (1981). The investigation details of the Sahabi Series led to identifying new lithostratigraphic units and attributed the age varying from 7 to 4 ma (Upper Turolian to Ruscinian) in terms of European mammalian faunas. Magnier in 1964 reconstructed a Late Tertiary succession in the Gulf of Sirt, and correlated the Wadi Al Farigh oolitic bar with the Qasr As Sahabi outcrops. Giglia (1984) edited the Geological Map of Libya, "Ajdabiya Sheet" at a scale 1:250,000, and this stratigraphic division is used in this study.

LATE MIOCENE Sahabi Formation The Sahabi Formation represents a transgressive pulse, comprising a temporary retreat of the sea in Late Serravallian-Early Tortonian times, and general regression in the Late Messinian (Barr and Walker, 1973; Megerisi and Mamgain, 1979). This formation includes shallow marine to littoral and lagoonal facies with large evaporitic and coastal-bar episodes, mainly represented by the sandy limestone, silty clays, calcareous sandstone, calcarenites, and selenitic gypsum. It was studied in great detail and subdivided into three new members by Giglia (1984). These members are from bottom to top as follows. Sabkha Al Hamra Member The Sabkha Al Hamra Member consists of littoral, shallow marine and evaporitic sediments with considerable fine terrigenous supply. This member includes two facies. The transgressive facies is the

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Figure 3. Stratigraphic sequence of the overall region of Ajdabiya town and adjoining areas according to Giglia (1984)

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lower part and is dominantly formed by sandy limestone, calcareous to calcarenaceous sandstone, with intervals of siltstone, silty clay to claystone, sand and sandy calcarenite. Gypsum occurs as both small selenitic crystals and as diagenetic replacement of rocks and fossils. The regressive upper facies is dominantly composed of sand, green clay, clay, silt, and siltstone, with some intervals of sandy limestones, coral sandstone, calcarenaceous and calcareous siltstone, and some selenitic gypsum at various levels.

higher energy marine facies of calcarenite. This member rests paraconformably on top of the Sabkha Al Hamra Member and it is overlain by the Wadi Al Farigh Member. Wadi Al Farigh Member The name originates from the Wadi Al Farigh area. This member is formed by washed calcarenite and oolitic limestone forming high-energy lime-sand shoal and bar deposits (Figures 2 and 4) crossing in a dominant northeast-southwest direction. The Wadi Al Farigh Member is heteropic with the Sabkha Al Qunayyin Member. The heteropic relationship with this member can be only supposed on the basis of palaeogeographic reconstruction since the contact is never exposed. The Wadi Al Farigh Member corresponds to the Wadi Al Farigh Limestone of Magnier (1964). The

Sabkha Al Qunayyin Member This member is formed by low to moderate energy, shallow marine to lagoonal protected facies of sandy limestone, clay, sandstone, and silty sand. These pass northwards from moderate to

Figure 4. Far point of station 3 represented by low outcrops

Special Issue, 2008

type locality of this member is quite uniform, with mainly oosparites and calcarenite often cross-bedded with minor interbeds of green calcareous siltstone, silty clays, sandy marls, and dolomitised marls (Figure 5). The faunal content from macroand micropalaeontological evidence indicates superposition on the late Tortonian-Early Messinian Sabkha Al Hamra Member, and a heteropic relationship with the Messinian Sabkha Al Qunayyin Member. Local and regional palaeogeographic relationships lead us to assume a Messinian age for the Wadi Al Farigh Member.

WADI AL FARIGH MEMBER SAHABI FORMATION

Figure 5. View of outcrop in station 3 showing large scale cross-stratification overlying interlaminated green shale and white calcareous siltstone (rhythmites).

Sedimentology and Palaeocurrent Analysis of the Wadi Al Farigh Member The lithologies as well as the sedimentary structures in each station of the study area have been investigated separately, which led to a subdivision of the sequence into calcarenites, oolites and siltstone facies. The calcarenite facies (Figure 6) is composed of biopelsparites, packstone of peloidal fine to medium grains. Grains are subrounded to rounded, moderate sphericity, well-sorted, grainsupported, biomoldic porosity in parts (Figure 7), and planer and trough crossbedding in many parts. The oolitic facies is composed of oosparite, grainstone, packed oobiomicritic (rudstone) and oopelmicrite in some parts. The sediments are fine to medium-grained, rounded, and well-sorted. There is high sphericity and grainsupported, vuggy, intergranular, and biomoldic porosity. The sediments are very highly cross-bedded.

Figure 6. Photomicrograph of the calcarenitic facies

Figure 7. Photomicrograph of the peloidal facies with bimoldic porosity

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GENERAL DESCRIPTION The cross-bedding of the study area is characterised by an abundance of planar as at station 8 (Figure 8) and herringbone types, with varying scales of plunging angles, lengths and widths of sets. The palaeocurrent pattern is strongly bimodal as seen in stations 4, 6, and 7 (Figure 9). Current flow oscillated between northwest to southeast. The major current was coming from a northwest direction with a smaller effect from the other side. Station 9 represents a unimodal type of crossbedding. In station 9 the unimodal palaeocurrent pattern of northeast direction shows a southwest current flow (Figure 10). In Figure 11 the rose diagrams represent the polymodal pattern of palaeocurrent trends. The southeast effective trends indicate a predominant northwest flood current flow (Figure 11). In the nine stations along the wadi, the major rose diagrams indicate the same effect of polymodal northwest flood current flow, with vector means calculated by computer program. A general scheme of the sediments (Figure 12) illustrates the direction of flooding and ebbing currents and the flow out of the wadi.

Figure 8. Close-up of outcrop at station 8 showing planar, large-angle cross-bedding

Figure 9. Surface exposure showing herringbone cross-bedded structure at station 4

RESULTS AND ENVIRONMENT INTERPRETATION In general the Sahabi Formation is the product of a series of minor marine transgressive and regressive cycles. The presence of an oolitic bar is required to explain the existence of the low-energy deposits in the Sahabi Formation (Giglia, 1984). The evolution of the oolitic bar of the Wadi Al Farigh Member would have completely isolated the open shelf from the inner basin (Figure 13). It would have acted as an epeiric sea shelf that restricted the

Figure 10. View of outcrop of station 9 showing large-scale planar cross-bedding, looking southeast

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deposition of sabkhas and lagoons. As far as the sediments deposited landwards through lime-sand migration, the buildup of the bar is characterised by features such as inlets, flood- and ebb-current flow features, and washover deposits. The dominant tidal current of high energy consisted

of mobile shoal water with some restriction and immobility. The question in the study area was the origin and direction of the tidal current. The answer provided by the rose diagrams of the cross-bedding (Figure 11) indicated that the currents flowed from the northwest the majority of the

Figure 11. Location map of the stations and their palaeocurrent directions in the study area. Wadi Al Farigh, about 61 km southeast of Ajdabiya

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Figure 12. Composite lithologic columnar section of studied stations showing the palaeocurrent trends, sedimentary structures, and depositional environments.

time. A minority ebb-tidal current flow from the southeast occurred through the inlets (see Figure 13). The herringbone structure is

indicative of oscillation of flood- and ebb-tidal current flows through the inlets. There is generally a bimodal pattern of current flow seen.

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Figure 13. General scheme showing the tidal palaeocurrent direction in the Wadi Al Farigh study area

During periods of agitation of mobile shoal water, indicated by the crossbedded lithologies, one may estimate that the water depth ranged from 60cm to 1m. This is in contrast to immobile shoal water seen in some lithologies in which the restriction of water flow yields an absence of structure, usually horizontal stratification or massive bedding. On the other hand, channel bottom deposits preserve some periods of channel activity as represented by the orientation of fossils.

Sea Drilling Project, Initial Report Vol. 13 (eds W. B. F. Ryan, K.S. Hsu, et al. Washington, 1244-1251. BOAZ, N. T., GAZIRY, A. W., and EL ARNAUTI, A. (1979). New fossil finds from the Libyan Upper Neogene site of Sahabi. Nature 280, 137-140. D'ERASMO, G. (1951). Paleontologia di Sahabi (Cirenaica). I Pesi di Sahabi. Rend. Accad. Naz. del XL, Ser. 4, 3, 33-69. D'ERASMO, G. (1954). Paleontologia di Sahabi (Cirenaica). Sopra un molare di Teleoceras del giacimento fossilifero di Sahabi in Cirenaica. Rend. Accad. Naz. del XL, Ser. 4, 4-5, 89-102.

REFERENCES BARR, F. T. and WALKER, B. R. (1973). Late Tertiary channels system in Northern Libya and its implications on Mediterranean Sea level changes, In: Deep

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DESIO, A. (1928b). Sulla presenza del Miocene nella Sirtica (Libia). Atti R. Accad. Naz. Lincei, Ser. 6a, 8, 516-518.

MAGNIER, P. (1964). Le Neogene du bassin de Syrte et du sud de la Cyrenaique (Libye). Inst. "Lucas Mallada" C.S.I.C., Cursillosy conferecias, Madrid IX, 193-198.

DESIO, A. (1931) Osservazioni geologiche e geografiche compiute durante un viaggio nella Sirteica. Boll. R. Soc. Geograficha Ital., Ser. 6a 8(4), 275-299.

MARCHETTI, M. (1934a). Itinerari geologici in Cirenaica, Atti Sec. Cgr. Seudi Colonial, Napoli, 273-286.

DESIO, A. (1932). Nuovi dati sulla geologia della Libia. Mem. Geol. e geogr. di G. Dainelli 3, 205-227.

MARCHETTI, M. (1934b). Note illustrative per un abbozzo di carta geologica della Cirenaica. Boll. Soc. Geol. Ital. LIII (2), 309-325.

DESIO, A. (1935b). Appunti geologici sui dintorni di Sahabi (Sirtica). Rend. R. Ist. Lombardo Sci. e Lett., Ser. 2a, 68, 137-144.

MEGERISI, M. F. and MAMGAIN, V. D. (1979). The Neogene of Libya and its evaporites, A preliminary survey. 7th Int. Congress on Mediterranean Neogene, Athens. Ann. Geol. Pays Hellen. 1979, 789798.

GIGLIA, G. (1984). Geological Map of Libya 1:250,000. Sheet NH 34-6, Ajdabiya Explanatory Booklet. Ind. Res. Cent., Tripoli, 93 p.

SAVAGE, R. J. G. (1971). Review of the fossil mammals of Libya. Symp. Geol. of Libya, Fac. Sci., Univ. Libya, Tripoli, 215226

DE HEINZELIN , J., EL ARNAUTI, A., and GAZIRY, A.W. (1981). A preliminary revision of the Sahabi Formation 2nd Symp. on Geol. of Libya, Al Fateh Univ., Tripoli. 127-133. LEONARDI, P. (1954). Paleontologia di Sahabi (Cirenaica). I suidi di Sahabi nella Sirtica (Africa Sett.) Rend. Acc. Naz. dei XL, Ser. 4, 4-5, 57-88.

SAVAGE, R. J. G. (1974). Meotian/Pontian of Egypt and Libya. Mem. du B. R. G. M., Paris 1 (78), 239-240. STEFANINI, G. (1934a). Sulla scoperta di resti fossils di Vertebrati della Sirtica. Boll. Geogr. 5-6, 152-177.

MACCAGNO, A. M. (1951). Paleontologia di Sahabi, Cirenaica. I coccodrilli di Sahabi. Rend. Acc. Naz. dei XL, Ser. 4, 3, 71-177.

STEFANINI, G. (1934b). Giacimento miocenico a Vertebrati nella Sirtica. Atti Soc. Toscana Sci. Nat., Pisa 54, 27-28.

MAGLIO, W. J. (1970). Early Elephantidae of Africa and tentative correlation of African Plio-Pleistocene deposits. Nature 225, 328-332.

STEFANINI, G. (1935). Breve guida alle escursioni geologiche in Cirenaica. Boll. Soc. Geol. Ital. 54, 1-117.

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TUCKER, M. E. (1981). Sedimentary Petrology. An Introduction. London, 3, 3940, 97-102. WALKER, G. R. (1984). Facies Models. London, Ainsworth Press, 130-131.

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Special Issue, No 5

Tracing the As Sahabi Channel System in the Ajdabiya Trough, Central Sirt Basin, Libya

CARLO NICOLAI

ABSTRACT The As Sahabi Channel System is a major geological feature buried in the subsurface of the Ajdabiya trough following the central axis of Sirt Basin. The channel system was developed as a result of the Mediterranean salinity crisis during the Messinian. Utilizing modern geophysical techniques, such as 2D and 3D seismic and aeromagnetic data it has been possible to trace the path of the Channel System along the last 200km of its course on land from the Qasr As Sahabi area to Marsa Al Brega on the coast. The channel width is over 5km, getting wider northwards towards the present-day coastline. Its base deepens 250m in the studied tract with an apparent gradient of some 1.25m/km. Other features such as embayments and tributaries have also been identified.

Carlo Nicolai, Shell E &P Libya GmbH, Abunawas 2, Gargaresh Rd 6.2km, P.O. Box 91791, Tripoli, Libya, C.Nicolai@shell.com

ÂŠ Shell Exploration and Production Libya GmbH [2008]

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targets Shell is pursuing in this area, the Sahabi channel system incision was always evident in the final seismic image. When airborne magnetic data was acquired, high frequency-low amplitude magnetic anomalies were observed. These also turned out to correlate very well with the Messinian channel systems.

INTRODUCTION The As Sahabi channel system has been known to oil companies operating in the Sirt basin for over 40 years (Barr and Walker, 1973), mainly as a nuisance for seismic data quality. These buried channels have an erosional and very rough base and are filled by relatively slow velocity sediments; the seismic beneath shows poorly imaged and very noisy data, posing oil explorationists with unwelcome challenges during seismic data processing and interpretation. The system downcuts deeply into Miocene sediments in response to changes in the erosion base level, resulting from the Mediterranean sea level lowering that took place during the Messinian salinity crisis. This paper attempts to trace the buried course of the channel system over the last 200 km from the Qasr As Sahabi area to the present day coast line at the town of Marsa Al Brega using geophysical exploration methods currently in use at Shell.

Seismic Acquisition and Processing During the seismic data acquisition campaign (2005-2007) in the Sirt basin a coarse grid of 2D seismic lines (some 10000km) and a number of 3D surveys were acquired. Since Shell pursues deep gas opportunities in this area, the acquisition parameters were optimized for imaging deep targets. The 2D was acquired using a symmetrical 480 channel split spread, with 25m receiver-group spacing, 6km maximum offset, and a vibroseis shot interval of 25m. Nominal fold is 240. Obviously these 2D acquisition parameters are also well suited to image shallow structures like the Sahabi channel. 3D data was acquired using an efficient symmetric swath geometry consisting of 8 parallel receiver lines, 500m apart, with 240 live receivers each, and a 50m receiver-group spacing. Vibroseis shots were fired between the two central receiver lines in a zigzag pattern, whereby the in-line and cross-line move-up is 50m between shots. A complete zigzag comprises 20 shots spread out over 1km inline move-up. Either two or four zigzags with 200m separation were used, giving a shot density of either 80 or 160 shots/km2 and a nominal fold of either 96 or 192, respectively. Maximum in-line offset is 6km, maximum cross-line offset is 2km,

DATA AND METHODS As a result of the recent NOC-Shell agreement, Shell was awarded exploration rights in five blocks, covering some 20000 km2 located mainly in the northern Ajdabiya trough, between the coastline and the general area of the Amal field in the centre of the Sirt basin (Figure 1). As part of the exploration activities an extensive geophysical program is being carried out. The program includes 2D and 3D seismic as well as high-resolution aeromagnetic coverage of the concession area. Although the geophysical data acquisition and processing program was designed to illuminate the deep exploration

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TRACING As SAHABI CHANNEL

Figure 1. Basemap. Shell acreage in light color. 3D surveys area represented by thick black borders.

and natural square bin size is 25m. This rather wide and sparse geometry is well suited and very efficient for deep exploration targets, but it results in poor sampling of the shallow (0-1000ms twt) subsurface. Although the details of the As Sahabi channel are poorly imaged by the 3D data there is still great benefit in the fact that there is complete coverage as opposed to the coarse grid of 2D lines.

Interpretation The base of the channel was picked on the 2D and 3D seismic datasets. The quality of the pick is variable, generally poor to fair but sometimes the seismic character of the erosional cut is very good. The shoulders of the channel were tentatively picked but in this case the pick is poor and the depth map only indicative. To date, the interpretation has not been calibrated to outcrop geology. Moreover,

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any tie to existing wells is made difficult by the lack of data in the very shallow section, in fact exploration wells are seldom logged or sampled in the Plio-Miocene interval. The 2D seismic line spacing is quite large (2 to 5km) resulting in some uncertainty with the tie from line to line. An attempt to pick some reflectors within the channel fill was also made but the results cannot be extended consistently for more than a few lines. The final map was depth-converted using an average of velocity of 1900m/sec. The map shows the current geometry of this area, being not corrected for any post-

Messinian tectonic movement such as tilts and/or inversions. The values on the map have to be considered as current depth below sea level. Magnetic After careful processing of the magnetic data, a shaded relief image of the 1st vertical derivative magnetic data reveals the shape of the channel system (Figure 2). The location of these magnetic anomalies correlates very well with the channel systems visible on seismic data. The highresolution aeromagnetic data allows

Figure 2 - Shaded relief image of the High resolution aeromagnetic data (1st vertical derivative). 88

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improved mapping of the channel systems in areas of sparse seismic data. The amplitude of the magnetic anomalies has been calibrated with seismic lines, pointing to a magnetic susceptibility contrast of 20 to 50 microcgs between the channel fill and the adjacent sediments. The channel fill appears to be associated with a higher magnetic susceptibility, indicating a larger amount of magnetic content present in the channel.

between 5 and 6 km, getting wider northwards towards the present-day coastline. The channel is about 550 meters deep in the As Sahabi area and attains up to 750 meters near Marsa Al Brega (Figures 3 and 4). The calculated average gradient of this tract is about 1.25 m/km, a gradient that is correlatable to that of major gorges such as the Grand Canyon in the USA, which ranges from 0.7 to 2.5 m/km (Benke and Cushing, 2005). The above gradient reflects the current geometry of the canyon and still needs to be corrected for any postMessinian tectonic effect. The canyon is also of similar dimensions to the channel cut by the Nile in Egypt during the Messinian event, being 570m below sea level at Cairo (El-Arnauti et al., 2004).

DISCUSSION OF THE RESULTS The As Sahabi canyon has been mapped for about 200km from just north of the Amal field to the current coastline. In the study area the channel width ranges

Figure 3. Depth map of the base of the Sahabi Channel. Blue colors indicate deep; brown colors shallow. 89

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Although the seismic resolution is not high enough to detail the internal structures of the channel infill, it is possible to identify some of the channel systemâ&#x20AC;&#x2122;s major physiographic elements. Integration of all geophysical data meanwhile strongly suggests that the channel systemâ&#x20AC;&#x2122;s trend follows some deeper structural grain in the Ajdabiya trough. The southernmost segment of the channel runs in an ENEWSW direction then turns to the northwest in the vicinity of well D1-6. From this point on the Sahabi channel maintains a NW direction as it crosses the present-day shoreline towards the continental shelf. In fact the seismic data demonstrate that the NW-SE trending branch of the channel system is split into three segments

connected by SW-NE tracts. The 3D seismic data set also shows faults associated with one of these channel bends (Figure 5B). Therefore, it is postulated that the geometry of the channel system is structurally controlled by the associated geometry of the eastern flank of the Jahama platform. The NW-SE segment of the channel is sometimes asymmetric in cross section, with the more incised part being to the West against the Jahama platform. Its base appears here to be controlled by a number of small listric faults (Figure 5A). This area represents the hinge between the Ajdabiya Trough and the Jahama Platform. This structural boundary is the site of mechanical weakness and demonstrates evidence of

Figure 4. 3D View from the SE of the canyon. Note the current coastline of the Sirt basin as reference. Vertical lines represent exploration wells.

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Figure 5. Evidence of tectonic control; 5A Shows how the western flank of the channel is controlled by listric faults whilst in 5B (time slice at ca 800 ms twt) some WSW-ENE faults lead the channel to a 90deg turn westwards.

differential compaction of the MioOligocene section, which shows dramatic thickening in the Ajdabya trough as compared to the Jahama Platform area. Imaging data shows the main channel system was fed laterally by sets of short, perpendicular, sinuous tributaries that measure up to 10km in length (Figure 6). One of these tributaries feeds into a large embayment developed on the eastern bank of the channel, at approx 3310000m Northing (Figure 7). The fill of this bay shows characters of terracing. From this latitude onward, the channel widens and loses its deep, incised

canyon characteristics found to the south. These geometric changes may suggest a transition into a more marine environment. Whilst the canyonâ&#x20AC;&#x2122;s western bank and the deepest incision maintain a NW-SE direction, the eastern bank turns to the ENE to form an escarpment some 20-30 km to the south to the current coast line (Figure 8). It is possible that such an escarpment represents the early Messinian pre-salinity crisis coastline, remodelled by erosion during the drying up of the Mediterranean. Its morphology shows a series of short perpendicular incisions, much wider than the ones feeding the channel in the southern

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Figure 6. Time slice at ca 400 ms twt showing one of the major short tributaries.

Figure 7. Embayment on the eastern rim of the channel. Interpreted and Uninterpreted seismic line (7A); The time slice (7B) shows the areal extension of the bay and its tributary.

Figure 8. The time slice (8B) shows a detail of a high cliff. The subsequent filling is characterized by very well organised packages (8A).

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of the indirect techniques we have utilised and the quality of the data it has been possible to identify a number of other features such as embayments, tributaries, and the Messinian palaeo-coastline. Detailed studies of the channel filling are not possible with the current data, however if required the technology is available. High-resolution seismic with penetration of a few hundreds of meters is routinely used to study shallow features also in desert areas (e.g. Haberland, 2007). Given its magnetic character, detailed analysis of the channel fill minerals in comparison with the surrounding material would be required to further distinguish the causes for the magnetic signature of the As Sahabi channel system and its provenance. High-resolution aeromagnetic data can be used to determine the location and width of channel systems if these are associated with a sufficient magnetic susceptibility contrast relative to their respective depth. If the magnetic susceptibility contrast is known from correlation with seismic data or magnetic susceptibility measurements, it is possible to use the magnetic data to model the relief of such channel systems.

sector, entering the Mediterranean basin. The channel sediment infill is generally poorly organized in the south, though locally it is possible to pick more phases of filling with erosions in between. Internal organisation of sediments improves towards the coastline. Sediments are stacked in a number of packages with clear internal structures such as foresets that have transition-to-marine, shore and estuarine characteristics (Figure 8A). As already indicated, the channel sediment infill attains positive magnetic properties. A small concentration of magnetite in the sediment can produce an observable magnetic anomaly. The magnetic anomalies associated with channel fills may have several causes (Gunn, 1997), such as disseminated pyrrhotite in shale or ilmenite that may also give a weak magnetic response. Another cause could be maghemite (a weathering product with a similar susceptibility to magnetite and which is extremely stable under oxidising conditions) that is often preserved in channels. A likely source of magnetic minerals is the erosion of intrusive and/or volcanic sequences, suggesting that the channel might have cut across an igneous hinterland.

ACKNOWLEDGEMENTS I would like to thank Rian de Jong for his input on seismic processing and Susanne Witte who contributed with the analysis of the magnetic data. Bashir ElMejrab. Ahmed El-Hawat and Helena Griffiths reviewed the manuscript and offered valuable suggestions. Finally, thanks to Mahmud M. Ismail, NOC, and Shell E&P Libya who have granted permission to publish this paper.

SUMMARY AND CONCLUSIONS The last 200km of the Sahabi Channel system path has been reconstructed using geophysical data. Some of the characteristics described for other locations in the existing literature, such as a width of over 5km and depths of more than 500m, are confirmed. Keeping in mind the limits

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REFERENCES MCCAULEY, J.F., SCHABER, G.G., BREED, C.S., GROLIER, M.J., HAYNES, C.V., ISSAWI, B., ELACHI, C., and BLOM, R (1982). Subsurface valleys and geoarchaeology of the eastern Sahara revealed by shuttle radar. Science 218, 1004-1020.

BARR, F.T. and WALKER B.R. (1973). Late Tertiary channel system in northern Libya and its implication on Mediterranean sea level changes. Initial Report Deep Sea Drilling Project, Leg 13, 1244-1251. BENKE, A.C., and CUSHING C.E. (2005). Rivers of North America. Amsterdam, Elsevier.

MCCAULEY, J.F., BREED, C.S., SCHABER, G.G., MCHUGH, W.P., ISSAWI, B., HAYNES, C.V, GROLIER, M.J., and KILANI, A.E. (1986). Paleodrainages of the eastern Sahara - The radar rivers revisited (SIR-A/ B implications for a mid-Tertiary transAfrican drainage system). IEEE Transactions on Geoscience and Remote Sensing GE-24, 624-648.

EL-ARNAUTI A,, and EL-SOGHER A, (2004). Short Notes and Guidebook on the Geology of the Qsar As Sahabi Area. Sedimentary Basins of Libya, 3rd Symposium Fieldtrip. Tripoli, Earth Science Society of Libya. GRIFFIN, D.L. (2006). Late Neogene Sahabi rivers of the Sahara and their climatic and environmental implications for the Chad Basin. Journal of the Geological Society 163, 905-921. GRIFFIN, D.L. (2002). Aridity and humidity: Two aspects of the late Miocene climate of North Afri ca. Palaeogeography, Palaeoclimatology, Palaeoecology 182, 6591. GUNN, P.J. (1997). Application of aeromagnetic surveys to sedimentary basin studies. AGSO Journal of Australian Geology and Geophysics 17 (2), 133-144. HABERLAND, C., MAERCKLIN, N., KESTEN, D., RYBERG, T., JANSSEN, C., AGNON, A., WEBER, M., SCHULZE, A., QABBANI, I., and EL-KELANI, R. (2007). Shallow architecture of the Wadi Araba fault (Dead Sea Transform) from high-resolution seismic investigations. Tectonophysics 432, 37â&#x20AC;&#x201C;50.

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The Development, Decline and Demise of the As Sahabi River System over the Last Seven Million Years N.A. DRAKE, A.S. EL-HAWAT, and M.J. SALEM

ABSTRACT Data on the present day topography, geomorphology and geology were used to establish a chronology for the development and demise of the As Sahabi River system. Although the origin of the river system is shrouded in mystery, it is clear that by the Late Miocene Libya was dominated by two large rivers systems that flowed into the Mediterranean Sea. The As Sahabi River in the Sirt Basin was draining central and eastern Libya, whereas the Wadi Nashu River in the Murzuq Basin was draining much of western Libya. In the early Messinian the Nashu River was blocked due to crustal thermal uplift of the Al Haruj area that preceded volcanic activities. The drastic fall in the riverine base level associated with the Messinian desiccation of the Mediterranean Sea promoted downcutting and extension of the Sahabi River system and its tributaries. However, the now blocked Nashu River could no longer respond to this event allowing the As Sahabi river to capture much of its catchment in Murzuq basin. The subsequent Early Pliocene sea level rise led to the infill of much of the As Sahabi River system in northern Libya by marine and fluvio-estuarine sediments. As this was occurring volcanic activities and thermal uplift in the eastern Tibisti region deprived the As Sahabi River of its headwaters in Chad, while associated subsidence in the Al Kufrah Basin led to extensive lacustrine development and caused expansion of the Al Kufrah River system at the expense of the Sahabi River. By the Late Pleistocene the Al Kufrah River dominated the palaeohydrology of eastern Libya at the expense of the Sahabi. However, in western Libya apart form the Wadi Barjuj which was blocked by volcanic activity some time between 4 and 2 ma, the Serir Tibisti tributaries of the As Sahabi River remained largely unaffected by these processes. This event augmented the closed basin in the Fazzan where a giant lake developed during humid periods. Overspill of this lake may have periodically connected it to the As Sahabi system. Though the As Sahabi River was periodically active during the Late Pleistocene and Holocene, little change occurred during this time because a reduction in water availability led to a decline in fluvial activity.

N.A. Drake, Department of Geography, Kings College, London, WC2R 2LS, United Kingdom, nick.drake@kcl.ac.uk A.S. El-Hawat, Earth Sciences Department and the Research Centre, University of Garyounis, P.O.Box 1308, Benghazi, Libya, ashawat@ltt.net M.J. Salem, Earth Sciences Department, Al-Fateh University, P.O. Box 13355, Tripoli, Libya, m.j.salem@lycos.com

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imagery provided further information on palaeo-river systems providing information on fluvial deposits with little or no topographic expression as well as providing information on sedimentary bedforms and sometimes indicating compositional differences between sediments.

INTRODUCTION The palaeohydrology of the As Sahabi River system is poorly understood in terms of the sequence of geological events that led to its formation and subsequent demise. This paper aims to further our understanding of these issues by considering geological and geomorphological events throughout Libya since the Late Miocene.

RESULTS Late Miocene and Messinian

METHODS

The hydrological system in Libya during the Miocene that ultimately gave rise to the As Sahabi River system is poorly understood. Surface and subsurface geological evidence suggests that in eastern and central Libya the As Sahabi Riverâ&#x20AC;&#x2122;s path was controlled by the inherited NNW-SSE trending structural axis of Ajdabiya trough at the centre of Sirt basin. Remote sensing data suggest that the main channel of the As Sahabi River system in this region was fed by branches issuing from the Tibisti Mountains and the Al Kufrah basin to the south (Figure 1). Another substantial river channel that we call Wadi Nashu drained western Libya at this time. It originated in the mountains surrounding the Fazzan basin and terminated on the north-east margin of the Gulf of Sirt (Drake, et al., submitted; Figure 1). The Sahara is thought to have been predominantly humid during the Late Miocene and thus these rivers may well have been active for much of the time (de Menocal, 2004). At the end of the Miocene, Wadi Nashu appears to have been blocked by the initiation of thermal uplift and volcanism

To further our understanding of the palaeohydrology of the As Sahabi River system we have produced an integrated interpretation of the 90m Shuttle Radar Topography Mission (SRTM3) digital elevation model (DEM), Landsat Thematic Mapper (TM) satellite imagery, geological maps and the wider geological literature in order to provide an integrated understanding of the geology and geomorphology of the region. Particular attention was paid to the literature on the ages of the different volcanoes in Libya (e.g. Busrewil and Wadsworth, 1980; Peregi, 2003) as they appear to exert a large control on the palaeohydrology of the river system, a relationship that was previously unrecognised. The SRTM DEM was used to identify palaeo-river channels. The geomorphology of the river channels was interpreted to identify specific events, such as river capture and the blocking of river systems by the development of volcanoes within their course. Interpretation of Landsat TM false colour composite (FCC)

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Fig.ure 1. Map showing the probable river systems found in Libya during humid periods in the late Miocene before Wadi ash Shatti, Wadi al Hayat and Wadi

at Al Haruj al Aswad and its subsequent growth towards Jabal As Sawda (Ade-Hall et al., 1974; Peregi, 2003). The truncation of Wadi Nashu river led to the development of a closed basin in the northern half of the Fazzan within which a lake would have developed during humid periods (Figure 2).

The end of the Miocene also saw the closure of the Straits of Gibraltar by tectonic activity in Africa and Europe which led to the Mediterranean Messinian salinity crisis in the late Messinian period (~5.9 ma). The climate in the Mediterranean region and North Africa at

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Figure 2. Map showing the probable river and lake systems during humid periods in the Messinian once the Nashu River system had been blocked by Al Haruj al Aswad volcano and the Mediterranean Sea had dried up. Note the extension of the river systems

this time appears to have been arid and thus with no input of water from the Atlantic Ocean the Mediterranean Sea gradually dried up (Hs端 et al, 1977). This caused a drastic fall in the base level of the rivers because much of the Mediterranean

is 3km below sea level and in some places it reaches nearly 5 km. This drop in base level caused down-cutting and extension of river systems during subsequent humid periods. There is sedimentological and isotopic evidence that such humid episodes 98

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of lines of enquiry. Firstly, there is geomorphological evidence for a lake outflow channel from palaeolake Megachad towards the As Sahabi River (Griffin, 2006; Griffin, 2002); secondly, a fossil fish and other aquatic species has been found in the As Sahabi River deposits that is thought to have originated in the Niger River (Boaz et al., 1986), and presumably got to the As Sahabi River via this Lake Megachad connection; and finally fossils of similar semiaquatic anthracotheres are found in both the Sahabi River and Lake Megachad deposits (Lihoreau et al., 2006; Pavlakis and Boaz, this volume). This was probably the most important event in the evolution of the As Sahabi River as it could have more than doubled the size of the As Sahabi River’s catchment by adding the ~2.5 million km2 of the Chad catchment to the ~1.5 million km2 of the As Sahabi River catchment. Thus by the end of the Messinian it appears that the Mediterranean continental margin was fed through the Gulf of Sirt by a very large river system with deeply cut canyons that drained much of Libya and Chad as well as parts of Niger, Nigeria, and Algeria.

occurred during the Late Messinian as the refilling of the Mediterranean at this time was not simply due to seawater influx from the Atlantic Ocean at the Straits of Gibraltar as was initially proposed (Hsü, et al., 1977), but in fact appears to have been caused by freshwater inputs during a prolonged Late Messinian humid period throughout North Africa and the Mediterranean (Butler, 2006; Griffin, 2002). This combination of a lowered base level and plentiful river flow would have caused the extension of the As Sahabi River system throughout much of Libya and the associated down-cutting would have caused the development of deep canyons. Such landforms appear to have been extensive in the Sirt Basin where a now-buried canyon 5 km wide and more than 400 m deep has been identified (Barr and Walker, 1973; Nicolai, this volume). The extension of the As Sahabi River would have been particularly effective on its catchment boundary with Wadi Nashu because the blockage of Wadi Nashu by Al Haruj al Aswad volcano meant that it could not benefit from the Messinian base level fall, whilst the As Sahabi River system could. Consequently, Wadi Barjuj managed to capture the vast majority of the headwaters of the Wadi Nashu catchment during the Late Messinian (Drake et al., submitted) (Figure 2). It is also probable that the southernmost headwaters of the As Sahabi River expanded to such an extent that it captured rivers in the Chad Basin and then provided an outflow for Lake Megachad, a giant palaeolake that has periodically existed in the Chad Basin for the last seven million years at least (Brunet et al., 2002; Drake and Bristow, 2006). A connection to Lake Megachad is suggested by a number

The Pliocene The onset of the Pliocene marked the start of the demise of the As Sahabi River. The opening of the Atlantic floodgate at the Straits of Gibraltar (Hsü et al., 1977), and subsequent rapid Mediterreanean sea level rise at the end of the Messinian led to incursion of sea waters into the Sirt Basin and transformation of the northern of parts of the Messinian river canyons into deep estuaries and shallow marginal tidal flats

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and lagoons (Figure 3). The Mediterranean eustatic sea-level rise led to a rise of the riverine equilibrium profile and gradual silting up of the As Sahabi River courses. Whilst this was occurring volcanism and associated thermal crustal rise in the Tibisti region affected its headwaters (Reynolds and Hall, 1976) by cutting off the Lake Megachad outflow. This drastically reduced the size of the river system. In tandem with this, tectonic

subsidence in the Al Kufrah Basin caused a rejuvenation of the Al Kufrah River system and it started to expand southwards, eating into the As Sahabi River catchment (Drake et al., submitted). The expansion of the Al Kufrah River led to the initiation of an inland delta called Wadi Bleta Delta, towards the northern end of the Al Kufrah system where the river cuts through Jabal Az Zalmah and issues from the mountains onto the

Fig.ure 3. Map showing the probable river and lake systems during humid periods in the Lower Pliocene when the Mediterranean Sea had refilled. Lake Megafazzan has increased in size due to the blocking of Wadi Barjuj by the growth of Al Haruj al Aswad volcano and the initiation of Al Haruj al Abyad volcano immediately to its south. 100

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unconfined Calanscio Plain below (Figure 3). The combination of these events meant that by the end of the Pliocene there was little left of the main channel of the As Sahabi River and the most extensive part of the system was now the rivers draining the Fazzan and Tibisti Mountains into the Serir Tibisti and onwards into the Gulf of Sirt (Figure 3). During the Late Pliocene, from about 3 ma onwards, the generally humid

environment experienced by what is now the Libyan Desert began to be interrupted by arid episodes that appear to be associated with global climate changes related to the onset of high latitude glaciations (de Menocal, 2004). These early glacial cycles produced periodic aridity that presumably led to the initiation and development of the Libyan sand seas at around this time (Figure 4). In northern Libya, the Late Pliocene also produced

Figure 4. Map showing the probable river, lake and sand sea systems during humid periods in the Upper Pliocene. The map depicts the further expansion of Lake Megafazzan due to the continued expansion of Al Haruj al Aswad volcano and the initiation of Al Haruj al Abyad volcano as well as the creation of the Libyan sand seas during arid periods that had begun to regularly affect the region and the creation of a sand bar in the Gulf of Sirt. 101

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Drake, et al., (submitted) show that there are two low points to the north and south of Al Haruj al Aswad volcano containing river channels and/or fluvial gravels where overspill may have occurred (Figure 4). Overspill waters from the southern outflow point would have linked Lake MegaFazzan to the As Sahabi River system during very humid periods (Figure 4). K/Ar dating of two lava flows overlying fluvial gravels provide ages of 4.68 ± 1.52 ma and 3.43 ± 0.32 ma indicating mid Pliocene fluvial sedimentation (Drake, et al., submitted). Outflow through the northern channel would have bypassed the As Sahabi river system altogether, flowing east through a series of smaller lakes in the Zallah Trough, the Marada Trough, and finally north along the western side of Ajdabiya Trough into the Mediterranean Sea (Figure 4). The existence of fluvial sediments and landforms traversing low points on the rim of the Fazzan Basin does not necessarily mean that lake overspill occurred in these regions. Given the fact that the lake basin originated as a result of the interplay between volcanic and fluvial activity, the presence of gravels and channels can be readily explained by thermal uplift of previously existing east west flowing channels. Thus, because of the way the basin was formed, it is not possible to show conclusively that these fluvial sediments were formed by Lake MegaFazzan overspill. Therefore it is not certain that Lake Megafazzan was ever linked to the As Sahabi River system, however, if there were such a connection it would have occurred prior to 3.43 ± 0.32 ma.

considerable changes along the Gulf of Sirt coastline (Figure 4). Longshore drift transported sediments from Cyrenaica towards the west and consequently a long shore bar started to develop in the Gulf of Sirt, forming an embayment in the region that had been submerged in the Early Pliocene (Figure 4; El-Hawat and Pawellek, 2004). Further south, the Al Kufrah River continued to expand into what was the As Sahabi River catchment during humid periods as a result of continued subsidence causing further growth of the Al Kufrah River inland delta. A lake with an area of 6000 km2 periodically developed at the base of the delta fed by some of its distributary channels (di Cesare et al., 1963). In western Libya volcanic activity continued during the Pliocene with the growth and gradual southward extension of Al Haruj al Aswad volcano (Drake et al., submitted; Peregi, 2003; Ade-Hall et al., 1974). This blocked Wadi Barjuj sometime between 4 and 2 ma and increased the size of the closed basin in the Fazzan Basin by about half. A large lake known as Lake Megafazzan would now have developed within it during humid periods (Figure 4). The effect the blocking of Wadi Barjuj had on the As Sahabi River System is hard to predict with certainty. On the one hand it appears to have removed a major tributary from the As Sahabi River, however, if during exceptionally humid periods the lake become so large that overspill waters flowed out of its catchment in the region of the blockage, the entire lake basin (~350,000 km2) would have been added to the As Sahabi River system. It is not clear if this actually happened or not.

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Figure 5. Map showing the probable river, lake, and sand-sea systems during humid periods in the Pleistocene. The map shows the continued growth of Lake Megafazzan as a response to the continued development and merger of Al Haruj al Aswad and Al Haruj al Abyad volcanoes. Also depicted is Sabkhat al Qenien (Qunayyin) that was created by continued sedimentation along the sand bar that developed in the Pliocene. During the Pleistocene it finally traversed the Gulf of Sirte thus cutting off the region behind the bar from the sea. The presence of a possible lake in the middle reaches of the Al Kufrah River is also shown. continued to extend eastward, eventually cutting off a large part of the gulf from the sea thus creating an inland lake known as Sabkhat al Qunayyin (Qenien) into which the As Sahabi River now drained (Figure 5; El-Hawat and Pawellek,

The Middle and Upper Pleistocene Many palaeohydrological changes that affected the As Sahabi Ri ve r occ ur re d duri ng t h e Pleistocene. Near the riverâ&#x20AC;&#x2122;s mouth the long shore bar in Gulf of Sirt

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increased their rate of growth due to the increased severity and longevity of the aridity (de Menocal, 2004).

2004). The Al Kufrah River continued to expand its tributaries at the expense of the As Sahabi as a result of continued subsidence in the Al Kufrah Basin throughout the Pleistocene. The inland Wadi Bleta delta continued to develop in its lower reaches and it is probable that the Garet Uedda Lake existed at the base of the delta during the Pleistocene humid periods. The SRTM DEM images shows a prominent outflow channel that links the Garet Uedda Lake to Sabkhat al Qunayyin , thus at times during the Pleistocene both the As Sahabi and Al Kufra rivers would have debouched their waters into Sabkhat al Qunayyin (Figure 5). However, the connection between the two lakes was probably a rather transitory one, because numerous palaeochannels are evident on the surface of the Al Kufrah Delta that not only appear to have fed this lake, but also led directly to Sabkhat el Qunayyin and towards Egypt, presumably periodically feeding lakes in these locations. In western Libya Lake MegaFazzan continued to develop throughout the Pleistocene. Al Haruj al Aswad volcanic field continued its expansion, producing an even larger and deeper closed basin within which Lake Megafazzan continued to develop reaching an area of 135,000 km2 during humid periods (Figure 5). Sediments with this lake basin provide a rich history of climate change during the Pleistocene suggesting cycles of humidity during interglacials and aridity during glacials from 200 to at least 750 ka (Thiedig and Geyh, 2004; Armitage et al., 2007; Drake et al., submitted). As a result of the glacial arid intervals the sand seas continued to develop and spread (Figure 5) and probably

The Late Pleistocene and Holocene There is no direct evidence for substantial changes in the As Sahabi River during the Late Pleistocene and Holocene, however, there is reason to believe that a reduction in water availability during this time would have led to a reduction in the magnitude of fluvial activity and perhaps even stagnation of the river systems. There is a considerable body of evidence in the Fazzan Basin that during the last two interglacials water availability was more restricted than in previous ones, leading to the development of many small lakes, rather than the single giant lake that had existed between about 200 and 750 ka (Figure 6). For example, a lake area of ~1700 km2 existed in the lower portions of Wadi ash Shatti during the last interglacial (OIS 5) (Petit-Maire, et al., 1980; Thiedig et al., 2000; Armitage et al., 2007; Drake et al., submitted), while numerous small palaeolakes were found in the inter-dune depressions of the Ubari Sand Sea (Drake, et al., submitted). Rowan et al. (2000) provide the only other palaeoclimate information in Libya during this period and show that northeast Libya was subjected to fluvial activity indicative of a wetter climate. Though no information exists for other parts of Libya it is reasonable to assume that they experienced similar conditions. In the Holocene there is evidence for humidity in many parts of Libya. Giraudi (2005) provides evidence for fluvial activity in northwest Libya as do

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Figure 6. Map showing the probable river, lake and sand-sea systems during humid periods in the Late Pleistocene and Holocene. Note that the river systems have not changed but the lakes have become much smaller due to the decrease in water availability during humid periods. Rowan et al. (2000) in the northeast while in central and southwest Libya the Serir Tibisti system was also reactivated at this time, developing small lakes along its course from 9.3 to about 5 ka (Pachur and Hoelzmann, 2000). Numerous small Holocene palaeolake deposits are also found in the Ramlat Rabyanah in central Libya (Pachur and Hoelzmann, 2000), the Wadi Tanezzuft in southwest Libya (Cremaschi and Di Lernia, 1999), the interdune depressions of the Murzuk and Ubari

Sand Seas of the Fazzan (Cremaschi and Di Lernia, 1999; Drake et al., submitted), as well as in many of the Fazzanâ&#x20AC;&#x2122;s river basins including Wadi Barjuj (Cremaschi and Di Lernia, 1999), Wadi al Hayat (Armitage et al., 2007) and the Wadi ash Shatti (Drake et al., submitted). The latter lake appears to have been smaller than the one that developed there during the last interglacial (Drake et al., submitted) thus providing evidence for a gradual decrease in water availability in progressively more recent 105

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the As Sahabi River reducing the size of the catchment, possibly by as much as a half. As this was happening subsidence in the Kufra Basin caused the Al Kufrah River to expand and capture much of the as Sahabi Riverâ&#x20AC;&#x2122;s catchment. By the Pleistocene the Al Kufrah River dominated the palaeohydrology of eastern Libya at the expense of the As Sahabi. The Serir Tibisti Rivers were the only part of the As Sahabi River System that were largely unaffected by this process of river capture. They appear to have drained the Tibisti Mountains since the initiation of volcanism in the region. Wadi Barjuj would have been part of this system until it was blocked by the growth of Al Haruj al Aswad volcano some time between 4 and 2 ma. After this it formed part of the Fazzan Basin where a large lake known as Lake Megafazzan developed during Pliocene and Pleistocene humid periods. It is not clear if the lake ever became so large that lake overspill occurred, if it did, and this occurred to the south or Al Haruj al Aswad. Then the Fazzan basin would have been linked to the Serir Tibisti rivers forming a river system that drained much of western and central Libya. After the Early Pliocene submergence of the Gulf of Sirt, longshore drift caused a giant bar to develop. Growth continued during the Pleistocene eventually cutting off a large part of the gulf from the sea and in doing so creating an inland lake known as Sabkhat al Qunayyin. The As Sahabi River now flowed into this lake during humid periods before over-spilling the bar into the Gulf of Sirt. There appears to have been no substantial change in the As Sahabi River System during the Late Pleistocene and

interglacials. This observation is supported by the evidence from Bir Tarfawi and Dakhla Oasis in nearby Egypt (Wendorf et al., 1993; Brookes, 1993). It is therefore likely to have applied to the wider Sahara and thus the rest of Libya and suggests an associated decline in fluvial activity. SUMMARY AND CONCLUSIONS During the Late Miocene and Early Pliocene the As Sahabi River system must have been one of the biggest rivers in Africa and would have formed a corridor across the Sahara with headwaters in the Chad Basin on the southern margins of the Sahara and its mouth in the Gulf of Sirt. The origins of the river system are not known precisely but must have followed the inherited structural troughs in the Sirt rift complex during the Miocene. The formation of the Serir Tibisti tributaries of the As Sahabi system presumably were associated with the development of the initiation of volcanism in the eastern Tibisti region at about 9.7 ma (Reynolds and Hall, 1976) and the associated development of the Tibisti Mountains. The Messinian draw-down of the Mediterranean Sea caused a major expansion of this river system and the development of an extensive channel system throughout much of Libya and Chad. By the Early Pliocene the Mediterranean had refilled causing the Gulf of Sirt to be submerged, and marine and fluvio-estuarine sediments to infill much of the northern reaches of the As Sahabi River system. As the Pliocene progressed the As Sahabi River gradually declined. Uplift on the eastern flanks of the Tibisti Mountains stopped the outflow of Lake Megachad into

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Busrewil). London, Academic Press, 463500.

Holocene. Though the river system was active during humid periods, a reduction in water availability appears to have led to a decline in fluvial activity.

BOAZ, N.T., GAZIRY, A.W., DE HEINZELIN and EL-ARNAUTI, A. (1982). Results from the International Sahabi Research Project. University of Garyounis, Benghazi. Garyounis Scientific Bull. Special Issue 4.

ACKNOWLEDGEMENTS We would like to thank Garyounis University Research Centre for their support and Noel Boaz for encouraging us to develop this research and inviting us to present it.

BOAZ, N.T., EL-ARNAUTI, A., GAZIRY, A.W., DE HEINZELIN, J. and BOAZ, D.D. (eds) (1987). Neogene Paleontology and Geology of Sahabi. New York, Alan Liss.

REFERENCES BRUNET, M., GUY , F. , PILBEAM, D., MACKAYE, H.T., LIKIUS, A., AHOUNTA, D., B E A U V I L A I N , A., B L O N D E L , C., BOCHERENS, H., BOISSERIE, J-R., DE BONIS, L., COPPENS, Y., DEJAX, J., DENYS, C., DURINGER, P., EISENMANN, V., FANONE, G., FRONTY, P., GERAADS, D., LEHMANN, T., LIHOREAU, F., LOUCHART, A., MAHAMAT, A., MERCERON, G., MOUCHELIN, G., OTERO, O., CAMPOMANES, P., .MARCIA DE LEON, P., RAGE, P., SAPANET, J-C. , SCHUSTER, M., SUDRE, M., TASSY, J., VALENTIN, P., VIGNAUD, P. ,VIRIOT, L, and ZAZZO,C. (2002). A new hominid from the Upper Miocene of Chad, Central Africa. Nature 418, 145-151.

ADE-HALL, F.M., REYNOLDS, P.H., DAGLEY, P., MUSSET, A.G., HUBBARD, T.B. and KLITZSCH, E. (1974). Studies of North African Cenozoic volcanic areas alHaruj Assuad, Libya. Canadian Journal of Earth Sciences 11, 998-1006. ARMITAGE, S.J., DRAKE, N.A., STOKES, S., EL-HAWAT, A., SALEM, M.J., WHITE, K., TURNER, P. and MCLAREN, S.J. (2007). Multiple phases of North African humidity recorded in lacustrine sediments from the Fazzan Basin, Libyan Sahara. Quaternary Geochronology 2, 181-186. BARR, F.T. and WALKER, B.R. (1973). Late Tertiary channel system in northern Libya and its implication on Mediterranean sea level changes. In: Initial Report Deep Sea Drilling Project, Leg 13. (eds W.B.F. Ryan and K.J. Hs端),1244-1251.

BUSREWIL, M. T. and WADSWORTH, W. J. (1980). The basanitic volcanoes of the Gharyan area, NW Libya. In: The Geology of Libya, Volume 2 (eds M. J. Salem and M. T. Busrewil), Academic Press, London, 1095-1105. BUTLER, R.W.H., (2006). When the Mediterranean dried out: Forensics of a geocatastrophe. Geotimes. 12, 20-23.

BENFIELD, A.C. and WRIGHT, E.P. (1980). Post-Eocene sedimentation in the eastern Sirt Basin, Libya. In: The Geology of Libya. Volume 2 (eds M.J. Salem and M. T.

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years. Palaeogeography, Palaeoclimatology, Palaeoecology.

CREMASCHI, M. and DI LERNIA, S. (1999). Holocene climate change and cultural dynamics in the Libyan Sahara. African Archaeological Review 16, 211-238.

EL-HAWAT, A. and PAWELLEK, T. (2004). A Field Guidebook to the Geology of Sirt Basin, Libya. Dea North Africa / Middle East GmbH, 69 p.

DE HEINZELIN, GAZIRY, A.W.

J., EL-ARNAUTI, A. and (1980). A preliminary revision of the Sahabi Formation. In: Second Symposium on the Geology of Libya (eds M.J. Salem and M. T. Busrewil). Academic Press, London, 127-136.

GIRAUDI, C. (2005). Eolian sand in peridesert northwestern Libya and implications for Late Pleistocene and Holocene Sahara expansions. Palaeogeography, Palaeoclimatology, Palaeoecology 218, 161-173.

DE MENOCAL, P.B. (2004). African climate change and faunal evolution during the Pliocene-Pleistocene. Earth and Plant. Sci. Lett. 220, 1-2, 3-24.

GRIFFIN, D.L. (2002). Aridity and humidity: Two aspects of the late Miocene climate of North Afri ca. Palaeogeography, Palaeoclimatology, Palaeoecology 182, 6591.

DI CESARE, F., FRAANCHINO and SOMMARUGA, C. (1963). The PlioceneQuaternary of Giarabub Erg region, Revue de L’inststut Francais de Petrole, 18, 13441362.

GRIFFIN, D.L. (2006). Late Neogene Sahabi rivers of the Sahara and their climatic and environmental implications for the Chad Basin. Journal of the Geological Society 163, 905-921.

DRAKE, N.A. and BRISTOW, C. (2006). Shorelines in the Sahara: Geomorphological evidence for an enhanced monsoon from palaeolake Megachad. The Holocene 16, 901-911.

HSÜ, K.H., MONTADERT, L., BERNOULLI, D., CITA, M.B., ERICKSON, A., GARRISON, R.E., KIDD, R.B., MELIERES, F., MULLER, C. and WRIGHT, R. (1977). History of the Mediterranean salinity crisis. Nature 267, 399-403.

DRAKE, N.A., WHITE K.H., EL-HAWAT A., SALEM, M.J., ARMITAGE, S.J., TURNER, P. and MCLAREN, S. (Submitted) The palaeoclimate record of the Lake Megafazzan Basin, Libyan Sahara. Quaternary Science Reviews.

LIHOREAU, F., BOISSERIE, J-R., VIRIOT, L., COPPENS, Y., LIKIUS, A., MACKAYE, T.H., TAFFOREAU, P., VIGNAUD, P. and BRUNET, M. (2006). Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince, Proceedings of the National Academy of Science 103, 8763-8767.

DRAKE, N.A., EL-HAWAT, A.S., TURNER, P., ARMITAGE, S.J., SALEM, M.J., WHITE, K.H. and MCLAREN S. (Submitted) Palaeohydrology of the Fazzan Basin and surrounding regions: The last 7 million

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PACHUR, H-J. and HOELZMANN, P. (2000). Late Quaternary palaeoecology and palaeoclimates of the eastern Sahara. Journal of African Earth Sciences 30, 929939. PETIT-MAIRE, N., DELIBRIAS, G. and GAVEN, C. (1980). Pleistocene lakes in the Shati area, Fazzan. Palaeoecology of Africa 12, 289-295. PEREGI, Z. (2003). Geological Map of Libya 1: 250,000, Sheet: Al Haruj al Abyad Ng 33-8; Explanatory Booklet. Budapest and Tripoli, Geological Institute of Hungary and Industrial Research Centre. REYNOLDS, O. and HALL, J.M. (1976). Absolute age and palaeomagnetic results from the Tibesti-Garian (Tripoli) North African Cenozoic volcanic line. EOS: Transactions of the American Geophysical Union 57, 904. ROWAN, J.S., BLACK, S., MACKLIN, M.G., TABNER, B.J., and DORE, J. (2000). Quaternary environmental change in Cyrenaica evidenced by U-Th, ESR and OSL dating of coastal alluvial fan sequences. Libyan Studies 31, 5-16. WENDORF, F., SCHILD, R., AND CLOSE, A. (1993). Summary and conclusions. In: Egypt during the Last Interglacial: The Middle Paleolithic of Bir Tarfawi and Bir Sahara East (eds F. Wendorf, R. Schild and A.E. Close). New York, Plenum, 412423.

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New remains of Crocodylus checchiai Maccagno 1947 (Crocodylia, Crocodylidae) from the Late Miocene of As Sahabi, Libya

MASSIMO DELFINO

ABSTRACT Previously unpublished skull and lower jaw fragments of a short-snouted crocodylian from the Late Miocene of As Sahabi, Libya are here described and referred to Crocodylus checchiai Maccagno 1947 on the basis of the evident convexity visible in the proximal area of the nasals. Because C. checchiai has not been analysed in a phylogenetic context it is not possible to state if it is really related to the genus Crocodylus or if it belongs to the osteolaemine clade, represented in the extant African fauna only by the genus Osteolaemus. Recent phylogenetic analyses of many Neogene African and Malagasy crocodylids reveals osteolaemine affinities but the presence of a crocodyline in the Late Miocene-Early Pliocene of southern Italy (which could maybe share the presence of a dorsal medial boss on the rostrum) could suggest that C. checchiai is a crocodyline, too. A direct review of the old collections and new materials of C. checchiai is needed to properly understand its phylogenetic relationships.

Massimo Delfino, Dipartimento di Scienze della Terra, UniversitĂ di Firenze, Via G. La Pira 4, 50121 Firenze, Italy, massimo.delfino@unifi.it

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Crocodylus (as defined by Brochu, 2000) are explicitly discussed by Maccagno (1947, 1952) or subsequent authors, nor are they visible in the available figures. The taxonomy of the African fossil and extant crocodylians has been considerably modified in recent years. Several Late Neogene taxa formerly referred to the genus Crocodylus have been shifted to other genera after a cladistic analysis. For Africa and Madagascar, noteworthy are the cases of Crocodylus lloydi which is now Rimasuchus lloydi according to Storrs (2003), and of Crocodylus robustus which has been recently referred to a new genus by Brochu (2007). Also the three African extant crocodylians, formerly grouped in the genus Crocodylus, are now considered to belong to three different genera (McAlily et al., 2006): Crocodylus niloticus, Mecistops cataphractus and Osteolaemus tetraspis (the splitting of some populations of these taxa into different species is not taken into consideration in this paper). Therefore, a proper assessment of the phylogenetic relationships of C. checchiai could reveal unexpected relationships. C. checchiai is clearly a short-snouted crocodylid but it is not clear if it belongs to the clade of the Crocodylinae or to that of the Osteolaeminae. The previously mentioned R. lloydi and “C.” robustus, as well as “C.” pigotti and Euthecodon arambourgi, are now considered as being Osteolaeminae and according to Brochu (2007) also C. checchiai could belong to this group. As a preliminary step for the revision of the type material of C. checchiai, a few previously unpublished remains of a short-snouted crocodylid from As Sahabi are described here. These skull and lower jaw elements are from one

INTRODUCTION The reptile fauna from the Late Miocene locality of As Sahabi in Libya has been known since the first decades of the last century when D’Erasmo (1933, 1934) reported the presence of crocodylian and turtle remains. Since then, the knowledge of the reptiles of As Sahabi grew considerably and now the faunal list includes several large-sized taxa: the crocodylians Euthecodon sp. and Crocodylus checchiai Maccagno 1947, the chelonians Trionyx triunguis and Centrochelys aff. C. sulcata and a booid snake, probably belonging to genus Python (Maccagno, 1947, 1952; Hecht, 1987; Wood, 1987; de Lapparent de Broin, 2000). The presence of some other taxa, such as undetermined emydid turtles, the alligatoroid Diplocynodon, and longsnouted crocodylid tomistomines (? Tomistomidae indet.), has not been confirmed by later analyses (see D’Erasmo, 1933, 1934; Boaz et al., 1979; Delfino, 2008, and literature therein). The only reptile species so far erected on the basis of remains from As Sahabi is the crocodylid Crocodylus checchiai. This species has been described on the basis of well-preserved skulls and lower jaws and, according to its author, it could be phylogenetically related to the Asian species C. palaeindicus, C. palustris and C. sivalensis (the latter species is a junior synonym of C. palaeindicus; Brochu, 2000). Later researchers suggested relationships with the African C. lloydi and C. niloticus or the New World Crocodylus clade (see Delfino, 2008, for a summary). C. checchiai has never been revised since its original description and its phylogenetic relationships are doubtful. None of the characters diagnosing the genus

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individual from Locality P24A (Member U1 of the Sahabi Formation), and belong to the collections of the University of Garyounis Earth Science Museum.

represent a first attempt of scoring the characters of phylogenetic relevance for a cladistic analysis (see Brochu, 2007, and references therein for the character list). Such analysis goes beyond the goals of this paper and therefore has not been performed here. The status of the characters assessed on the basis of specimen 30P24A will be incorporated into the matrix that is going to be prepared on the basis of the type specimens.

DESCRIPTION The specimen 30P24A consists of a highly fragmentary skull and lower jaw of a rather large crocodylian. The following description concerns the most informative remains only. The numbers in parentheses

Figure 1 â&#x20AC;&#x201C; Crocodylus checchiai 30P24A â&#x20AC;&#x201C; A, preserved portion of the dorsal skull surface; B, preserved portion of the skull table; C, isolated left quadrate; D, preserved portion of the palatal surface; E, isolated teeth. Scale bars correspond to 50 mm except in E where the bar corresponds to 20 mm. 113

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convex in the posterior one. Such convexity is visible not only in lateral but also in anterior view because the lacrimals are located at a lower level than the top of the arched nasals. In dorsal view, the nasals slightly widen in the anterior region but abruptly shrink between the posterior processes of the premaxillae. Posteriorly, the nasals are damaged or broken off (the left one) but it appears that they overlapped significantly over the anterior process of the frontal. The maxillae are represented by a few fragments of their dorsal surface which are attached to the premaxillae, the right nasal, the lacrimals and the right jugal. The fragment of the left maxilla attached to the nasal and the lacrimal allows one to exclude the presence of a posterior process of the maxilla within the lacrimal or between lacrimal and prefrontal. Lacrimals are longer than prefrontals. Their posterior region forms the anterior rim of the orbits; a roundish foramen, with a diameter or about 3 mm, placed in this area has been considered the lacrimal duct. The prefrontals preserve the dorsal surface only and therefore they do not offer any information about the morphology of the prefrontal pillars. It is clear that the prefrontals were separated from each other by the anterior process of the frontal posteriorly and by the nasals anteriorly. The anterior process of the frontal is moderately long (it reaches approximately the mid of the prefrontals) and flat because it does not have any transversal ridge. The remnants of the posterior region of the frontal are moderately concave and apparently not raised in a ridge along the orbital rim (about 2 cm of the orbital rim is preserved on the right side). The

Skull The largest portion of the skull is represented by the posterior region of both the premaxillae, fragments of the maxillae, the nasals, fragment of the prefrontals and of the left lacrimal, a nearly complete right lacrimal, the anterior portion of the frontal, the nearly complete right jugal and a fragment of the right quadratojugal (Figure 1a). The elements of the dorsal surface of the skull are completed by the isolated left jugal, by the posterior region of the frontal still joined to the anterior portion of the parietal and fragments of both the postorbitals (Figure 1b), as well as by the isolated left quadrate (Figure 1c). The palatal surface is represented by the region corresponding to the lateral, medial and posterior rim of the suborbital fenestrae; therefore portions of both the palatines, pterygoids and ectopterygoids are preserved (Figure 1d). The ornamentation of the entire dorsal skull surface (with the exception of the quadrate, thye dorsal surface of which is smooth) is represented by irregular pits separated by ridges. In the lateral area of the jugals the pits tend to be wider, elongate, and anamostosed. Wider pits are also present on the frontal. The premaxillae preserve only the dorsal surface of the posterior region. Their dorsal processes are not particularly elongate. The premaxillae form at least the posterolateral rim of the naris (without the development of any notch laterally to it; but do not form the central sector of the posterior rim because the nasals reach the naris forming a few millimetres of the rim. The nasals are characterised by being rather flat (or imperceptibly concave) in their anterior region and remarkably

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angle, that the lateral edges of palatine are nearly parallel posteriorly, and that due to a wide bend in the anteromedial sector of the edge of the ectopterygoid (just anterior to the ectopterygoid-pterygoid suture) the suborbital fenestrae show a significant posteromedial notch. The absence of the choana in the posterior region of the palatines and in the anterior region of the pterygoids is considered as an evidence that it opened in the posterior region of the pterygoids and that therefore the choana was entirely surrounded by these elements. Both the ectopterygoids have a broken off anterior tip so that it is not possible to evaluate its shape (forked or not).

frontoparietal suture is slightly concave anteriorly and it is entirely developed on the skull table because postorbitals separate the frontal from the supratemporal fenestrae. The parietal hosts therefore the anteromedial rim of the supratemporal fenestrae. The latter show a rim developed into a continuous thin ridge; their rim does not overhang the fossae because the anteromedial surface of the fossae slopes gradually in a posterolateral direction. Jugals are relatively well-preserved; their dorsal margin along the infratemporal fenestra and the orbit is raised into a rather sharp rim. The postorbital bar is clearly inset to the rim. The inner surface, in correspondence of the sutural area with the ectopterygoid, is completely broken in the left jugal but much less in the case of the right one, so that a relatively large medial jugal foramen and two other smaller foramina are clearly visible. It is not clear if the jugal forms the posterior angle of the infratemporal fenestra or if the suture between jugal and quadratojugal reaches such an angle. From the scars on the medial surface of the postorbital bar it is possible to state that the ectopterygoid extended significantly along the medial face of the bar. The quadratojugal is only minimally preserved. It does not send any anterior process along the lower temporal bar. The quadrate shows a medially placed foramen aereum. Despite the quadrate condyle being heavily eroded, the medial hemicondyle is distinctly expanded. The palatal surface is represented by few fragmentary elements only but they allow one to state that the palatinepterygoid suture reaches the suborbital fenestrae relatively far from their posterior

Lower Jaw The lower jaws are much more incomplete than the skull and so damaged that it is not possible to provide any detailed description. The largest fragment of the left jaw, probably corresponding to a medial section, still preserves remnants of the splenial and shows some depressions on the lateral side of the dentary, depressions corresponding to the interalveolar spaces and therefore demostrating that the maxillary teeth were visible in occlusion on the lateral side of the snout. Dentition Most of the available teeth are represented by small isolated fragments. The few well-preserved teeth (Figure 1e) allow perceiving a considerable variation in terms of size and shape. Some teeth are slender and elongate (the largest has a

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belongs to the genus Crocodylus (sensu Brochu, 2000), the presence of a median dorsal boss could indicate a direct relationship with the New World clade or, alternatively, the rostrum boss could have been independently acquired in the American and in the African lineages. The last conclusion (independent evolution) can be also drawn if C. checchiai is discovered to be a member of the osteolaemine clade. The potential confirmation of direct phylogenetic relationships between C. checchiai and the New World Crocodylus clade would fit in the extensive long-range oceanic dispersals that shaped the paleodistribution of several crocodylian taxa (Brochu, 2001, 2007). It is interesting to underline that the presence of such a boss could be present also in the still not identified Crocodylus species recently described form the Late Miocene-Early Pliocene of Southern Italy, which probably dispersed from Africa to Europe during the Late Miocene (Delfino, et al., 2007). The only available maxilla from this locality (a juvenile fragmentary maxilla) shows at the same time one of the few autoapomorphic characters of Crocodylus (the blind pockets in the caviconchal recess) and also a peculiar parasagittal groove along the nasalmaxillary suture. Brochu (1997) reported the presence of such a boss in the hatchling of the American species C. acutus and inferred the presence of this character throughout post-hatching ontogeny. Therefore, it could be present in the juvenile fossil maxilla from Italy. However, the boss is described to form a groove along the nasal-maxillary suture (Brochu, 1997) and not on the maxilla parallel to such a

crown 27 mm tall and 19 mm wide at the base) while others are more robust and blunt (one of the smallest has a crown 12 mm tall and 12.5 mm wide at the base). The crowns are characterised by anterior and posterior mesiodistal keels delimiting a labial surface wider than the lingual one. The crown surface is rather smooth in the case of the elongated teeth (except for the presence of up to 10 small ridges on the labial area), whereas it is finely wrinkled with some sort of granulations in the case of the blunt teeth (the wrinkles intersect also the mesiodistal keels but do not produce denticles). RESULTS AND DISCUSSION The new crocodylian remains from As Sahabi belong to a short-snouted crocodylid that can be identified with confidence as Crocodylus checchiai, the sole species of this group which is present in this locality (Delfino, 2008). The general appearance of the preserved skeletal elements is congruent with that of skulls referred to C. checchiai. Further diagnostic is the evident “preorbital promontory” (as named by Hecht, 1987) or “median dorsal boss” of the rostrum (as named by Brochu, 1997). Such a boss, already described in the Libyan species by Maccagno (1947, 1952) and by Hecht (1987), actually represents one of the characters supporting the New World clade of extant Crocodylus (Brochu, 1997, 2000). Its presence in an African Late Neogene extinct taxon is quite interesting and, due to its unknown phylogenetic relationships, different scenarios (to be tested with a proper phylogenetic analysis) can be proposed. If C. checchiai really

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REFERENCES

suture. The juvenile morphology of this structure should be studied in detail in order to properly assess the condition shown by the Italian fossil and therefore its indirect bearing on the C. checchiai issue.

BOAZ, N.T., GAZIRY, A.W. and ELARNAUTI, A. (1979). New fossil finds from the Libyan Upper Neogene site of Sahabi. Nature 280, 137-140.

CONCLUSIONS BROCHU, C.A. (1997). Phylogenetic Systematics and Taxonomy of Crocodylia. Ph.D. thesis, University of Texas, Austin, 467 p.

The crocodylian remains from As Sahabi collectively catalogued under the accession number 30P24A clearly represent a partial skull of Crocodylus checchiai. This taxon shares with the New World Crocodylus species the presence of a unique character, a median dorsal boss on the rostrum. A proper assessment of the taxonomy and phylogenetic relationships of the remains of this species belonging to the historical collections of Tripoli and Rome, as well as those collected during the recent field surveys by the ELNRP team, could be crucial for the knowledge of the evolutionary history of the Mediterranean Neogene crocodylians, as well as for that of the extant African crocodylians and their possible relationships with the New World clade of Crocodylus.

BROCHU, C.A. (2000). Phylogenetic relationships and divergence timing of Crocodylus based on morphology and the fossil record. Copeia 2000 (3), 657-673. BROCHU, C.A. (2001). Congruence between physiology, phylogenetics and the fossil record on crocodylian historical biogeography. In: Crocodilian Biology and Evolution (eds G.C. Grigg, F. Seebacher and C.E. Franklin). Chipping Norton, Surrey Betty and Sons, 9-28. BROCHU, C.A. (2007). Morphology, relationships, and biogeographical significance of an extinct horned crocodile (Crocodylia, Crocodylidae) from the Quaternary of Madagascar. Zool. J. Linn. Soc. 150, 835-863.

ACKNOWLEDGEMENTS The author would like to thank N. Boaz and A. El-Arnauti for their energy in organizing the East Libya Neogene Research Project (ELNRP) and for the invitation to contribute to this volume. N. Boaz and P. Pavlakis kindly favoured this study solving “logistic” problems. This paper is framed within a wider project on Late Neogene vertebrate evolution developed at the University of Florence (coordinator Lorenzo Rook).

DELFINO, M. (2008). Late Neogene crocodylian faunas from Libya and the Mediterranean area. In: The Geology of East Libya, vol. III. Sedimentary Basins of Libya (eds M.J. Salem, A. El-Arnauti and A. El-Sogher Saleh). Earth Science Society of Libya, Tripoli. DELFINO, M, BÖHME, M. and ROOK, L. (2007). First European evidence for

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MCALILY, L.R., WILLIS, R.E., RAY, D.A., WHITE , P.S., B ROCHU , C.A. and DENSMORE, L.D. (2006). Are crocodiles really monophyletic? Evidence for subdivisions from sequence and morphological data. Molec. Phylogen. Evol. 39, 16–32.

transcontinental dispersal of Crocodylus (late Neogene of southern Italy). Zool. J. Linn. Soc. 149, 293-307. D'ERASMO, G. (1933). Sui resti di vertebrati terziari raccolti nella Sirtica dalla missione della Reale Accademia d’Italia (1931). Atti R. Accad. Naz. Lincei, Rend. Cl. Sci. Fis. Mat. Nat. (ser. 6) 17, 656-658.

STORRS, G.W. (2003). Late Miocene-Early Pliocene crocodilian fauna of Lothagam, Southwest Turkana Basin, Kenya. In: Lothagam: The Dawn of Humanity in Eastern Africa (eds M.G. Leakey and J.M. Harris). New York, Columbia University Press, 137-159.

D'ERASMO, G. (1934). Su alcuni avanzi di vertebrati terziari della Sirtica. Missione Scientifica della Reale Accademia Italiana a Cufra (1931-IX), (Studi Paleontologici e Litologici sulla Cirenaica e sulla Tripolitania Orientale) 3, 257-279.

WOOD, R.C. (1987). 8. Fossil turtles from the Sahabi Formation. In: Neogene Palaeontology and Geology of Sahabi (eds N.T. Boaz, A. El-Arnauti, A. W. Gaziry, J. De Heinzelin and D. Dechant Boaz). New York, Liss, 107-112.

HECHT, M.K. (1987). Fossil snakes and crocodilians from the Sahabi Formation of Libya. In: Neogene Palaeontology and Geology of Sahabi (eds N.T. Boaz, A. ElArnauti, A. Wahid Gaziry, J. de Heinzelin and D. Dechant Boaz). New York, Liss, 101-106. LAPPARENT DE BROIN, F. (2000). African chelonians from the Jurassic to the present: Phases of development and preliminary catalogue of the fossil record. Paleont. Afr. 36, 43-82. DE

MACCAGNO, A.M. (1947). Descrizione di una nuova specie di "Crocodilus" del Giacimento di Sahabi (Sirtica). Atti Accad. Naz. Lincei: Mem. Cl. Sci. Fis. Mat. Nat., Sez. II, Fis., Chim., Geol., Paleont. Min. (ser. 8) 1(2), 61-96. MACCAGNO, A.M. (1952). I coccodrilli di Sahabi. Rend. Accad. Naz. Quaranta, ser. 4, 3, 73-117.

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Overview of the Fossil Avian Fauna from the Sahabi Formation DIMITRIOS MICHAILIDIS

ABSTRACT Palaeontological field expeditions for the period 1978 to 1981 at the Sahabi Formation of Libya led to the collection of a variety of avian skeletal remains which indicate the presence of at least ten species. During the February-March 2007 field season of the E.L.N.R.P. in As Sahabi additional avian material was collected. This paper reports the preliminary evaluation of the new finds. In total 21 avian skeletal fragments were collected, with humeri being the most abundant. Appropriate measurements were made in an attempt to classify the material to the ordinal level. The current finds support the results of the analysis of the older As Sahabi avian material in that a mostly water-tied avifauna is represented, with a strong presence of Pelecaniiformes and Anseriformes. Future work will involve the use of comparative osteological collections as a means of attaining a more secure and detailed taxonomic allocation of the current fossil avian material.

Dimitrios Michailidis, Department of Historical Geology and Palaeontology, Faculty of Geology and Geoenvironment, University of Athens, Athens, Greece, dmichailidis@geol.uoa.gr

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Pelecaniformes Phalacrocoracidae Phalacrocorax sp. Anhingidae Anhinga sp. Pelecanidae Pelecanus sp. Falconiformes Accipitridae Accipitridarum gen. sp. Anseriformes Anatidae Anatidarum gen. sp. A Anatidarum gen. sp. B Anatidarum gen. sp. C Anatidarum gen. sp. D

INTRODUCTION The Sahabi Formation of Libya is significant among North African MioPliocene fossiliferous sites in preserving a large and diverse palaeofauna (Boaz, 1996). The analysis of different elements of a palaeofauna can provide supplementary information concerning the palaeoecology and zoogeography of a fossil site. In particular, the As Sahabi fossil avian remains can be of some use in reconstructing the local Miocene palaeoenvironment. Walker and Dyke (2006) suggest that avian fossils are especially valuable for the reconstruction of t h e p a l a e o e n vi r onme n t , b e c a us e osteological differences between Miocene birds and their nearest recent relatives are minimal. On the other hand, the considerable environmental differences between the Miocene and the present time as well as the difficulty in assessing the significance of even minor osteological changes in organisms, make it hard to extract significant palaeoecological information from fragmentary remains without the additional use of geologic and taphonomic evidence (e.g. Vrba, 1980, Behrensmeyer, 1975). During five past field seasons (from 1978 to 1981) enough avian material was collected to allow the identification of 10 avian species (Ballmann, 1987). The resulting avifaunal list is as follows: AVES Ciconiiformes Ciconiidae Leptoptilos sp. Ciconiidarum gen. sp.

In this preliminary study the discovery of additional avian fossil material is reported. During the surface survey of the winter field season during February to March, 2007 of the East Libya Neogene Research Project at the Sahabi Formation of Libya, a number of identifiable avian skeletal elements were collected, from 11 different localities. Table 1 lists the different skeletal elements recovered. In total 21 skeletal fragments were collected. Four out of the 21 elements are unidentifiable. Humeri are the most abundant skeletal elements. METHODS The osteological nomenclature follows Baumel et al. (1993). The following abbreviations in describing the elements are used: dist.- distal; prox.-proximal; caud.caudal; cran.- cranial; dors.- dorsal; ventr.ventral; frag.- fragment; l- left; r- right;

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cor.- coracoid; hum.- humerus; tmttarsometatarsus; phal.- phalanx; uln.- ulna. Measurements were made with Mitutoyo dial callipers with an accuracy of 0.02 mm. The measurements are abbreviated as follows: L- greatest length; PW- proximal width; DW- distal width; PH- proximal height; DH- distal height. In the coracoid the following measurement is used: ALarticulation length (from the proximal end of processus acrocoracoideus to the distal end of processus procoracoideus).

Some elements of the morphology of the proximal end of the humerus are preserved on 4P204A (Figure 1). In caudal view the area around the fossa pneumotricipitalis is badly worn, therefore, minimal information can be extracted. The overall shape of the caput humeri is apparent as well as a possibly shallow incisura capitis humeri. In cranial view, a deep sulcus transversus can be observed. Miller (1966) contrasts Phalacrocoracidae and Anhingidae by a series of characters one of which is the sulcus transversus on the proximal humerus. He states that in anhingas the sulcus transversus is short and deep only medially while in cormorants it is long and deep. It extends transversely to, but is narrowly separated from the impressio coracobrachialis (Miller, 1966, p. 315). In 4P204A the condition of the sulcus

RESULTS AND DISCUSSION Humeri 4P204A, Proximal fragment humerus. Order: Pelecaniformes Measurements: PW: 20.54mm

left

Figure 1. 4 P204A, Prox. frag. of l. hum. (Figure 1a, caudal view; Figure 1b, cranial view) 121

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Table 1. Table of fossil avian material from the winter 2007 field season of the ELNRP at the Sahabi Formation.

Fossil Avian material, Sahabi Formation. Winter 2007 ELNRP field season SpecNo.

Locality

Skeletal Element

Position

Side

UNGUAL PHALANX

105

UNGUAL PHALANX

103

PHALANX

FEMUR

DISTAL

ULNA

DISTAL

LEFT

109

ULNA

TARSOMETATARSUS

BONE INDET-ULNA DISTAL

204

BONE INDET-SCAPULA

BONE INDET-CORACOID PROXIMAL

BONE INDET

CORACOID

PROXIMAL

RIGHT

CORACOID

PROXIMAL

RIGHT

HUMERUS

DISTAL

LEFT

HUMERUS

DISTAL

LEFT

HUMERUS

DISTAL

LEFT

103

HUMERUS

PROXIMAL

LEFT

201

HUMERUS

DISTAL

RIGHT

204

HUMERUS

PROXIMAL

LEFT

204

HUMERUS

DISTAL

RIGHT

RIGHT PROXIMAL

RIGHT

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transversus is similar to that observed by Miller (1966) for the anhingas.

(Figure 2). In caudal view the elongate crista deltopectoralis is rotated over the cranial surface. The margo caudalis extends to the tuberculum dorsale. In cranial view, a short and medially deep sulcus transversus can be observed, a condition similar to that seen in 4P204A, a proximal fragment of left humerus.

20P62A, right humerus. Order: Pelecaniformes Measurements: L: 107.18mm, PW: 18.79mm, DW: 10.34mm. Elongate and slender humerus

Figure 2. 20P62A, right humerus (Above, caudal view; Below, cranial view) 11 P204A, distal fragment of right humerus. Order: Pelecaniformes Measurements: DW: 17.17mm, DH: 12.12mm. This humeral fragment (Figure 3) is similar in size and morphology to 1P109A (hum., l., dist.) and 93 P16A (hum., r., dist.) identified as Anhinga sp. by Ballmann (1987).

In cranial view the prominent thick condylus dorsalis, is almost parallel to the axis proximodistalis of the humerus. The small condylus ventralis is angled at about 50 degrees to the axis proximodistalis of the humerus. The tuberculum supracondylare ventrale is large. The fossa musculi brachialis is shallow and ovoid in shape. Laterally, it is more depressed, forming a 123

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Figure 3. 11P204A, a distal fragment, right humerus (left, caudal view), and 1P109A, a distal fragment, left humerus (right, cranial view)

Figure 4. Figure 4a, caudal view of 5P201A distal frag.ment right hum.erus, 5P16C distal frag.ment, left humerus, and 1P47A, a distal frag.ment, right humerus; Figure 4b, cranial view of 5P201A, distal fragment, r.ight humerus 124

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ridge on its border with the corpus humeri. In caudal view the fossa olecrani is broad and deeply excavated. The processus flexorius is strongly produced laterally.

Ulna 11P37A. Distal fragment of left ulna. Order: Pelecaniformes Measurements: DW: 11.84 mm, DH: 6.38 mm. Similar in size and morphology (Figure 5) to 2P26A (ulna, r., dist.), identified by Ballmann (1987) as Anhinga sp.

5P201A, distal fragment of right humerus. Order: Anseriformes Measurements: DH: 17.61mm. Similar in size and overall morphology (Figure 4) to 1P47A (hum., r., dist.) identified by Ballmann (1987) as Anatidarum gen. sp. A.

Coracoid 6P16C, right, proximal coracoid. Order: Anseriformes Measurements: AL: 20.20 mm In dorsal view, the facies articularis humeralis faces dorso-laterally. The facies articularis humeralis is rounded and concave (Figure 6). Mayr and Weidig (2004) state that a cup-like facies articularis scapularis is seen in Anseriformes. There appear to be large pneumatic foramina penetrating the whole length of the processus

5P16C, distal fragment of left humerus. Order: Anseriformes Measurements: DW: 32.79mm. This specimen (Figure 4) looks identical to 1P47A (hum., r., dist.) identified by Ballmann (1987) as Anatidarum gen. sp. A.

Figure 5. 2 P26A dist. frag. r. uln. (left) and 11P37A dist. frag. l. uln. (Right) (Figure 5a, caudal view; Figure 5b, cranial view) 125

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Figure 6. 6 P15C, prox. frag. r. cor. (Figure 6a, dorsal view, Figure 6b, ventral view).

Figure 7. Figure 7a: 26P14A, phal. ungualis (left) and 105P61A phal. ungualis (right). Figures 7b and 7c: 11P103A, Pedal phalanx (Figure 7b, dorsal view; Figure 7c, plantar view).

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acrocoracoideus. Short (1969) argues that in Anseriformes there are pneumatic foramina under the brachial tuberosity, which are large in geese and small in swans. The sulcus m. supracoracoidei is excavated under the facies articularis humeralis and there appears to be no foramen nervi supracoracoidei.

CONCLUSIONS This study has reported the discovery of additional fossil avian material from the Sahabi Formation and presented a preliminary analysis of the material. Future analysis of the material will focus on the use of comparative osteological collections as a means of attaining a more secure and detailed taxonomic allocation of the current fossil avian material. Ballmann (1987) reports the presence of a large Anatidarum gen sp. the size of modern swans with a mixture of morphological characteristics found in extant swans, geese, and Tadorninae. The importance of this find lies in that it is the only possibly European element of the avifauna which in general is most akin to the modern Ethiopian region (Ballmann, 1987). In the winter field season of February-March, 2007 at As Sahabi two distal humeri (5P201A and 5P16C) were discovered that are identical to the 1P47A distal humeral fragment identified as Anatidarum gen. sp. A. These finds reinforce the view of the presence of a European element in the As Sahabi palaeoavifauna. The current finds support the results of Ballmannâ&#x20AC;&#x2122;s (1987) analysis of the As Sahabi avian material in that mostly water birds are represented, with a strong presence of Pelecaniiformes and Anseriformes.

Phalanges 26P14A, Phalanx ungualis. Order: Falconiformes Measurements: L: 21.07 mm, PW: 5.88 mm, PH: 10.75 mm Ungual phalanx (Figure 7a) with a pair of canals lateral and medial to tuberculum flexorium. Absence of sulcus neurovascularis in the form of a groove. Mayr and Clarke (2003) state that Falconiiformes share a derived morphology of the pedal claws in that a sulcus neurovascularis is missing and in the presence of a pair of canals next to the tuberculum flexorium. 105P61A, Phalanx ungualis. Order: Strigiformes Measurements: PW: 5.51 mm, PH: 13.50 mm Strongly curved ungual phalanx (Figure 7a) with a strong ball-shaped tuberculum flexorium. Its lateral side is excavated by a prominent groove (sulcus neurovascularis) that seems to extend throughout the osseous claw.

ACKNOWLEDGEMENTS I am indebted to Dr. Peter Ballmann for his suggestions and review of the current study, as well as for his advice concerning the study of avian evolution in general. I am grateful to Dr. Noel Boaz and all members of the ELNRP for giving me the opportunity to participate in the 2007

11 P103A, Pedal phalanx. Measurements: L: 20.36mm, PW: 8.30mm, PH: 7.74mm, DW: 6.56mm, DH: 6.58mm. This specimen is most likely the first pedal phalanx of the fourth toe of the left foot (Figure 7b and 7c).

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field expedition and for allowing me to study the avian material from the Sahabi Formation. Also I would like to thank Dr. Parissis Pavlakis for his support and advice during the field season and during the preparation of this study.

MAYR, G. and WEIDIG, I. (2004). The Early Eocene bird Gallinuloides wyomingensisâ&#x20AC;&#x201D; a stem group representative of Galliformes. Acta Palaeontologica Polonica 49 (2), 211â&#x20AC;&#x201C; 217. MILLER, A. H. (1966). An evaluation of the fossil anhingas of Australia. The Condor 68 (4), 315-320.

REFERENCES BALLMANN, P. (1987). A fossil bird fauna from the Pliocene Sahabi Formation of Libya. In: Neogene Paleontology and Geology of Sahabi (eds Boaz, N. T. et al.). New York, Liss, 113-117.

SHORT, L.L. (1969). A new genus and species of gooselike swan from the Pliocene of Nebraska. American Museum Novitates 2369, 1-7. VRBA, E.S. (1980). The significance of bovid remains as indicators of environment and predation patterns. In: Fossils in the Making; Vertebrate Taphonomy and Paleoecology (eds A. K. Behrensmeyer and A. P. Hill). Chicago, University of Chicago Press, 247- 271.

BAUMEL, J. J., KING, A. S., BREAZILE, J. E., EVANS H. E. and VANDEN BERGE, J. C. (eds.) (1993). Handbook of Avian Anatomy: Nomina Anatomica Avium, 2nd edition. Cambridge, Massachusetts, The Nuttall Ornithological Club, 23. BEHRENSMEYER , A.K. (1975). The taphonomy and paleoecology of PlioPleistocene vertebrate assemblages of Lake Rudolf, Kenya. Bulletin of the Museum of Comparative Zoology. 146 (10), 473-578.

WALKER, C. A. and DYKE, G. (2006).New records of fossil birds of prey from the Miocene of Kenya. Historical Biology 18 (2), 91-94.

B O A Z , N.T. (1996). Vertebrate palaeontology and terrestrial palaeoecology of As Sahabi and Sirt Basin. In: Geology of Sirt Basin (eds M. J. Salem, A. J. Mouzughi and O. S. Hammuda), Amsterdam, Elsevier I, 531-539. MAYR, G., and CLARKE, J. (2003). The deep divergences of neornithine birds: A phylogenetic analysis of morphological characters. Cladistics 19, 527-553.

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Special Issue, No. 5

The Age of the Small Mammal Faunas from Jabal Zaltan, Libya WILMA WESSELS, OLDRICH FEJFAR, PABLO PELÁEZ-CAMPOMANES, ALBERT VAN DER MEULEN, HANS DE BRUIJN, and ALI EL-ARNAUTI

ABSTRACT On the basis of the evolutionary stage of the small mammal species and the faunal compositions we assign three Jabal Zaltan assemblages to the middle Early Miocene (18-19 ma) — one to the late Early Miocene (16-17 ma) and two to the Middle Miocene (14-15 ma) — in total covering approximately 4 million years.

Wilma Wessels, Utrecht University, Faculty of Earth Sciences, Department of Geology, P.O. Box 80021, 3508 TA Utrecht, The Netherlands, wessels@geo.uu.nl Oldrich Fejfar, Charles University, Faculty of Science Department of Paleontology, Albertov 6, Praha 2, CZ-12843, Czech Republic, Fejfar@prfdec.natur.cuni.cz Pablo Peláez-Campomanes, Museo Nacional de Ciencas Naturales, c/ Jose Gutierrez Abascal 2, 28006 Madrid, Spain, mcnp177@mncn.csic.es Hans de Bruijn, Utrecht University, Faculty of Earth Sciences, Department of Geology, P.O. Box 80021, 3508 TA Utrecht, The Netherlands, hdbruijn@geo.uu.nl Albert Van Der Meulen, Utrecht University, Faculty of Earth Sciences, Department of Geology, P.O. Box 80021, 3508 TA Utrecht, The Netherlands, avermeul@geo.uu.nl Ali El-Arnauti, Department of Earth Sciences, Faculty of Science, Garyounis University, Benghazi Libya, alielarnauti@yahoo.com

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INTRODUCTION

Outcrops of marine sediments (marls and fine sands) with â&#x20AC;&#x153;sand dollarsâ&#x20AC;? and crab fragments occur southwest from where the road crosses the plateau. In a southerly direction (for several km) continental sediments interfinger with shallow marine sediments. The former become more dominant towards the south (southeast), where the sand component in the sediments increases rapidly. The layering of the sediments is overall horizontal. During the 1997 expedition three to four fossiliferous units (sandstones) were

Two geological/paleontological field campaigns in 1983 and in 1997 in the Jabal Zaltan area of Libya (see Boaz, et al., this volume), investigated the fluviatile sediments of the Marada Formation (see Hawat, this volume). Both expeditions prospected the north-south-trending escarpment of fluviatile sediments to the south of the Zaltan Oasis (Figure 1). The small mammal associations collected during both expeditions were described and discussed in Wessels et al. (2003).

Figure 1. Geographical map with the Jabal Zaltan localities containing small mammal remains (modified after Savage and Hamilton, 1973). 130

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The second unit (suffix B), mostly channel deposits, consists of coarse green sands with many large bones and greenish silty layers. Locality ATH4B yielded some identifiable small mammal remains. The third unit (suffix C) consists mostly of white (bleached) sands intersected by small pebble layers. Bioturbation and large bones are common. In locality QAB1C only three specimens of rodents were found. The fourth unit (suffix D) is composed of coarse sands with large bones. Small mammal remains have not been found in these sediments. In 1997 the two localities of 1983, MS2 and Wádí Shatírát, were not relocated or re-collected. In total, seven localities yielded remains of identifiable small mammals. Although only 48 fossil teeth were recovered, the diversity they represent is large: 12 species representing seven rodent families, one lagomorph family and one bat family. The reconstructed stratigraphic sequence of the Jabal Zaltan localities (Table 1) is based on the litho- and biostratigraphic position of the 1997 localities and the faunal content of localities MS2 and Wádí Shatírát (1983 expedition).

recognised at several places along the escarpment. In detail, the sedimentation is discontinuous, but from a distance it seems that layers are continuous due to the presence of “iron-banded” sediments (erosional levels, or due to weathering). These levels probably represent hiatuses in sedimentation and are interpreted as strongly diachronous levels. Therefore, precise correlation of fossiliferous levels between the outcrops is difficult. The correlation of the localities in different sections is therefore mainly based on fossil content. Although fossil wood (palm) occurs along the whole escarpment, it is most abundant in the transition zone between the marine and continental sediments (Figure 2). All fossil logs are horizontally positioned and have been transported. Long tree trunks up to 5 m are not scarce. The fossil vertebrates are distributed throughout the whole Marada Formation. Large accumulations are absent, bone and teeth have, after transport over some distance, accumulated in low concentrations. Most of the vertebrate remains are disarticulated bones, fragments of bone, or isolated teeth. However, skulls of mammals have been found, indicating a short period or distance of transport. The remnants of the small mammals were found in so-called “blow-out holes”, or in foresets. The lowermost fossiliferous unit (suffix A in locality name) consists of shallow channel deposits containing rustcoloured sands, small clay lenses, reworked clay pebbles, remnants of bioturbation, wood (stumps) and large mammal bones. In localities ATH5A1, ATH7A2 and ATH7A3 small identifiable mammal remains were recovered.

AGE DETERMINATION OF THE LOCALITIES In locality ATH7A2 the remains of two rodent species were found: Thryonomyidae nov. gen. et nov. sp. and Prokanisamys sp. The Thryonomyidae from Jabal Zaltan seem to be more closely related to Late Eocene phiomyids from Algeria (Jaeger, et al., 1985), than to the Oligocene forms of 131

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Figure 2. â&#x20AC;&#x153;Fossil forestâ&#x20AC;? near Bir Zaltan. (Photo Remmert Daams, 1997).

In locality ATH7A3 the rodent Thryonomyidae nov. gen. et nov. sp. and the ochotonid Austrolagomys sp. are present. In 2003 we assigned these specimens to ?Kenyalagomys sp. However, Kenyalagomys MacInnes 1957 is considered to be a junior synonym of Austrolagomys Stromer 1926 by Mein and Pickford (2003). The ochotonid is very similar, but smaller than A. minor (MacInnes, 1957) from Rusinga which is dated at 18 ma (Lavocat, 1973). The presence in our locality of a smaller Austrolagomys species is considered to be indicative of an Early Miocene age. Based on the affinities of the species in this locality we date this association as older than 18 ma. In locality ATH5A1 the rodents Cricetidae gen. et sp. indet. and Prokanisamys sp. are represented. The

Libya and Egypt and the Miocene phiomyids and Thryonomyidae from eastern Africa (Lavocat, 1973; Denys, 1992; Winkler, 1992). Prokanisamys sp. is close in morphology to Prokanisamys major Wessels and De Bruijn 2001 known from Pakistani assemblages dated between 19.5 and 16.4 ma (Wessels and De Bruijn, 2001). It is similar to the Early Miocene taxa from Pakistan and not to the Middle Miocene forms. Therefore, the immigration of the Rhizomyinae into North Africa must have taken place during Early Miocene times. Prokanisamys sp. is considered to be ancestral to Pronakalimys andrewsi Tong and Jaeger 1993 from Fort Ternan (14 ma). On the basis of the affinities of the Prokanisamys species in this locality we date this association as younger than 19 ma and older than 16 ma. 132

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Figure 3. â&#x20AC;&#x153;Blow-outâ&#x20AC;? level, locality ATH5A1. (Photo Remmert Daams, 1997).

Figure 4. Unit A, Locality ATH7A2, channel deposits, rust-coloured sands with larger bones (including ray, shark, and crocodile). (Photo Remmert Daams, 1997).

Figure 5. Unit B, Locality ATH3B, channel deposits with coarse green sands and green silty layers. (Photo Remmert Daams, 1997).

cricetid resembles African as well as Eurasian Oligocene cricetids, but its taxonomical position remains unclear. The locality ATH4B contains the rodents Mellalomys sp., cf. Myocricetodon sp., Prokanisamys sp., Sayimys nov. sp. and Thryonomyidae nov. gen. et nov. sp.

The origin and migration pattern of the Myocricetodontinae are not yet fully understood, but primitive Myocricetodontinae are known from the Lower Miocene (MN3) of Turkey (Wessels, et al., 2002) and other, more derived, Myocricetodontinae are known from 133

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Figure 6. Unit C, locality QAB4C, white-coloured silt overlain by light brown-greenish fine sand containing bone (Photo Remmert Daams, 1997).

Horáčcek, Fejfar and Hulva 2006 are recognised. Potwarmus sp. seems to be slightly more evolved than the other two species of the genus (Potwarmus primitivus (Wessels, De Bruijn, Hussain, and Leinders, 1982) and Potwarmus thailandicus (Jaeger, Tong, Buffetaut, and Ingavat, 1985). The occurrence of Potwarmus sp. in northern Africa indicates a migration of this genus from southern Asia into Africa. Its migration route is unknown since primitive murines are not known from Asia Minor and the Arabian peninsula. Potwarmus sp. is slightly more evolved than the Potwarmus species from Banda daud Shah in Pakistan (dated ca. 16 ma; Wessels, et al., 1982), excluding a migration during the Early Miocene times. Heterosminthus sp. is the oldest occurrence known so far of a Lophocricetodontine species in Africa. It resembles Heterosminthus Schaub 1930 (known from the Late Oligocene and the Miocene of Asia (Daxner-Höck, 2001)), and seems less evolved than Arabosminthus Whybrow, Collinson, Daams, Gentry, and McClure 1982 (Early–Middle Miocene of

Pakistan (18-13.7 ma), Turkey (13-11 ma) and Saudi Arabia (16 ma) (Wessels et al., 1982; Wessels, 1996; Wessels, 1998). The Myocricetodon and Mellalomys species from Jabal Zaltan are more primitive than those from Beni Mellal (14 ma) and Berg Aukas (13 ma). The Jabal Zaltan assemblages are, therefore, considered to be older than these localities. The ctenodactylid molars show characteristics as in Sayimys intermedius De Bruijn, Boon, and Hussain 1989 from the Middle Miocene of Pakistan (De Bruijn, et al., 1989). It is primitive in comparison to Africanomys pulcher Lavocat 1961 (in Jaeger, 1971) and is regarded as its predecessor. Sayimys seems to have entered Africa at about the same time as the Myocricetodontinae or earlier. On the basis of the affinities of the species in this locality we date this association as older than 16 ma. In locality MS2 the rodents ? Cricetidae gen. et sp. indet., Potwarmus sp., Mellalomys sp., Heterosminthus sp. indet., Sayimys nov. sp., the ochotonid Alloptox sp., and the bat Scotophilisus libycus 134

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Saudi Arabia). The vespertilionid bat, Scotophilisis libycus, is morphologically close to extant Scotophilus species from Southeast Asia and sub-Saharan Africa and is regarded as a member of a stemline of Scotophilus Leach 1821. Fossil members of Scotophilus are

otherwise only known from western Europe, from Anwil and Steinheim, younger than 13 ma (Engesser, 1972). The ochotonid specimen shows a close resemblance to Alloptox anatoliensis Ünay and Sen 1975 from the Middle Miocene of Turkey. On the basis of the affinities

Table 1. Localities and Species List Locality

(Sub)Family

Species

Wádí Shatírát

Murinae Ctenodactylidae

Potwarmus sp. Sayimys nov. sp.

MS2

Cricetidae Murinae Myocricetodontinae Lophocricetinae Ctenodactylidae Ochotonidae Vespertilionidae

?Cricetidae gen. et sp. indet. Potwarmus sp. Mellalomys sp. Heterosminthus sp. indet. Sayimys nov. sp. Alloptox sp. Scotophilisis libycus

QAB1C

Myocricetodontinae

Mellalomys sp.

ATH4B

Myocricetodontinae Myocricetodontinae Rhizomyinae Ctenodactylidae Thryonomyidae

Mellalomys sp. cf. Myocricetodon sp. Prokanisamys sp. Sayimys nov. sp. Thryonomyidae nov. gen. et nov. sp.

ATH5A1

Cricetidae Rhizomyinae

Cricetidae gen. et sp. indet. Prokanisamys sp.

ATH7A3

Thryonomyidae Ochotonidae

Thryonomyidae nov. gen. et nov. sp. Austrolagomys sp.

ATH7A2

Rhizomyinae Thryonomyidae

Prokanisamys sp. Thryonomyidae nov. gen. et nov. sp. 135

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interpretation of Potwarmus is correct (younger than 16 ma), Potwarmus migrated into Africa during the Middle Miocene, perhaps during the period when Griphopithecus, Alloptox, and Heterosminthus migrated into Anatolia and central Europe (Rögl, 1999).

of the species, especially of Potwarmus in this locality, we date this association as younger than 16 ma. On the basis of the faunal content we conclude that these Jabal Zaltan assemblages represent three periods in time and cover approximately 4 million years. The localities ATH7A2, ATH7A3 and ATH5A1 belong to the middle Early Miocene, locality ATH54B to the upper part of the Early Miocene, and localities MS2 and Wádí Shatírát to the lower part of the Middle Miocene.

ACKNOWLEDGEMENTS We thank Sirt Oil Company and its Chairman, Management Committee Ali El Sogher for arranging the facilities for fieldwork and assistance in accommodation and transport. AGOCO and its former President, Farag Said, are thanked for supporting the project by facilitating travel to Libya and ordering sieves and other equipment. Dr. Helmut Mayr was a member of the team and contributed to the fieldwork. The late Dr. Remmert Daams and the late Dr. Dolores Soria were highly appreciated members of the 1997 expedition. The first author acknowledges Drs. Noel Boaz and Paris Pavlakis for the possibility to present these results at the conference “Euro-African Biotic Evolution in the Neogene” (Athens, 2006).

CONCLUSIONS The small mammal faunas of the Jabal Zaltan localities span approximately 4 million years, from 19 ma to 15 ma. Differences between the assemblages appear substantial enough to show that at least three different intervals are represented by the small mammal associations of Jabal Zaltan. The closure of the Tethys Sea in the Early Miocene presumably enabled exchange of land mammal faunas between Eurasia and Africa. During the earliest part of the Early Miocene faunal exchange is recorded between Africa and Eurasia. Two main migration waves have been recognised during the Early Miocene, one around 19 ma and another around 16-17 ma (Thomas, 1985; Rögl, 1999). Ochotonidae, primitive cricetids, sciurids, and rhizomyines migrated into Africa during the first period of faunal exchange. The Myocricetodontinae (and perhaps the Ctenodactylidae) were part of the second migration wave, but this migration was limited to northern Africa. If our age

REFERENCES DAXNER- HÖCK, G. (2001). New Zapodids from Oligocene-Miocene deposits in Mongolia. Part I. Senckenbergiana Lethaea 81 (2), 359-389. BRUIJN, H., BOON, E. and HUSSAIN, S.T. (1989). Evolutionary trends in Sayimys (Ctenodactylidae, Rodentia) from the lower Manchar Formation (Sind, Pakistan). Proceedings Koninklijke Nederlandse Akademie van Wetenschappen B 92, 191214. DE

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D ENYS , C. (1992). Présence de Saccostomus (Rodentia, Mammalia) à Olduvai Bed I (Tanzanie, Pléistocène Inférieur). Implications phylétiques et paléobiogéographiques. Geobios 25, 145154.

inférieur. Ecole Practique des Hautes Etudes (3ème Section) Mémoires et Travaux de l’ Institute de Montpellier 1, 1248. LEACH, W.E. (1821). The characters of three new genera of bats without foliaceous appendages to the nose. Transactions of the Linnean Society of London 13, 69-72.

ENGESSER, B. (1972). Die obermiozäne Säugetierfauna von Anwil (Baselland). Tätigkeit Naturforschungs Gesellschaft Baselland 28, 37-363.

MACINNES, D.G. (1953). The Miocene and Pleistocene Lagomorpha of East Africa. In: Fossil Mammals of Africa. British Museum of Natural History 6, 30 p.

HORÁČEK, I. FEJFAR, O. and HULVA, P. (2006). A new genus of vespertilionid bat from Early Miocene of Jabal Zaltan, Libya, with comments on Scotophilus and early history of vespertilionid bats (Chiroptera). Lynx (Praha) n.s. 37, 131-150.

MEIN, P., AND PICKFORD, M. (2003). Fossil picas (Ochotonidae, Lagomorpha, Mammalia) from the basal Middle Miocene of Arrisdrift, Namibia. Memoir of the Geological Survey Namibia 19, 171-176.

JAEGER, J.-J. (1971). Un cténodactiylidé (Mammalia, Rodentia) nouveau, Irhoudia bohlini n.g.n.sp. du Pléistocène inférieur du Maroc, rapports avec les formes actuelles et fossiles. Notes de Service Géologique Marocain 31(237), 113-140.

RÖGL, F. (1999). Circum-Mediterranean paleogeography. In: The Miocene Land Mammals of Europe (eds G.E. Rössner and K. Heissig). München, Verlag Dr. Friedrich Pfeill, 39-48.

JAEGER, J.-J., TONG, H., BUFFETAUT, E. and INGAVAT, R. (1985). The first fossil rodents from the Miocene of northern Thailand and their bearing on the problem of the origin of the Muridae. Revue de Paleobiologie 4(1), 1-7.

SAVAGE, R.J.G and HAMILTON, W.R. (1973). Introduction to the Miocene mammal faunas of Gebel Zelten, Libya. Bulletin of the British Museum, Natural History, Geology Series 22(8), 515-527.

LAVOCAT, R. (1961). Le gisement de vertébrés Miocènes de Beni-Mellal (Maroc). Etude systématique de la faune de mammifères et conclusions générales. Notes et Mémoires du service Géologique du Maroc 155, 29-94, 109-144.

SCHAUB, S. (1930). Quartäre und Jungtertiäre Hamster. Abhandlungen des Schweizerischen Paläontologische Gesellschaft (Mémoires de la Société paléontologique Suisse) 49, 1-49. STROMER, E. (1926). Reste Land- und Süsswasser-bewohnender Wirbeltiere aus den Diamantenfeldern Deutsch-

LAVOCAT, R. (1973). Les rongeurs du Miocène d'Afrique orientale. I Miocène

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THOMAS, H. (1985). The Early and Middle Miocene land connection of the AfroArabian plateau and Asia: A major event of hominoid dispersal? In: Ancestors: The Hard Evidence (ed E. Delson). New York, Liss, 42-50.

WESSELS, W., THEOCHOROPOULOS, K.D., DE BRUIJN, H. and ÜNAY, E. (2002). Myocriceto-dontinae and Megacricetodontini (Rodentia) from the Lower Miocene of NW Anatolia. Lynx (Praha) n.s. 32, 371-388.

TONG, H. and JAEGER, J.-J. (1993). Muroid rodents from the Middle Miocene Fort Ternan locality (Kenya) and their contribution to the phylogeny of muroids. Palaeontographica, Abteilung A: Palaeozoologie-Stratigraphie 229(1-3), 5173.

WESSELS, W. ÜNAY, E. and TOBIEN, H. (1987). Correlation of some Miocene faunas from northern Africa, Turkey and Pakistan by means of Myocricetodontidae. Proceedings Koninklijke Nederlandse Akademie van Wetenschappen B90(1), 6582.

ÜNAY, E. and SEN, S. (1975). Une nouvelle e s p e c e d 'A l l o p t o x ( L a g o m o r p h a , Mammalia) dans le Tortonien de l'Anatolie. Bulletin of the Mineral Research and Exploration Institute of Turkey 85, 145-152.

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WESSELS, W. (1996). Myocricetodontinae from the Miocene of Pakistan. Proceedings Koninklijke Nederlandse Akademie van Wetenschappen 99 (3-4), 253-312. WESSELS, W. (1998). Gerbillidae from the Miocene of Europe. Mitteilungen der Bayerischen Staatssammlung für Paläontologie und Historische Geologie 38, 187-207.

WHYBROW, P.J., COLLINSON, M.E., DAAMS, R., GENTRY, A.W. and MCCLURE, H.A. (1982). Geology, fauna (Bovidae, Rodentia) and flora of the early Miocene of eastern Saudi Arabia. Tertiary Research 4 (3), 105-120.

WESSELS, W. and DE BRUIJN, H. (2001). Rhizomyidae from the lower Manchar Formation (Miocene, Pakistan). Annals of Carnegie Museum 70(2), 143-168. WESSELS, W., DE BRUIJN, H., HUSSAIN, S.T. and LEINDERS, J.J.M. (1982). Fossil rodents from the Chinji Formation, Banda

WINKLER, A.J. (1992). Systematics and biogeography of Middle Miocene rodents from the Muruyur Beds, Baringo District, Kenya. Journal of Vertebrate Paleontology 12 (2), 236-249.

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New Data on the Rodent Fauna from As Sahabi, Libya JORDI AGUSTĂ?

ABSTRACT

New fieldwork undertaken under the auspices of the E.L.N.R.P. at As Sahabi in the year 1998 by a joint team of Garyounis University, Benghazi and the Institute of Palaeontology M. Crusafont of Sabadell, Spain included sieving of more than 10 tons of sediments from locality P61. This work yielded remains of the species Abudhabia yardangi (Munthe), Myocricetodon sp., Progonomys aff. mauretanicus, Irhoudia sp., and Cercopithecini indet. The composition of the fauna strongly suggests a pre-Pliocene and even a Turolian, pre-Messinian Salinity Crisis, age. Palaeontological surface survey also yielded a rich diversity of large vertebrates, including crocodiles and large herbivores (equids and artiodactyls).

Jordi AgustĂ, ICREA-Institute of Human Paleoecology, University Rovira Virgili, Pl. Imperial Tarraco, 1. 43005- Tarragona, Spain, jordi.agusti@icrea.es

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1987). As happened with other Late Miocene-Early Pliocene Tatera-like gerbils described outside Africa (Protatera kabulense Sen and Protatera almenarensis Agusti), it was included in the genus Protatera Jaeger. The type-species is Protatera algeriensis from the locality of Amama-2, Algeria. Since then, the systematics of this group has been enriched with the description of two new genera, Abudhabia de Bruijn and Whybrow and Debruijnimys Agusti and Castillo, which raises again the question of the generic assignment of the As Sahabi gerbil. The species from As Sahabi differs from Abudhabia baynunensis only in the presence of a longitudinal ridge connecting the anteroconid to the protoconid and the metaconid (a character which can be barely recognised in the figure by Munthe, 1987; see Table 1). In this way, it resembles Debruijnimys julii Agusti and Castillo from the earliest Pliocene of Spain. The sharing of this derived character with the Early Pliocene Spanish gerbils suggests that at this time, the northern Africa gerbils had already diverged from the Asian lineage and formed a separate lineage. This northern African lineage probably settled on the Iberian Peninsula during the Messinian Salinity Crisis. However, Debruijnimys julii is significantly larger and presents a clearly derived morphology, including lower molars without posterolophids or labial anterolophids. In this respect, A. yardangi appears much closer to Abudhabia than to any other gerbil genus.

INTRODUCTION Since 1920 particularly through the discovery of a partial skeleton of the fourtusked mastodon Stegotetrabelodon syrticus Petrocchi 1941, the As Sahabi area became an increasingly important Neogene sequence. The area is situated in the northern part of the Sirt Basin, 100 km south of Ajdabiya, near the old fort called “Qasr as Sahabi.” Several, mostly Italian, geologists and palaeontologists studied the As Sahabi vertebrate fauna until the 1950’s. They considered it to be Middle to Late Miocene in age, based on comparisons with European sites (Petrocchi, 1952). From 1975 to 1981, the multidisciplinary International Sahabi Research Project made intensive investigations in the area (see Boaz et al., 1987). The new fieldwork developed as part of renewed research at As Sahabi (see Boaz et al, this volume) in the year 1998 by a joint team of the University of Garyounis, Benghazi and the Institute of Paleontology M. Crusafont (Sabadell, Spain). New vertebrate remains were discovered at existing fossil localities within the Sahabi Formation, and included crocodiles and large herbivores (equids and artiodactyls). Sieving of more than 10 tons of sediments from Locality P61 yielded the following faunal list of small mammals: Abudhabia yardangi (Munthe), Myocricetodon sp., Progonomys aff. maretaunicus Coiffait, and Irhoudia sp. Systematics Abudhabia yardangi (Munthe 1987) The most common rodent species in As Sahabi is Abudhabia yardangi (originally, Protatera yardangi Munthe

Myocricetodon sp. The Myocricetodon species present at As Sahabi is close in size and

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Table 1. Distribution of Characters in Selected Neogene Gerbils from Northern Africa and Western Eurasia. ++: frequent; +: present; (+): rare; - : absent.

A. baynunensis

A. yardangi

A. kabulensis

-(+)

P. algeriensis

-(+)

D. almenarensis -(+) -(+)

D. julii

D. davidi

+(-)

+/-

-(+)

-(+) -(+) -(+) -(+) -(+) +/-

-(+)

+(-)

-(+)

-(+) -(+) -(+)

-(+)

+/-

+/- -(+)

+(-)

+ +

Characters: 1. m1 anteroconid-protoconid connection 2. m1 protoconid-hypoconid connection 3. Posterolophid present in m1 4. Anterolophid present in m2 5. Posterolophid present in m2 6. m2 protoconid-hypoconid connection 7. Anterolophid present in m3 8. M1 anterocone-protocone connection 9. M1 protocone-hypocone connection 10. Anterolophe present in M2 11. M2 protocone-hypocone connection 12. M2 paracone-metacone connection 13. Reduced hypocone-metacone complex in the M3

morphology to M. seboui Jaeger and, certainly, has a less derived morphology than typical latest Miocene species such as M. jaegeri Benammi.

to the one which was described by Munthe (1987) as Progonomys sp. The presence of Progonomys cf. mauretaunicus in As Sahabi is very significant, indicating an age older than the first entry of European elements in the Maghrebian area during the Messinian Salinity Crisis.

Progonomys cf. mauretanicus Coiffait 1991 This species probably corresponds

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M. jaegeri also confirms a Miocene, even pre-Messinian, age for the As Sahabi fauna. This implies a considerable change in the correlations established for the whole Sahabi Formation and their associated gypsums. But, in that case, what is the age of the big canyons beneath As Sahabi? Would they be Tortonian in age? Also, this preliminary conclusion would oblige us to change our views of As Sahabi in relation to the zoogeography of Africa in Late Miocene times.

Irhoudia sp. The ctenodactylid from As Sahabi was originally referred as Sayimys sp. by Munthe (1987). Instead, the new material collected in the last field campaign indicates a closer relationship to Irhoudia, although retaining a primitive DP4 as in Africanomys. DISCUSSION The faunal list of rodents from P61 is somewhat different from that of Munthe (1987) and reveals aspects so far unknown from the age of the As Sahabi fauna. The most surprising result from the preliminary analysis of the small fauna from Sahabi P61 strongly suggests a pre-Pliocene and even, a Turolian, pre-Messinian Salinity Crisis age. According to the new material, Abudhabia yardangi closely fits A. baynunensis from the Late Miocene (Late Turolian?) Baynunah Formation (Emirate of Abu Dhabi, United Arab Emirates, de Bruijn and Whybrow, 1994). Although the anteroconid is connected to the protoconid in several specimens of A. yardangi (Table 1), suggesting a somewhat more advanced state than the Arabian species, the affinities between the two species strongly suggest a Late Miocene age for the As Sahabi Formation. This is also supported by the Late Miocene, terrestrial Messinian record of Spain, which shows the presence of typical North African rodents such as Debruijnimys almenarensis, certainly much more derived than Abudhabia yardangi from As Sahabi. The presence of a Myocricetodon species which is less derived than latest Miocene species such as

REFERENCES AGUSTÍ, J. (1990). The Miocene rodent succession in eastern Spain: A zoogeographical appraisal. In: European Neogene Mammal Chronology (eds. E. Lindsay, W. Fahlbusch and P. Mein). New York, Plenum Press, 375- 404. BOAZ, N.T., EL-ARNAUTI, A., GAZIRY, A.W., DE HEINZLEIN, J. and BOAZ, D.D. (eds) (1987). Neogene Paleontology and Geology of Sahabi, New York, Liss. BENAMMI, M. (2001). Découverte de deux nouvelles espèces du genre Myocricetodon dans le Miocène supérieur du bassin d´Aït Kandoula (Maroc). C. R. Acad. Sci. Paris, Sc. de la Terre 333, 187-193. BRUIJN, H. DE, and WHYBROW, P. (1994). A late Miocene rodent fauna from the Baynunah Formation, Emirate of Abu Dhabi, United Arab Emirates. Proc. Konink. Nederlande Akademie van Wetensch. 97 (4), 407-422.

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CASTILLO, C. and AGUSTÍ, J. (1996). Early Pliocene rodents (Mammalia) from Asta Regia (Jerez basin, Southwestern Spain). Proc. Konink. Nederlande Akademie van Wetensch. 99 (1-2), 25-43. JAEGER, J.J. (1977). Les rongeurs du Miocene moyen et supérieur du Maghreb. Palaeovertebrata, 8 (1): 1-166. MUNTHE, J. (1987). Small mammal fossils from the Pliocene Sahabi Formation of Libya. In: Neogene Paleontology and Geology of Sahabi (eds Boaz, N.T., ElArnauti, A., Gaziry, A.W., de Heinzelin, J. and Boaz, D.D.) New York, Liss, 135-144.. PETROCCHI, C. (1941). Il giacimento fossilifero di Sahabi. Bollettino della Societa Geologica Italiana 60, 107-114. PETROCCHI, C. (1952). Notizia generale sui giacimento fossilifero di Sahabi. Storia degli scavi - Resultati. Accad. Nazion. Quaranta, Roma 4 (3), 9-33.

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Peri-Messinian Dwarfing in Mediterranean Metaxytherium (Mammalia: Sirenia): Evidence of Habitat Degradation Related to the Messinian Salinity Crisis GIOVANNI BIANUCCI, GIUSEPPE CARONE, DARYL P. DOMNING, WALTER LANDINI, LORENZO ROOK, and SILVIA SORBI ABSTRACT One lineage of dugongid sirenians (Metaxytherium spp.) inhabited Old World waters throughout the Miocene and Pliocene. During the Early to Late Miocene (M. krahuletzi, M. medium) and the Early and Middle Pliocene (M. subapenninum), these animals were consistently large; however, the earliest Pliocene member of this lineage, M. serresii, was distinctly smaller, as shown by the population sample from Montpellier, France. In 1987 Domning and Thomas interpreted this as ecophenotypic dwarfing and attributed it to suboptimal foraging habitat in the wake of the Messinian Salinity Crisis (MSC). This explanation implied that the reduction in body size should have first occurred near the onset of the MSC, and should have been reversed after its end, or whenever adequate seagrass resources again became available. Recent discoveries of Late (post-M. medium) Miocene M. serresii in Calabria, Italy and the attribution to the latest Miocene of the M. serresii records from As Sahabi, Libya, previously referred to the Early Pliocene, support the hypothesis of peri-Messinian dwarfing. This decrease in size is well evidenced in this study where we have analysed the pattern of body size change from the Early Miocene to the Middle Pliocene of these and other diagnostic European and Libyan fossils of Metaxytherium. We have also observed an increase in tusk size of these sirenians beginning with M. serresii that could be related to a shift to a diet richer in rhizomes due to the degradation of food resources.

Giovanni Biannucci, Walter Landini, and Silvia Sorbi, Dip. Scienze della Terra, Univ. di Pisa,Via S. Maria, 53 56126 PI, Italy, bianucci@dst.unipi.it, landini@dst.unipi.it, sorbi@dst.unipi.it Giuseppe Carone, Gruppo Paleontologico Tropeano, Tropea, Via V. Veneto, 5 89861 Tropea (VV) Italy, p.carone@libero.it Daryl P. Domning, Department of Anatomy, Howard University, Washington, DC 20059 USA, ddomning@Howard.edu Lorenzo Rook, Dip. Scienze della Terra, University di Firenze, Via La Pira, 4 I-50121 FI, Italy, lrook@steno.geo.unifi.it

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pers. obs.), together with the attribution to the latest Miocene of the M. serresii records from As Sahabi, Libya, previously referred to the Early Pliocene (Boaz et al., 2008), support the hypothesis of peri-Messinian dwarfing. Testing this hypothesis, most of the diagnostic fossils of European and Libyan Metaxytherium held in various museum collections have been examined and measured by one of us (Domning, unpublished data). In no case, unfortunately, is a perfectly complete axial skeleton available to provide a precise measurement of body length. Therefore, other linear measurements must serve as proxies for body size; for example the total length of the mandible (measurement AB) and the breadth across occipital condyles (measurement ff'; ~ breadth across anterior cotyles of atlas). Measurement ffâ&#x20AC;&#x2122; is of particular interest, as it has recently been advocated as a proxy for body size in studies of fossil cetaceans (N. D. Pyenson and D. R. Lindberg, pers. comm., 2003). Since all the other dimensions examined (listed in Table 1) showed a similar pattern of change, and since skull measurement ff' and mandible measurement AB displayed this pattern as clearly as any and were available for several stratigraphic samples including the most critical Late Miocene samples, they were chosen to illustrate the entire data set. Fossil samples for which at least one of the dimensions could be used to characterise the body size of Metaxytherium at that locality are listed in Tables 2 and 3, together with our determinations of their geochronological ages; and the values of these dimensions are graphed against age of sample in Figure 1. Although it would be

INTRODUCTION The fossil genus Metaxytherium (Sirenia: Dugongidae: Halitheriinae) makes its appearance in the Old World in the Early Miocene, and persists until the Middle Pliocene as an single evolutionary lineage, currently divided into four chronospecies (Domning and Thomas, 1987). From the Middle Miocene onward, these species appear to have been the only sirenians surviving in Old World waters out of what had been a more diverse Paleogene sirenian fauna. In a revision of this lineage, Domning and Thomas (1987) noted a very slight morphological change in the Early and Middle Miocene species (M. krahuletzi and M. medium, respectively) followed by two conspicuous changes: an increase in tusk size (in the Lower Pliocene M. serresii and culminating in M. subapenninum), interpreted as adaptations to feeding on the rhizomes of the larger kinds of seagrasses (see Domning, 2001); and a reduction in overall body size in M. serresii, followed by a return in M. subapenninum to the original and even larger size, interpreted as ecophenotypic dwarfing attributed to suboptimal foraging habitat in the wake of the Messinian Salinity Crisis (MSC) (Domning, 1981; Domning and Thomas, 1987; Domning and Pervesler, 2001). This explanation implied that the reduction in body size should have first occurred near the onset of the MSC, and should have been reversed after its end, or whenever adequate seagrass resources again became available. The Pliocene record is consistent with this prediction, and the recent discoveries of Late (post-M. medium) Miocene M. serresii in Calabria, Italy (Carone and Domning,

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desirable to attach measures of statistical significance to these results, the small sample sizes presently available from most of the stratigraphic horizons (e.g., Table 4) preclude this, so we simply present these raw data as a preliminary indication of the apparent pattern in size change. In any case, the size differences we find are gross enough to be apparent despite the small statistical samples.

Table 1. Measurements compiled for comparisons. Letters in parentheses denote standardised measurements used in previous papers (e.g., Domning, 1988; Domning and Pervesler, 2001). SKULL Condylobasal length (AB) Breadth across exoccipitals (cc') Breadth across occipital condyles (ff'); approximately = breadth across anterior cotyles of atlas

RESULTS AND DISCUSSION

Breadth of cranium at frontoparietal suture (GG')

As far as could be determined from the (mostly) incomplete specimens available, all dimensions show a consistent pattern of body size change in Mediterranean Metaxytherium that appears to be one of gradual increase during the Miocene, subsequently accelerated and culminating in the Pliocene but abruptly interrupted by the peri-Messinian dwarfing. The body size changes in Old World Metaxytherium were grossly apparent from the few complete skulls available: an adult skull of M. medium from the Loire Valley 47 cm long, skulls of the Italian M. subapenninum about 52-60 cm long, skulls of M. serresii from Montpellier only 40-45 cm long; and by a few reconstructed skeletons: one of M. krahuletzi 3.25 m long (Domning and Pervesler, 2001); one of the Libyan M. serresii estimated about 2.3-2.4 m long (specimen 7P64A; Domning and Thomas, 1987). In Dusisiren jordani (Domning, 1978, Table 2), which may have had a smaller head/body ratio than Metaxytherium, a complete axial skeleton of an old adult with a skull 63 cm long had a total body length of 4.32 m. This suggests that M. subapenninum probably grew to lengths approaching 4 m.

Length, frontoparietal suture in midline to rear of external occipital protuberance (P) Minimum width of parietal roof at indentations formed by squamosals Height of supraoccipital (HSo) Width of supraoccipital (WSo) MANDIBLE Total length (AB) Height at coronoid process (CD) Height at condyle (DL) Minimum dorsoventral breadth of horizontal ramus (MO) TEETH Crown lengths of upper and lower molars - M2, M3 HUMERUS Maximum length, greater tubercle to distal end (AB) Length, saddle between head and greater tubercle to saddle of trochlea (QR) Maximum breadth, greater to lesser tubercle (CD) Maximum breadth, ectepicondyle to entepicondyle (EF) Maximum thickness, posterior side of head to anterior side of greater tubercle (GH)

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Table 2. Localities and dates of selected samples of EuroMediterranean Pliocene Metaxytherium (= “Felsinotherium”) spp. For type localities of nominal sirenian species, the names of the species described from there are given; species names in quotes are here considered junior synonyms. LOCALITY & REF.

STAGE/AGE

MAMM

AGE

HORIZON & REF.

PLIOCENE Brà (De Zigno, 1878: “F. gastaldi” )

Upper ZancleanLower Piacenzian

MN 15

3.1-3.8

Sabbie di Asti Formation (Ferrero and Pavia, 1996)

Montiglio (Bruno, 1839: M. subapenninum)

Upper ZancleanLower Piacenzian

MN 15

3.1-3.8

Sabbie di Asti Formation (Ferrero and Pavia, 1996)

Nizza Monferrato (Domning and Thomas, 1987)

Upper ZancleanLower Piacenzian

MN 15

3.1-3.8

Sabbie di Asti Formation (Ferrero and Pavia, 1996)

Nizza Monferrato (Pilleri, 1988)

Upper ZancleanLower Piacenzian

MN 15

3.1-3.8

Sabbie di Asti Formation (Ferrero and Pavia, 1996)

Riosto (Capellini, 1872:“F. forestii”)

Upper ZancleanLower Piacenzian

MN 15

3.3-3.9

Monte Adone Formation (Amorosi, et al., 2002)

S. Quirico d’Orcia (Fondi and Pacini, 1974)

Zanclean

MN 15

3.57-3.98

Upper portion of Globorotalia puncticulata Zone (Vaiani, pers. comm., 2006)

Case il Poggio, Val di Pugna (Capellini, 1872: “F. gervaisi”)

Zanclean

MN 14

3.9-4.2

Yellow sands (Bianucci, et al., 2001)

Rùffolo, Val di Pugna (Canocchi, 1987)

Zanclean

MN 14

3.9-4.2

Grey silty clay (Bianucci, et al., 2001)

Pilar de la Horadada, Alicante (Sendra, et al., 1999: M. serresii)

Zanclean

MN 14

3.57- 4.52 Globorotalia puncticulata Zone (Santisteban, pers. comm., 2006)

Deferrari Square, Genoa (Issel, 1910)

Zanclean

MN 14

4-5.1

Argille di Ortovero Fm (Giammarino and Tedeschi, 1980; Negri, et al., 1997)

Montpellier (Domning and Thomas, 1987: M. serresii)

Zanclean

MN 14

4-5.3 ?

Sables à Gryphaea virleti (Domning and Thomas, 1987)

Crude observations such as these gave rise to the hypothesis of peri-Messinian dwarfing. It was apparent, however, that adequate tests of this hypothesis would require denser stratigraphic sampling through the Old World Neogene, as well as larger fossil samples from each stratigraphic horizon. The present study only partially addresses this need; but so far as it goes, it corroborates the correlation of smaller sirenians with the peri-Messinian time interval. In fact the dwarf specimens are found just prior to and during, as well as just after, the Messinian Age. The earliest are those of the Cessaniti deposits (7.3-7.6 ma) (Carone and

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Table 3. Localities and dates of selected samples of Euro-Mediterranean Miocene Metaxytherium (= “Felsinotherium”) spp. For type localities of nominal sirenian species, the names of the species described from there are given; species names in quotes are here considered junior synonyms.

LOCALITY & REF.

STAGE/AGE

MAMMAL ZONE

AGE (ma)

HORIZON & REF.

UPPER MIOCENE As Sahabi (Domning & Thomas, 1987)

?Lower Messinian/upper Turolian

MN 13

ca. 6.8 ?

Lowermost Sahabi Formation (Mb. T) (Boaz, et al., 2008)

Cessaniti (Carone, 1997; Carone & Domning pers. obs)

Uppermost Tortonian

MN 12

7.3-7.6

Heterostegina deposits (Papazzoni & Sirotti, 1999)

S. Domenica di Ricàdi (Moncharmont Zei & Moncharmont, 1987)

Tortonian

MN 12-9

7.6-10.5

Yellow sandstone under the Heterostegina deposits (Nicotera, 1959)

Ponsano (Bianucci and Landini, 2003)

Lower Tortonian MN 12-9

8.14-10.5

Arenarie di Ponsano Formation (Foresi, et al., 1997)

Cisterna quarry (Bianucci, et al., 2003)

Lower Tortonian MN 12-9

8.14-10.5

Upper portion of “Pietra leccese” Formation (Mazzei, 1994)

Loire Valley (M. medium)

SerravallianTortonian; lower Vallesian

MN 9-7?

10-12.5 ?

(Ginsburg, et al., 1979)

Mannersdorf (M. sp.)

Badenian

MN 6-5

13-16

Leithakalk (R. Roetzel and P. Pervesler, pers. comm.., 1996)

Brest (M. sp.)

Langhian

MN 6-5?

15-16.4

(P. Janvier, pers. comm., 2001)

Olèrdola, Mas Romeu vell (Pilleri , et al., 1989: “M. catalaunicum”)

Upper BurdigalianLanghian

MN 6-5?

ca. 16-17 ?

(Pilleri, et al., 1989)

Manosque (Sorbi, pers. obs.: M. cf. krahuletzi)

Upper Burdigalian

MN 4

16.5-17.5

Molasse calcaire et sablomarneuse Formation (Wallez, et al., 1986)

Eggenburg area (Domning and Pervesler, 2001: M. krahuletzi)

Upper Eggenburgian; Burdigalian, Orleanian

MN 3 (lower ca. 20 part)

MIDDLE MIOCENE

LOWER MIOCENE

149

Burgschleinitz Formation (Domning and Pervesler, 2001)

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Figure 1. Scatterplots of measurements and ages of specimens in Tables 2 and 3. The stippled zone marks the Messinian Age (7.24-5.33 ma). The MSC itself extended from 5.96 to 5.32 ma. The dotted lines are drawn to represent our interpretation of the pattern of body size change in this lineage.

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a) data on width across occipital condyles (ff’1)

b) data on total length of mandible (AB) ff'

LOCALITY

SPECIMEN NO.

AGE (ma)

LOCALITY

(m m)

SPECIMEN NO.

AGE (ma)

M length

Case il Poggio

MUSNAF 4960

3.6

320

120

Riosto

MGPUB unnum.

3.6

370

4.0

145

S. Quirico d'Orcia

IGPS 213

3.8

415

MCNV unnum

4.2

102

Montpellier

NHMB MP 145

4.6

260

DSTG 2534atlas

4.5

119 As Sahabi

GUDGb 45P15A

6.8

178

As Sahabi*

GUDGb 7P64A

6.8

240

As Sahabi*

GUDGb 3P66A

6.8

240

Cessaniti

MBC 005

7.5

217

Cessaniti*

DSTC CMS 21

7.5

213

S. Domenica di Ricadi*

MPUN 18403

9.0

340

Bra

MC unnum.

3.5

147

Riosto

MGPUB unnum.

3.6

Ruffolo

IGF13747

Alicante Genoa Montpellier

NHMB MP 215

4.6

Montpellier

NHMB MP 994

4.6

Montpellier

FSM SM10

4.6

As Sahabi

GUDGb 69P66A

6.8

Cessaniti

GPT 30(ces)VM7

7.5

Cessaniti

GPT "Cranio C"

7.5

Cessaniti

MBC 37

7.5

100

Olèrdola

MV 1210

12.0

315

Loire

MNHN Fs2740

11.2

108

Manosque

MPNRL unnum.

17.0

302

Loire

MNHN Fs5001

11.2

119

Eggenburg*

KÜH 95/3

20.0

280

Mannersdorf

BLLM 22816

14.5

107

Léognan

MHNB unnum

20.5

238

Brest

LPB 16001

15.7

104

Olèrdola

MV 1210

16.5

Eggenburg

KME unnum.

20.0

100

Eggenburg

SON 95/109

20.0

105

Eggenburg

SON 95/51

20.0

102

Eggenburg

HMH unnum.

20.0

101

Eggenburg

HMH unnum.

20.0

Eggenburg

KÜH 87

20.0

Eggenburg

SON 96/41

20.0

108

Table 4. Data on a) width across occipital condyles (measurement ff’); b) total length of mandibles (AB); of Euro-Mediterranean Metaxytherium spp., used here as proxies for body size. * = estimated. Ages of localities are approximated as roughly the midpoints of the age ranges listed in Table 1. Measurements taken by Domning and Sorbi. Institutional abbreviations: BLLM, Burgenlandisches Landesmuseum, Eisenstadt, Austria; DSTC, Dipartimento di Scienze della Terra, Universita della Calabria, Cosenza, Italy; DSTG Museo Paleontologico dell’Università degli Studi di Genova, Italy; FSM, Faculté des Sciences, Montpellier, France; GPT, Gruppo Paleontologico Tropeano, Tropea, Italy; GUDGb, Garyounis University Department of Geology, Benghazi, Libya; HMH, Höbart-Museum, Horn, Austria; IGF, Museo di Geologia e Paleontologia dell’Università di Firenze, Italy; IGPS, Istituto di Geologia e Paleontologia dell’Università di Siena, Italy; KME, Krahuletz-Museum, Eggenburg, Austria; KÜH, collection from Kühnring, Austria in KME; LPB, Laboratoire de Paléontologie de Brest, France; MBC, Mario Bagnato private collection, Tropea, Italy; MC, Museo Craveri, Bra, Italy; MCNV, Museo de Ciencias Naturales de Valencia, Spain; MGPUB, Museo di Geologia e Paleontologia dell’Università di Bologna, Italy; MNHN, Musée National d'Histoire Naturelle, Paris, France; MHNB Musée d’Histoire Naturelle de Bordeaux, France; MPNRL, Maison du Parc naturel regional du Luberon, France; MPUN, Museo di Paleontologia dell’Università di Napoli, Italy; MUSNAF, Museo di Storia naturale, Accademia dei Fisiocritici, Siena, Italy; MV, Museu Vilafranca, Spain; NHMB, Naturhistorisches Museum, Basel, Switzerland; SON, collection from Sonndorf, Austria in Institut für Paläontologie, University of Vienna, Austria.

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especially as it is a component of the above hypothesis. The attainment of genetic maximum potential body size in mammals is critically dependent on sufficient quality and quantity of food. This is well documented in, for example, Pleistocene and Recent ungulates (Guthrie, 1984). Domning and Thomas (1987) attributed the dwarfing of M. serresii to the reduction in quality, quantity, and/or diversity of the sea-grass ecosystem in the wake of the MSC. Their prediction that the size decrease would appear with the onset of the MSC now appears to be confirmed, lending increased plausibility to the proposed (nutritional) cause. This scenario also appears plausible geologically. We must bear in mind that the MSC was not a single, sudden event, but came about gradually and in stepwise fashion over a long period. Repeated sea level, salinity, and temperature fluctuations of this sort, and their associated ecological disruptions, eventually culminated in the MSC (cf. Vidal et al., 2002, Fig. 7). Thus there would have been long and recurrent periods of significant ecological disturbance during which sea level, salinity, and other factors nevertheless oscillated close enough to normal marine conditions for sirenian populations to have survived. Complete desiccation of the Mediterranean, in contrast, would have killed off all sirenians and seagrasses there, and they would necessarily have had to recolonize the Mediterranean Basin after the Messinian. However, some evidence indicates nearnormal marine conditions somewhere in the basin during parts of the Messinian; e.g., the early Messinian Sahabi Formation deposits (Boaz, et al., 2008) and the latest Messinian â&#x20AC;&#x153;Lago-Mareâ&#x20AC;? event (Carnevale,

Domning, pers. obs.), followed by those of As Sahabi deposits previously referred to the Early Pliocene and now attributed to the latest Miocene, about 6.8 ma (Boaz, et al., 2008), while the third are those of the Lower Pliocene deposits of Montpellier (4.0-5.3 ma) (Domning and Thomas, 1987). Possible causes for this correlation include climatic change and geographic restriction as well as nutritional limitations. As for climate change, the Mediterranean region (like the Earth in general) was undergoing a net cooling during the Late Miocene and Pliocene (Zachos et al., 2001). Sirenians, with their low metabolic rates, would be expected to adapt to cooler climate by an increase in body size, not a decrease. So the long-term climatic cooling could be involved, if anything, in the overall size increase in the Old World Metaxytherium lineage â&#x20AC;&#x201C; as with the hydrodamaline sirenians in the North Pacific (Domning, 1978). Although Hydrodamalis survived into historic times, the Mediterranean Metaxytherium did not, and their extinction during the Middle Pliocene is most logically explained by the acceleration of climatic cooling after 3 ma (Capozzi and Picotti, 2003), independently of whatever cause(s) may be adduced for the preceding changes in body size. Geographic restriction can cause dwarfism, as seen in dwarf elephants on islands (Roth, 1990). This phenomenon is thought to be due to the limited area and/or resources of islands, and/or the absence of large predators. In the course of the MSC, the Mediterranean Sea would have been broken up into smaller (and resource-poor) basins and these could be thought of as analogous to terrestrial islands. Nutritional stress in itself appears more promising as an explanation, 152

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seagrasses of all sizes (Domning, 2001). If the onset(s) of the MSC did away with the dominant Posidonia, leaving more eurybiontic species such as C. nodosa to provide the bulk of a reduced total biomass, then the sirenians may have had to shift to a diet richer in rhizomes, especially the newly dominant medium-sized ones. The predicted result (following the model of Domning, 2001) would be an increase in tusk size to the “medium” dimensions observed in M. serresii. Post-Messinian recolonisation of the Mediterranean by Posidonia, and re-establishment of its dominance, might have led the sirenians to adapt to eating its rhizomes, rather than returning to their less challenging midMiocene diet of smaller species, because by then the climate had cooled further and the larger rhizomes might have provided a greater energy yield. The predicted result: still larger tusks, as seen in M. subapenninum.

et al., 2006). As yet we have no sirenian samples corresponding to the latter episode, but any such sirenians would presumably have been dwarfed as well, and would not alter our present conclusions. This scenario also suggests an explanation for the increase in tusk size that began with peri-Messinian Metaxytherium. Today, the dominant Mediterranean seagrass in terms of biomass, Posidonia oceanica, is a climax species having “large” rhizomes in the sense of Domning (2001) (i.e., up to 1 cm in diameter). However, it is very sensitive to changes in salinity or temperature. This was probably also true in the Miocene, since seagrasses and their ecology appear to have taken on their modern forms even earlier (Domning, 1981, 2001). Consequently, P. oceanica should have been among the first seagrasses to succumb to the disruptions of the imminent salinity crises. It would presumably have yielded its dominance to smaller seagrasses such as Cymodocea nodosa, a eurybiontic “pioneer” species with rhizomes of “medium” size (about 2-3 mm), and Zostera marina, also very eurybiontic, with rhizomes 2-5 mm in diameter (den Hartog, 1970; Phillips and Meñez, 1988). Although the Miocene Mediterranean seagrass flora was likely more diverse than today’s, both Posidonia sp. and Cymodocea nodosa were surely present, as they are both reported from the Eocene of the Paris Basin (den Hartog, 1970; Phillips and Meñez, 1988). Leaves of seagrasses referred to Posidonia oceanica are also found above the Messinian gypsum bed of the Piedmont basin (Sturani, 1976:18, Fig. 5c). Small-tusked Metaxytherium (such as M. medium) are hypothesized to have fed on small and medium-sized rhizomes (not as large as Posidonia), as well as leaves of

CONCLUSIONS The measurements of the most diagnostic fossils of European and Libyan Metaxytherium, taken to test the hypothesis of peri-Messinian dwarfing, show an overall pattern of body size change that appears to be a gradual increase during the Miocene, accelerated and culminating in the Pliocene probably in response to long-term climatic cooling. This trend is abruptly interrupted by the peri-Messinian dwarfing. This dwarfing is now better supported by three records (two just before and one just after the MSC) and is interpreted as ecophenotypic dwarfing coincident with the MSC, attributed to the degradation of the near-shore habitat and food resources on which these animals 153

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AMOROSI, A., SCARPONI, D. and RICCI LUCCHI, F. (2002). Palaeoenvironmental changes in the Pliocene Intra-Apenninic Basin, near Bologna (northern Italy).Geobios, Mémoire Spécial 24, 7-18.

depended. This degradation could also explain the increase in tusk size that began with peri-Messinian Metaxytherium. Sirenians may have had to shift to a diet richer in rhizomes, especially the newly dominant medium-sized ones. The post-Messinian reestablishment of the dominance of Posidonia might have led the sirenians to adapt to eating its rhizomes, rather than returning to their less challenging midMiocene diet of smaller species, because by then the climate had cooled further and the larger rhizomes might have provided a greater energy yield.

BERNOR, R.L. and SCOTT, R.S. (2003). New interpretations of the systematics, biogeography and paleoecology of the Sahabi hipparions (latest Miocene) (Libya). Geodiversitas 25(2), 297-319. BIANUCCI, G. and LANDINI, W. (2003). Metaxytherium medium (Mammalia: Sirenia) from Upper Miocene sediments of the Arenaria di Ponsano Formation (Tuscany, Italy). Rivista Italiana di Paleontologia e Stratigrafia 109(3), 567573.

ACKNOWLEDGEMENTS We are very grateful to the directors and staff of all the museums from which specimens are cited here. Sorbi thanks the organizers of the “Euro-African Biotic Evolution in the Neogene, Research Conference and Workshop” (Athens, November 2006) for their warm hospitality. Domning thanks the organizers of the Geology of East Libya Symposium (Benghazi, November 2004) for generously supporting his attendance at the symposium as well as a research visit to Italy directly contributing to this paper. He also thanks the Gruppo Paleontologico Tropeano, Tropea, Italy, for their warm hospitality and enthusiastic support of this research.

BIANUCCI, G., CASCELLA, A., MAZZA, P., MEROLA, D. and SARTI, G. (2001). The Early Pliocene mammal assemblage of Val di Pugna (Tuscany, Italy) in the light of calcareous plankton biostratigraphical data and paleoecological observations. Rivista Italiana di Paleontologia e Stratigrafia 107 (3), 425-438. BIANUCCI, G., LANDINI, W. and VAROLA, A. (2003). New records of Metaxytherium (Mammalia: Sirenia) from the late Miocene of Cisterna quarry (Apulia, southern Italy). Bolletino della Società Paleontologica Italiana 42 (1-2), 59-63. BLANC-VALLERON, M.-M., PIERRE, C., CAULET, J.P., CARUSO, A., ROUCHY, J.-M., CESPUGLIO, G., SPROVIERI, R., PESTREA, S. and DI STEFANO, E. (2002). Sedimentary, stable isotope and micropaleontological records of paleoceanographic change in the Messinian Tripoli Formation (Sicily, Italy).

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Special Issue, No. 5

Revisiting As Sahabi Equid Species Diversity, Biogeographic Patterns, and Dietary Preferences RAYMOND L. BERNOR, THOMAS M. KAISER, and DOMINIK WOLF

ABSTRACT Four taxa of hipparionine equids are tentatively distinguished in the As Sahabi assemblage: Cremohipparion aff. matthewi, Cremohipparion nikosi (= periafricanum), cf. Hipparion s.s., and “Sivalhippus” sp. Based on the equids a biostratigraphic age attribution to early MN13, circa 6.5 ma, is made. There are biogeographic relationships with the eastern Mediterranean Greek and Iranian faunas, signaled by the presence of two species of Cremohipparion and Hipparion s.s., and with a South Asian-East African corridor that shared members of the “Sivalhippus” Complex. Enamel mesowear analysis of 30 As Sahabi equids indicates that they consistently classify in the grazer spectrum of the mesowear continuum and record a marked shift to seasonal, open-country habitats in the Late Miocene of northern Africa.

Raymond L. Bernor, National Science Foundation, GEO/EAR: Sedimentary Geology and Paleobiology Program, Arlington, VA 22230; College of Medicine, Department of Anatomy, Laboratory of Evolutionary Biology, Howard University, 520 W St. N.W., Washington D.C. 20059, USA, rbernor@howard.edu and rbernor@comcast.net Thomas M. Kaiser, Biozentrum Grindel und Zoologisches Museum, University Hamburg, D-20146 Hamburg, Germany, thomas.kaiser@uni-hamburg.de Dominik Wolf, College of Medicine, Department of Anatomy, Laboratory of Evolutionary Biology, Howard University, 520 W St. N.W., Washington D.C. 20059, d_wolf_palaeo@yahoo.de

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that a reevaluation of As Sahabi hipparion systematics and biogeographic relationships was needed. This reevaluation requires extensive analysis and comparison of both dental and postcranial evidence. Bernor and Scott (2003) reevaluated the postcranial evidence as represented by metapodial and phalangeal elements, while the dental record is currently being reevaluated by us. Bernor and Scott (2003) found evidence for at least two hipparion species in the As Sahabi fauna which they referred to “Cremohipparion” aff. matthewi and “Hipparion” (Sivalhippus) sp. “Cremohipparion” aff. matthewi is represented by elongate-slender metapodials and compares most closely to Cremohipparion matthewi represented from the late MN12 quarries at Samos (Greece) and the MN13 locality of Maramena (Greece). Cremohipparion is a lineage of late Vallesian to late Turolian age (9.7 – 5.3 ma) that likely arose in the easternMediterranean – Southwest Asian Subparatethyan Province and extended its range into East and South Asia as well as North Africa. One radicle of Cremohipparion, including Cremohipparion matthewi, underwent progressive size reduction with accompanying evolution of elongate and slender limbs adapted for cursorial behavior. There is growing evidence of cladogenesis in this small radicle of Cremohipparion whereby there may be two or more small Cremohipparion species of varying size. We refer a small suite of metapodials and phalanges to Cremohipparion aff. matthewi (Table 1). The size of this portion of the As Sahabi

INTRODUCTION As Sahabi is a latest Miocene fauna from North Africa. It is a true cross-roads fauna between western and southern Eurasia and East Africa (Bernor and Rook, this volume). The As Sahabi equids have provided tantalising evidence of the biogeographic affinities of the fauna, but their interpretation has been elusive because of the lack of complete skull material. Originally, Bernor et al. (1987) recognised two sizes of hipparionine horses at As Sahabi and referred these to a larger species, “Hipparion” cf. africanum, and a smaller and more gracile species, “Hipparion” cf. sitifense. Neither taxon can currently be supported (Bernor and Scott, 2003). There may have been a greater diversity of As Sahabi hipparions than previously recognised, and further work will be needed to determine to which superspecific groups they might best be referred. Solution of this issue would be greatly facilitated by new fossil material, and in particular skull material, and a rigorous analysis compared to later Miocene Eurasian and African lineages. Some new postcranial material collected by Boaz et al. in 2007 is included herein. This contribution is meant to aim us in the direction of better resolution of the systematics, biogeography and palaeoecology of the As Sahabi hipparions. How Many Equid Species May There Have Been at As Sahabi? Twenty years of systematic research on North American and Old World hipparionine horses suggested to Bernor

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Table 1. Plausible Attributions of Key As Sahabi Skeletal Elements to Hipparioninae Hipparion Taxon "Sivalhippus" sp.

cf. Hipparion s.s.

Cremohipparion aff. matthewi

?Cremohipparion nikosi

Specimen No. 2P111A 6P34A 77P16A 35P17A unlabelled 17P33A 314P28A 20P28A 1P11B 227P34A 1P42A 14P34A 43P34A 32P25B 25P26A 67P16A 468P28A 11P85A 6P108A 10P30A 470P28A 79P16B 6P109A 55P28A 48P25A 5P103A 5P109A 90P28A 54P16A 121P16A 5P96B 1P25B 31P25A 59P16A 3P201A 27P25B 33P16A 168P23A 242P28A 30P24 70P16A 35P25A

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Element 1PHIII distal MTIII distal MTIII distal MTIII distal MTIII distal MCIII Astragalus Astragalus Astragalus medial half Astragalus Astragalus Calcaneus Calcaneus 1PHIII distal MCIII MTIII distal 2/3rds MTIII distal MTIII proximal 3/4s MTIII proximal 1/2 MTIII Astragalus Astragalus lateral half Astragalus (>) Astragalus (>) Astragalus (<) Astragalus (<) Astragalus Calcaneus Calcaneus 2ndPHIII 3rdPHIII (post) MTIII distal MTIII distal MTIII distal MTIII MCIII distal MCIII ? proximal MTIII 2ndPHIII 3rdPHIII (post?) 3rdPHIII (ant?) p4

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to the Maragheh sample, but also is not so different from the holotype 1PHIII of Eurygnathohippus feibeli from the Lothagam Upper Nawata. We provisionally favor a referral of this specimen to cf. Hipparion s.s. because there is no evidence of any ectostylids on any permanent hipparion cheek teeth from As Sahabi. Bernor and Scott (2003) recognised a heavy-limbed form from As Sahabi which they believed to be a member of the Sivalhippus Complex. Bernor et al. (2005) and Bernor and Haile-Selassie (in press) have shown that a heavy-limbed lineage of hipparions was shared between the Siwaliks (circa 8-7 ma) and Kenya (circa 9-6 ma) and potentially as young as 4 ma in Ethiopia. The Siwalik hipparion has been referred to “Sivalhippus” perimense and the East African form to Eurygnathohippus turkanense. Skulls and postcrania, including 1PHIII’s are very similar, the difference principally being the presence of ectostylids on permanent lower cheek teeth of Eurygnathohippus turkanense. There are no teeth of the Eurygnathohippus morphology known at As Sahabi, which has led Bernor and Scott (2003) to refer the robust material to “Sivalhippus” sp. The large and robust 1PHIII (2P111A), which Bernor and Scott (2003) referred to “Sivalhippus” sp., is listed as such in Table 1. We also refer four distal MT III’s, a single distal MC III, five astragali, and two calcanei to this same taxon. Our current understanding of the As Sahabi hipparion fauna suggests that As Sahabi best correlates with early MN13, circa 6.5 ma. Biogeographically, As Sahabi exhibits temporally proximate relationships with the eastern Mediterranean Greek and Iranian faunas (plausible presence of two species of Cremohipparion and Hipparion

sample is not as small as the smallest Samos specimens often referred to C. matthewi, but it does conform to specimens the size of Cremohipparion aff. matthewi from Samos (Bernor, in progress) Limited dental evidence from As Sahabi (Figure 1) suggests that yet a second species of Cremohipparion, possibly referable to C. nikosi (= periafricanum), may also be present at As Sahabi, as exemplified by a very small, heavily worn mandibular p4, 35P25A (Table 1). This second Cremohipparion species is tiny, with very small and elongate metapodials. If As Sahabi is found to have this species, its occurrence there would suggest a Late Turolian (= MN13) correlation, circa 6.75.3 ma, with localities in Arabia, Greece, Italy, and Spain. Our recent comparison of a complete As Sahabi MT III, 67P16A to a homogenous sample of metapodials from MMTT13, Upper Maragheh, Iran (7.6 ma; Bernor, 1986; Bernor et al., 1996) reveals a close morphological similarity. The Maragheh specimens come from the MMTT13 quarry sample dominated by Hipparion campbelli, which is represented by the type skull, paratype cranial, and postcranial material. These MMTT 13 metapodials are similar in their size and proportions to the Mt. Luberon sample of Hipparion prostylum, the genotype locality for Hipparion s.s. (Woodburne and Bernor, 1980; Bernor and Wolf, under study). We therefore refer 67P16A to cf. Hipparion s.s. Table 1 lists several fragmentary metapodials, astragali, calcanea, and complete phalanges that we likewise refer to cf. Hipparion s.s. based on their size and comparisons to the Maragheh sample of Hipparion campbelli (Table 1). The As Sahabi 1PHIII, 32P25B, is broadly similar

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Figure 1. The As Sahabi equid dental assemblage (occlusal aspects). A: right maxillary P4 (4P16B), B: right maxillary P4 (35P99A), C: left maxillary P4 (1P85A), D: left maxillary P4 (19P33B), E: left maxillary P4 (130P16A), F: right maxillary P4 (251P22A), G: right maxillary M3 (63P109A), H: right maxillary M3 (212P34A), J: left maxillary M3 (16P108A), K: left maxillary molar (430P28A), L: right mandibular p4 (183P16A), M: right mandibular m1 (195P16A), N: left mandibular p4 (35P25A).

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0.5

87.5

5 5 0 5

20 10 5 10

75 85 95 85

5 10 5 5

45 80 30 20

50 10 65 75

bb cs eb eg dl Sahabi (DS2) Sahabi (DS1) Sahabi (DS3) Euhoo (LB) ct Sahabi (DS4) ab hn rr he cogoo ke coqui Me Ca Cc cosp (CH) To Ts Gg Gt Om GC OH hipri (HO) DS OJ OV DB AA RS

Figure 2. Hierarchical cluster diagram based on the mesowear parameters % high occlusal relief, % sharp cusps and % blunt cusps. Clusters base on a set of 27 “typical” extant species from Fortelius & Solounias (2000). Browsers: AA = Alces alces, DS = Dicerorhinus sumatrensis, GC = Giraffa camelopardalis, OH = Odocoileus hemionus, OJ = Okapia johnstoni, OV = Odocoileus virginianus, RS = Rhinoceros sondaicus, DB = Diceros bicornis. Grazers: ab = Alcelaphus buselaphus, bb = Bison bison, cs = Ceratotherium simum, ct = Connochaetes taurinus, dl = Damaliscus lunatus, eb = Equus burchelli, eg = Equus grevyi, he = Hippotragus equinus, hn = Hippotragus niger, ke = Kobus ellipsiprymnus, rr = Redunca redunca. Mixed feeders: Ca = Capricornis sumatraensis, Cc = Cervus canadensis, Gg = Gazella granti, Gt = Gazella thomsoni, Me = Aepyceros melampus, Om = Ovibos moschatus, To = Taurotragus oryx, Ts = Tragelaphus scriptus. Datasets of fossil species: As Sahabi sample: DS1 = upper P4-M3, sharpest cusp only; DS2 = upper P4-M3, both cusps; DS3 = upper and lower P4-M3, sharpest cusp only, DS4 = upper and lower P4-M3, both cusps. Cogoo = Cormohipparion goorisi, Coqui = Cormohipparion quinni (both after Fortelius & Solounias 2000), Cosp (CH) = Cormohipparion sp. from Chorora (Bernor et al. 2004), Euhoo (LB) = Eurygnathohippus hooijeri from the PPM-member of Langebaanweg, South Africa (after Franz-Odendaal, et al., 2003; Bernor and Kaiser, 2006), Hipri = Hippotherium primigenium 100 (after Kaiser, 2003).

Distance

s.s.) and with the South Asian-East African biogeographic corridor that shared members of the “Sivalhippus” Complex. Collection of more equid cranial and postcranial material from As Sahabi is crucial for refining our understanding of the age and timing of palaeogeographic connections with peri-Mediterranean, South Asian and East African bioprovinces.

What Were the Palaeodietary Preferences of the As Sahabi Equid Fauna? We are unable to clearly distinguish As Sahabi hipparion species based on the isolated cheek teeth currently available to us, with the exception of the very small form. Our future work will be to clarify the plausible systematic ties between the growing dental and postcranial material.

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Among other hipparion species analysed, the As Sahabi hipparion assemblage is found to have a dietary preference closest to Eurygnathohippus hooijeri from Langebaanweg, South Africa (Franz-Odendaal et al. 2003; Bernor and Kaiser, 2006) a member of the “Sivalhippus” Complex. None of the four members of the Cormohipparion clade, the North American C. goorisi and C. quinni (Fortelius and Solounias, 2000) the northern African “Cormohipparion” sp. from Chorora (Bernor et al., 2004) and the Central European Hippotherium primigenium (Kaiser, 2003) analysed so far had a diet dominated by graze to the same extent as indicated by the As Sahabi sample. In the future, it will be important to secure lineage-to-species level ties between the As Sahabi hipparion dental and postcranial material. When this is done we will be able to develop a more complete picture of As Sahabi evolutionary relationships and dietary adaptations.

Therefore, we had to treat the As Sahabi hipparion cheek tooth sample in bulk. We applied the mesowear method of dietary evaluation by Fortelius and Solounias (2000) and further modified by Kaiser and Solounias (2003) and Kaiser and Fortelius (2003) to include more tooth positions and lower, as well as upper, cheek teeth. This extended tooth model has been recently applied to fossil and extant equids by Kaiser et al. (2003), Kaiser and FranzOdendaal (2004), Bernor and Kaiser (2006), Kaiser and Bernor (2006), and Kaiser and Schulz (2006). We recorded mesowear signatures of 30 hipparion teeth from As Sahabi and performed analysis for four datasets representing the following fractions of the sample: DS1 = upper P4-M3, sharpest cusp only; DS2 = upper P4-M3, both cusps; DS3 = upper and lower P4-M3, sharpest cusp only, DS4 = upper and lower P4-M3, both cusps. Cluster statistics on mesowear variables was performed using Systat 11.0 Software licensed to TMK. As comparative datasets for dietary classification, we use a set of 27 “typical” extant herbivores (Fortelius and Solounias 2000) representing the three general feeding traits as grazers, mixed feeders and browsers (Figure 2). For extant comparison species we indicate monocot (%M) / dicot (%D) / fruit (%F) ratios given by Gagnon and Chew (2000). We find the As Sahabi hipparion datasets to consistently classify in the grazer spectrum of the mesowear continuum. Extant species comparisons include the wildebeest (Connochaetes taurinus) and the hartebeest (Alcelaphus buselaphus). Both African antelopes are grazers with monocot/dicot ratios in their diet ranging from 87.5%/12% (wildebeest) to 75%/20% (hartebeest), and the latter being more flexible in its feeding strategy then the former.

CONCLUSIONS Given its geographic position between Eurasia and sub-Saharan Africa it is not at all surprising that As Sahabi harboured four hipparion species. A strong influence from the eastern Mediterranean is likely, since so many other Turolian mammal taxa occur at As Sahabi (Bernor and Rook, this volume). There is no clear evidence of an East or South African hipparion clade being represented at As Sahabi, but this is a distinct possibility. The As Sahabi hipparions exhibit a strong grazing signature given its latest Miocene age and the remarkable shift to more seasonal open, open-country habitats at that time (Bernor et al., 1996; Fortelius et al., 1996). 165

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REFERENCES

Faunas (eds R.L. Bernor, V. Fahlbusch and H.-W. Mittmann). Columbia University Press, New York, 307-338.

BERNOR, R.L. (1986). Mammalian biostratigraphy, geochronology and zoogeographic relationships of the Late Miocene Maragheh Fauna, Iran. Journal of Vertebrate Paleontology 6 (1), 76-91.

BERNOR, R.L. and SCOTT, R.S. (2003). New Interpretations of the Systematics, Biogeography and Paleoecology of the Sahabi Hipparions (latest Miocene), Libya. Geodiversitas 25 (2), 297-319.

BERNOR, R.L., HEISSIG, K. and TOBIEN, H. (1987). Early Pliocene Perissodactyla from Sahabi, Libya. In: Neogene Geology and Paleontology of Sahabi (eds N.T. Boaz, J. de Heinzelin, W. Gaziry, A. El-Arnauti, and D. Boaz) New York, Liss, 233-254.

BERNOR, R.L., SCOTT, R.S. and HAILESELASSIE, Y. (2005). A contribution to the evolutionary history of Ethiopian hipparionine horses: Morphometric evidence from the postcranial skeleton. Geodiversitas 27 (1), 133-158.

BERNOR, R.L. and HAILE SELASSIE, Y. In press. Equidae. Fossil Vertebrates of the Late Miocene of Ethiopia. University of California Press.

FORTELIUS, M. and SOLOUNIAS, N. (2000). Functional characterization of ungulate molars using the Abrasion-Attrition wear gradient: A new method for reconstructing paleodiets. American Museum Novitates 3302, 1-36.

BERNOR, R.L. and KAISER, T.M. (2006). Systematics and paleoecology of the earliest Pliocene equid, Eurygnathohippus hooijeri n. sp. from Langebaanweg, South Africa. Mitteilungen aus dem Hamburischen Zoologischen Museum und Institut 103, 147-183. BERNOR, R. L., KAISER, T.M. and NELSON, S.V. (2004). The oldest Ethiopian hipparion (Equinae, Perissodactyla) from Chorora: Systematics, paleodiet and paleoclimate. Courier Forschungsinstitut Senckenberg 246, 213-226.

FORTELIUS, M., WERDELIN, L., ANDREWS, P., BERNOR, R.L. GENTRY, A., MITTMANN, H.-W. and V IRANTA S. (1996). Provinciality, diversity, turnover and paleoecology in land mammal faunas of the later Miocene of Western Eurasia. In: The Evolution of Western Eurasian Neogene Mammal Faunas (eds R.L. Bernor, V. Fahlbusch and H.-W. Mittmann). Columbia University Press, New York, 414-448.

B E R N O R , R . L . , K O U F O S , G . D. , WOODBUNE, M.O. and FORTELIUS, M. (1996). The evolutionary history and biochronology of European and Southwest Asian Late Miocene and Pliocene Hipparionine horses. In: The Evolution of Western Eurasian Neogene Mammal

FRANZ-ODENDAAL, T.A., KAISER, T.M. and BERNOR, R. L. (2003). A dietary evaluation of a fossil equid from South Africa – Implications for dietary adaptations during the late Miocene/early Pliocene. South African Journal of Science 99, 453–459.

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KAISER, T.M. and SCHULZ, E. (2006). Tooth wear gradients in zebras as an environmental proxy - A pilot study. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 103, 187-210.

GAGNON, M. and CHEW, A. E. (2000). Dietary preferences in extant African Bovidae. Journal of Mammalogy 81, 490511. KAISER, T.M. (2003). The dietary regimes of two contemporaneous populations of Hippotherium primigenium (Perissodactyla, Equidae) from the Vallesian (upper Miocene) of Southern Germany. Palaeogeography, Palaeoclimatology, Palaeoecology 198, 381-402.

KAISER, T.M., SOLOUNIAS, N., FORTELIUS, M., BERNOR, R.L. and SCHRENK, F. (2000). Tooth mesowear analysis on Hippotherium primigenium from the Vallesian Dinotheriensande (Germany) - A blind test study. Carolinea - Beiträge zur naturkundlichen Forschung in Südwestdeutschland 58, 103-114.

KAISER, T.M. and BERNOR, R.L. (2006). The Baltavar Hippotherium: A mixed feeding Upper Miocene hipparion (Equidae, Perissodactyla) from Hungary (East-Central Europe). In: "Festschrift für Gudrun Höck" (eds D. Nagel and L. W. Van den Hoek Ostende). Beiträge zur Paläontologie 2006 (30), 241-267.

KAISER, T.M. and SOLOUNIAS, N. (2003). Extending the tooth mesowear method to extinct and extant equids. Geodiversitas 25 (2), 321-345. WOODBURNE, M.O. and BERNOR, R.L. (1980). On superspecific groups of some Old World hipparionine horses. Journal of Paleontology 54 (6), 1319-1348.

KAISER, T.M., BERNOR, R.L., SCOTT, R.S., FRANZEN, J.L. and SOLOUNIAS, N. (2003). New interpretations of the systematics and palaeoecology of the Dorn-Dürkheim 1 hipparions (Late Miocene, Turolian Age (MN 11), Rheinhessen, Germany. Senckenbergiana Lethaea 83, 103-133. KAISER, T.M. and FORTELIUS, M. (2003). Differential mesowear in occluding upper and lower molars - Opening mesowear analysis for lower molars and premolars in hypsodont equids. Journal of Morphology 257 (1), 67-83. KAISER, T.M. and FRANZ-ODENDAAL, T. (2004). A mixed feeding Equus species from the Middle Pleistocene of South Africa. Quaternary Science Reviews 62, 316-323.

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Systematics and Biogeographic Relationships of As Sahabi Suidae GIANNI GALLAI, RAYMOND L. BERNOR, and LORENZO ROOK

ABSTRACT

The Sahabi Formation has yielded fossil remains of three suid taxa, recognised here as Nyanzachoerus syrticus, Nyanzachoerus cf. devauxi, and Nyanzachoerus kanamensis. The As Sahabi suids show biogeographic relationships to Arabia, East and South Africa, and likely had their origins from South Asian Middle and Late Miocene tetraconodont suids belonging to the genus Conohyus.

Giani Gallai and Lorenzo Rook, Dipartimento di Scienze della Terra, UniversitĂ di Firenze, Via G. La Pira 4, 50121 Firenze, Italy Raymond L. Bernor, College of Medicine, Department of Anatomy, Laboratory of Evolutionary Biology, Howard University, 520 W St., N.W. Washington D.C. 20059, U.S.A; and National Science Foundation, GEO:EAR Sedimentary Biology and Paleobiology Program, Arlington, VA 22230

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latest Miocene of Eurasia and Africa includes three genera of Tetraconodontinae: Sivachoerus and Tetraconodon in South Asia and Nyanzachoerus in Africa. The genus Notochoerus, on the other hand, is not known in Africa until the Early Pliocene. Van der Made (1999a) transferred many Mio-Pliocene African species from Nyanzachoerus to Sivachoerus and recognized two separate lineages: the Nyanzachoerus-Notochoerus clade and one that leads to the differentiation of several separate species of Sivachoerus (e.g Van der Made, 1999a, Fig. 19). Harris and Leakey (2003) have demonstrated that there are some major discrepancies in Van der Made’s taxonomic recombinations, and have continued to recognize the African tetraconodont genera Nyanzachoerus and Notochoerus. This is particularly important for the As Sahabi suid fauna which includes two species, Nyanzachoerus devauxi and Nyanzachoerus syrticus. During the latest Miocene, Eurasian Suinae include the genera Korynochoerus (=?Propotamochoerus) and Microstonyx (=?Hippopotamodon) (Van der Made, 1989-90). The genus Propotamochoerus was erected by Pilgrim (1926) on the basis of material from the Siwaliks. Since the 1980’s, several researchers have recognised Korynochoerus as being the junior synonym of Propotamochoerus (Ginsburg, 1980; Pickford, 1988; Made and MoyaSolà, 1989; Fortelius et al., 1996). In the past, Microstonyx has been considered as synonym of the genus Hippopotamodon (Van der Made, 1999b). However, Bernor and Fessaha (2000) and Liu et al. (2004) have demonstrated that their premolar morphology and size differ significantly,

INTRODUCTION Old World suid faunas underwent a series of turnovers in the Middle and Late Miocene. During this interval, the archaic Early and Middle Miocene subfamilies the Hyotherinae, Kubanochoerinae, and Listriodontinae became extinct and were replaced by the Tetraconodontinae and Suinae. The Tetraconodontinae became severely restricted in Eurasia by the early Late Miocene (Vallesian age), but underwent an evolutionary radiation in the Late Miocene and Pliocene of Africa. The Suinae were dominant in Eurasia in the Late Miocene - Pleistocene, and evolved endemic lineages in the African latest Miocene – Pleistocene. Asia would appear to have been a major source for immigration of suines and tetraconodonts into Europe and Africa, but the timing of these events remains elusive today (Pickford, 1993). The dynamics of central and eastern Paraethys regressions, uplift of the Alpine-Himalayan mountain chain, and climate change all likely contributed to the regulation of suid migrations (Rögl, 1999a, 1999b; Bernor et al., 2003). The Tetraconodontinae are characterized as suids that progressively enlarge their posterior premolar teeth (Fortelius, et al., 1996). European Middle Miocene forms generally exhibit the least derived condition (Bernor, et al., 2003), and Asian Late Miocene forms exhibit the most derived condition (Pickford, 1988; Van der Made, 1999a). While some African forms have enlarged posterior premolars, they do not evolve the massiveness of the South and Southeast Asian forms Tetraconodon magnus and Tetraconodon minor. The

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devauxi, and its recognition at As Sahabi. We maintain recognition of three suid species at As Sahabi: Nyanzachoerus kanamensis, Nyanzachoerus cf. devauxi, and Nyanzachoerus syrticus. Nyanzachoerus kanamensis most likely is derived from some restricted sedimentary package of younger age (see Boaz et al., this volume). It has a short and simple M3 with three pairs of cusps. Nyanzachoerus syrticus is smaller with greatly expanded posterior premolars and relatively small and simple third molars (Van der Made, 1999a; Harris and Leakey, 2003). Nyanzachoerus devauxi differs from Ny. syrticus in its smaller size and longer premaxilla, and from Ny. waylandi by its larger premolars but smaller molars.

warranting their generic distinction. We will review here, in greater detail, As Sahabi’s suids and their biogeographic relationships to other later Turolian (MN12 and 13) Suidae, with particular emphases on Europe, South Asia and East Africa, updating Fortelius et al. (1996). THE SAHABI SUID FAUNA Petrocchi (1943, 1951) initially reported a suid partial skull and a mandible from As Sahabi. Leonardi (1952, 1954) first described these specimens and assigned them to Sivachoerus cf. giganteus (skull) and Sivachoerus syrticus (mandible). Cooke and Ewer (1972) further revised the nomenclature for the skull and transferred it to Nyanzachoerus pattersoni. Kotsakis and Ingino (1980) also restudied the specimen and proposed the new name Nyanzachoerus cookei. Cooke (1987) rejected this assignment and referred the skull to Nyanzachoerus kanamensis. Cooke and Ewer (1972) referred the mandible to N. tulotos but Cooke (1987) later argued that this specimen is best referred to Nyanzachoerus syrticus. Based on the International Sahabi Research Project material Cooke (1987) who studied the skull and dental material, and McCrossin (1987) who studied the postcranial materials, collectively recognised two species of nyanzachoere: the smaller form Nyanzachoerus cf. devauxi and the larger form Ny. syrticus. Van der Made (1999a) subsequently synonomized Ny. cf. devauxi with Conohyus giganteus. Harris and Leakey (2003) have argued for the maintenance of the nomen Nyanzachoerus

BIOGEOGRAPHIC RELATIONSHIPS OF THE AS SAHABI SUID FAUNA All European Turolian age (MN 1113, 8.7-5.3 ma) suids are referable to the Suinae. Propotamochoerus provincialis occurs in Europe throughout the interval and is present in Hungary (Fortelius, 1996) and in Italy (Rook and Ghetti, 2002, Gallai, 2005, Gallai and Rook, 2006). Eumaiochoerus is known only from the endemic faunas of Tuscany (Hürzeler, 1982; Hürzeler and Engesser, 1976; Bernor et al., 2001., Abbazzi et al., in press). This taxon becomes ubiquitous, albeit often represented by small sample sizes during the Turolian of Hungary (MN11/12 of Baltavar and MN12/13 of Polgardi; Bernor and Fessaha, 2000), Greece (Koufos, 2006), Turkey (Fortelius, 1996), Georgia (Bazaleti MN13, Gallai, pers. observ.), Kyrgyztan

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and Rook (this volume). As noted by Hill (1999), the African deposits attributable to the later part of the Late Miocene are relatively rare. Notwithstanding, they very often yield fossil suids mostly belonging to the Tetraconodontinae. Lothagam (Kenya) is an important site southwest of Lake Turkana. Harris and Leakey (2003) have reported a diverse suid fauna from the Nawata Formation including Kubanochoerus sp. (Kubanochoerinae); Nyanzachoerus syrticus tulotus, Nyanzachoerus cf. Ny. syrticus, Nyanzachoerus cf. Ny. australis, Nyanzachoerus devauxi (Nyanzachoerinae); and Propotamochoerus (Suinae). As Sahabi and the Lothagam Nawata Formation share Ny. devauxi and Ny. syrticus in common, but Harris and Leakey (2003) observe that the Lothagam forms are smaller and less progressive (sensu Harris and White, 1979) than the As Sahabi ones. Cooke (1987) also observed similarities between the As Sahabi and Lothagam suid faunas, and proposed a correlation between As Sahabi and Lothagam 1B -1C Member corresponding to the Upper Nawata and Apak Members of Lothagam (Feibel, 1999). Harris and Leakey (2003) concurred with Cooke in correlating As Sahabi with the latest Miocene based on its larger size that the Lothagam Nawata forms. A succession that ranges from about 16 ma to the Pleistocene has been discovered in the Tugen Hills, Kenya. The faunas of most interest for comparison with As Sahabi are Mpesida (ca. 7-6 ma) and Lukeino (ca.6-5 ma). Nyanzachoerus indet. was reported from Mpesida but, because of its fragmentary nature, species-level comparisons are not possible. The Lukeino

(Fortelius, 1996) and Iran (MN 11-12, Bernor, 1986). There is no evident biogeographic relationship between the eastern Mediterranean and Southwest Asian latest Vallesian and Early Turolian suid faunas and the As Sahabi suid fauna. Sivachoerus is common in the upper part of Dhok Pathan Formation of the Siwalik Hills. The third and fourth premolars are even larger relative to the anterior premolars and molars than in Nyanzachoerus. The mandible of Sivachoerus is much more massive than in Nyanzachoerus (Bishop and Hill, 1999). Suinae are also represented in the Indian Subcontinent with the occurrence of the genera Propotamochoerus and Hippopotamodon. There is no basis to believe that there is a biogeographic relationship between Siwalik Dhok Pathan and As Sahabi suid faunas. In the Arabian Peninsula, the most complete documentation relating to the Middle and Late Turolian comes from the study of the fauna discovered in the Baynuna Formation (Abu Dhabi). The age of this formation appears to be about 8 ma to 6 ma (Whybrow and Hill, 1999). Nyanzachoerus cf. syrticus was discovered in Abu Dhabi (MN11-13) and in Shuwahiat. Nyanzachoerus indet. has been reported from the United Arab Emirates, specifically from the deposits of Hamra (Whybrow and Hill, 1999), and hence exhibits affinities with the As Sahabi suid fauna. Bishop and Hill (1999) argued that the direction of biogeographic extension was from Africa to the Arabian Peninsula. The relationship between the As Sahabi and Abu Dhabi latest Miocene large mammal faunas has been demonstrated by Bernor

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the Quartzose Sand Member contains Nyanzachoerus australis. The Langebaanweg fauna is apparently latest Miocene-earliest Pliocene correlative.

material has been identified by Harris and Leakey (2003) as an advanced form of Nyanzachoerus syrticus and Ny. pattersoni (also found at Lothagam). An additional site of interest because of the presence of suids during the latter part of Late Miocene is the Lake Albert Basin (Uganda, DR Congo), in which the Nkondo Member of the Nkondo Formation is dated to 7-6 ma. Species reported here include Listriodon jeannelli, Potamochoerus sp., Nyanzachoerus waylandi (Senut et. al., 1994), Nyanzachoerus jaegeri (Senut et. al., 1994), Nyanzachoerus australis (van der Made 1999a), and Nyanzachoerus tulotus (Senut et. al., 1994). The molars of Ny. waylandi are larger than those of As Sahabi Ny. devauxi (Cooke, 1987). According to Harris and Leakey (2003), Ny. waylandi is a more progressive taxon than Ny. devauxi. In any case, the two species are closely related, and van der Made (1999a) regarded Ny. waylandi as a subspecies of Ny. kanamensis. Nyanzachoerus waylandi (Senut, et al., 1994) was also discovered in Nyaburogo, Uganda. Nyanzachoerus kanamensis, the same species found at As Sahabi, has been discovered within the Manonga Formation (latest Miocene - medial Pliocene age) in Tanzania. However, Bishop (1997) has observed that the teeth of this taxon are more robust than those of Ny. kanamensis and resemble Ny. australis. Nyanzachoerus kanamensis is also known from the locality of Kanam, Kenya (Harris and White, 1979). The only South African site containing Late Miocene suids is Langebaanweg (Hendey, 1981). The fossil assemblage derived from the Pelletal Phosphorite Member contains Cainochoerus while the assemblage from

PROVINCIALITY OF WESTERN EURASIAN AND AFRICAN SUID FAUNAS Fortelius et al. (1996) indicate that MN12/13 is a transitional period in western Eurasian mammal faunas, and one in which there are apparent provincial suid extinctions. We cite evidence here that provinciality of western Eurasian and African suid faunas occurred from the beginning of the Turolian, ca. 8.7 ma. Central Europe, Southeast Europe, and Western Asia were dominated by suines of the Propotamochoerus and Microstonyx clades. They in turn were distinct from the Siwalik Dhok Pathan suid faunas which were dominated by the suines Propotamocheorus and Hippopotamodon. A highly derived tetraconodont, Tetraconodon minor may also have occurred in Dhok Pathan. As Sahabiâ&#x20AC;&#x2122;s tetraconodont taxa Ny. devauxi and Ny. kanamensis (= pattersoni) have distinct biogeographic relationships to East African Late Miocene â&#x20AC;&#x201C; Early Pliocene faunas. The occurrence of Ny. syrticus at As Sahabi confirms a connection both to Arabia and East Africa in the latest Miocene. Development of strong provinciality in Late Miocene Western Eurasian-African suid faunas may prove to be due to increased climatic zonation across this geographic expanse, with tropical climates contracting toward the equator. East Asia participated in this provinciality, having connections

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relationship between the South Asian Sivachoerus and African Nyanzachoerus lineages has been proposed by many authors (e.g. Cooke, 1987, Pickford, 1988). However, as noted by Bishop and Hill (1999) and more recently by Harris and Leakey (2003), the Sivachoerus clade is thus far known only from the Indian subcontinent. We confirm here that the As Sahabi suid fauna has a close biogeographic relationship with South Asia, Arabia, and in particular, East Africa. The age of As Sahabi has long been debated. We concur with Howell (1987), Cooke (1987), Harris and Leakey (2003), Bernor and Rook (this volume) and Boaz et al. (this volume) that Sahabi is best correlated with the Upper Nawata of Lothagam and MN13 of the European Neogene time scale (Steininger et al., 1996).

with Western Eurasia in its occurrence of Microstonyx erymanthius (=major), but being distinctly endemic in its occurrence of the small suine, Chleuastochoerus (Liu, et al., 2004). Liu (2004) has argued that northern China was biogeographically distinct from southern China and the Siwaliks in the latest Miocene. The Late Miocene northern Chinese faunas were probably not a contributing source for Late Miocene Arabian and African mammal migrations. CONCLUSION The distribution of Late Miocene African tetraconodonts probably reflects a late Middle Miocene or early Late Miocene faunal extension from South Asia. The African tetraconodonts share little in common with Middle Miocene European tetraconodonts (Bernor, et al., 2003). We agree with Bishop and Hill (1999) that the occurrence of Ny. syrticus in Arabia is likely the result of a Late Miocene extension from North Africa. From a likely South Asian geographic source, the genus Conohyus probably entered Africa around the Middle-Late Miocene transition and represented a plausible founding population at the base of the African tetraconodont radiation. While Nyanzachoerus devauxi had a biogeographic range limited to North Africa and the northern East African rift, Nyanzachoerus syrticus exhibited a broader geographic distribution that extended from Arabia to East Africa. Nyanzchoerus kanamensis was also relatively widely distributed in Africa from Libya to Tanzania. As Sahabi has yet to yield any record of a suine, which argues for its complete disjunction from northern Mediterranean and southwest Asian suid faunas. The possible phylogenetic

ACKNOWLEDGEMENTS We thank N. Boaz and A. ElArnauti for their energy in putting together the ELNRP (East Libya Neogene Research Project) and for the invitation to contribute to this volume. RLB and LR would like to acknowledge the current structural framework for Late Miocene and Early Pliocene hominid evolution provided by the Revealing Hominid Origins Initative funded by the National Science Foundation (NSF grant BCS-0321893) to F. Clark Howell and Timothy D. White, U.C. Berkeley). This paper is developed within the research programs of R.L. Bernor, Evolution of Old World Neogene Mammal Faunas at Howard Universityâ&#x20AC;&#x2122;s Laboratory of Evolutionary Biology, and L. Rook, Late Neogene Vertebrate Evolution at the University of Florence.

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Società Paleontologica Italiana 40, 139148.

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HOWELL , F.C. (1987). Preliminary observations on Carnivora from the Sahabi Formation. In: Neogene Paleontology and Geology of Sahabi (eds N.T. Boaz, A. ElArnauti, A.W Gaziry, J. de Heinzelin and D.D. Boaz ). Liss, New York, 153-181.

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HÜRZELER, J. and ENGESSER, B. (1976). Les faunes des mammiferes Neogenes du Bassin de Baccinello, C.R Acad. Sci. Paris, 283(2), 333-336.

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Special Issue, No. 5

Rediscovered Hippopotamid Remains from As Sahabi

PARIS PAVLAKIS

ABSTRACT The anterior mandibular morphology of Hexaprotodon sahabiensis is evinced for the first time by previously undescribed mandibular fragments collected at As Sahabi by Petrocchi in the late 1930â&#x20AC;&#x2122;s, and housed since then in the National Museum of Libya, Tripoli. The sagittal cross-section of the mandibular symphysis shows a unique configuration for Neogene African Hippopotamidae species. The new Hex. sahabiensis morphological data permit a preliminary comparison with both Saotherium and Archaeopotamus (Boisserie, 2005). Hex. sahabiensis compares in overall mandibular shape with Archaeopotamus.

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These specimens were assigned by Petrocchi to Hexaprotodon based on the alveoli of the six incisors of the skull #15. The same referral was made by Coryndon (1978). The actual specimens, however, were considered lost. The next hippopotamid sample from As Sahabi was discovered by I.S.R.P., during the field seasons 1977 to 1981. The recovered fossil hippopotamid sample consists of about 160 specimens. Of those, about 40% were craniodental material and they were described by Gaziry (1987). Gaziry (1987) erected a new hippopotamid species: Hexaprotodon sahabiensis. Hexaprotodonty was based on Petrocchi΄s reported observation, most probably that of the mandible (#14) and skull (#15), as well as on the three incisor alveoli on the right premaxilla 172P11A discovered by I.S.R.P. (Gaziry, 1987: Fig. 3, p. 306). Here, I describe three previously undescribed hippopotamid specimens from As Sahabi (as labeled) located during a visit of Noel Boaz to the National Museum in Tripoli in 2004 and studied by me in October 2007. The most complete of the three specimens is a fairly complete anterior part of a mandible. Most probably it is the specimen #14 of Petrocchi΄s 1952 report of his 1939 palaeontological field season.

INTRODUCTION Before the onset of palaeontological research in As Sahabi by the International Sahabi Research Project (I.S.R.P.) in 1974, and by the East Libya Neogene Research Project in 2004, fossil hippopotamid material collected from As Sahabi had been last reported in 1952 (Petrocchi, 1952:24, 26-27). Petrocchi reported four hippopotamid specimens (#13-16). They had been discovered during his 4th field campaign (Jan-March,1939), in the area NNW of the Qasr As Sahabi, at the “12th km pole of the road Sahabi-Ajdabya”. Their localities were noted on his map titled “Rilievo Topographico dela Zona Fossilifera di Sahabi” (Petrocchi, 1952: Tav I). He gives no description or figure, however, other than the following information: - a cranium in very bad state of preservation [#13], with only part of the maxilla being salvageable. It was found in Locality 55. - a mandible, [#14] collected near #13, embedded in the sand. It had six incisors, and preserved the horizontal and the vertical rami. The molars were very worn and fragmented (Locality 56). - 3 km north of the “campo di aviazione”, a complete skull was found immersed in the sand [#15]. The occipital, parietal and maxillary parts were in excellent condition, while the nasal was missing. The incisors were also missing, but the six alveoli revealed its hexaprotodonty. It was found in Locality 57. Finally, - in the Locality 58, a badly damaged mandible was reported [#16].

HIPPOPOTAMID MATERIAL As Sahabi #4 (provisional Libya National Museum ID) anterior mandibular fragment with LI/1, LI/2, RI/2, RI/3, R/C As Sahabi #1 Left mandibular fragment with LM/1, LM/2 As Sahabi #2 Right posterior mandibular body with M/3 germ.

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Figure 1. Hex. sahabiensis anterior mandible with R/C, R/I3, R/I2, LI/1, LI2, dorsal view. Scale unit 5 cm

lay at the same general level of the dorsal symphysial plane (inclined antero-dorsally). The incisors relative position is also roughly linear. The I/2s in both sides are attached to the 1st incisors (the RI/1 is documented by the tooth fragment revealed into the alveolus, Figure 2a). I/3Î&#x201E;s are about 6 cm high, while the I/2Î&#x201E;s about 3 cm. The incisors present close to horizontal occlusal wear facets (tilted lingually at an angle of about 45o to their long axis). The I/2s are considerably smaller than both I/1 and I/3s (Figure 2b). The I/1 is wider (horizontal diameter) than long (vertical diameter), while the opposite is true for I/3, which otherwise has similar size (Figure 2a). There is almost no inter-I/1 diastema. If we apply the same character states used by Boisserie (2005), in his recent

DESCRIPTIONS As Sahabi #4 is an anterior mandibular fragment (Figure 1) with complete symphysial region. The right horizontal ramus is preserved up to the level mesially to M/3 alveolus, while the left ramus is missing posteriorly to about the M/1. The right anterior portion of the mandible is complete, with R/C, RI/3 and RI/2 intact. RI/1 is broken and the alveolar portion of the tooth was revealed after we removed glue and plastering material that blocked the incisorÎ&#x201E;s alveolar opening (Figure 2a). The left anterior mandibular side is more damaged than the right. Only the LI/1 and LI/2, attached to it, are surviving. LI/3 and the L/C are broken (Figure 2b, 4b). The procumbent incisors

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Figure 2. (a) Anterior view, and (b) dorsal close up view (b) of Hex. sahabiensis anterior dentition. R/I1 is broken, showing only the alveolar part, R/I2, R/I3, R/C, LI/1, LI2. Scale unit 1 cm. horizontal rami at about 450, [Character state 18(1) in Boisserieâ&#x20AC;&#x2122;s (2005) analysis]. The anterior symphysis length is 127 mm and it is almost flat (Figure 1). The inferior configuration of the symphysis cross section presents an abrupt angle at the posterior part of the cross section, (approximately 72X42 mm2 anterior or frontal surface area, versus 55X64 mm2 posterior or ventral surface area (Figure 4a,

comprehensive cladistic analysis of the family Hippopotamidae, Sahabi #4 exhibits the character state 23(0): I/1-I/1 diastema shorter than the mesiodistal diameter of the I/1 (Boisserie 2005:26). The canine is broken, preserving approximately 10 cm of its height. The lower part of the concave vertical wear facet with the upper canine is preserved. The mesial surface of the canine is flat, while the distal is quite rounded. No enamel morphology can be observed. The anterior border of the canine alveolus is located slightly posteriorly to the level of incisor alveoli. The canine process is poorly developed and does not diverge much laterally to the P-M tooth row. Teeth length-width dimensions are reported in Table 1. Postcanine teeth do not survive. The anterior mandibular fragment preserves the complete symphysial area. The shape of the symphysis sagittal cross section is drawn in Figure 3. It is inclined upwards from the general level of both

Table 1. Dimensions of anterior teeth in mm, of Sahabi #4 Hex. sahabiensis from As Sahabi. L

182

Sahabi # 4 LI/1

22.28

27.54

Sahabi # 4 LI/2

20.14

16.40

Sahabi # 4 RI/2

21.68

16.12

Sahabi # 4 RI/3

25.02

22.92

Sahabi # 4 R/C

60.48

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Figure 3. Schematic Hex. sahabiensis symphysis sagittal cross-section. Scale unit 1 cm. 4b). The incisor alveolar process is continuous between the two canines, and forms an overhang relative to the frontal face of the symphysis of about 48 mm thickness. The measured mandibular dimensions follow Pavlakis (1990) and the dentition dimensions follow Gaziry (1987). The measurements on the mandibular fragment that can be taken are: Length of the mandibular symphysis = 127.00 mm Minimum thickness of canine apophysis = 58.48 mm Minimum thickness of mandibular body just mesial to right P/3 alveolus = 63.00 mm Minimum width of the canine alveoli = 112.08 mm Minimum width of the mandible taken at the buccal sides of both horizontal rami at the level of P/2s = 183.00 mm Height of the right horizontal ramus taken vertically at the level mesially to right P/2 alveolus = 82.50 mm Height of the right horizontal ramus taken vertically at the level mesially to right M/2 alveolus =105.58 mm

Figure 4. Hex. sahabiensis anterior mandible, (a) right lateral view, (b) ventral view. Scale unit 5 cm.

Sahabi #1 is a left mandibular fragment with LM/1 and LM/2 (Figure 5a). M/1 shows considerable wear, while M/2 has moderate wear. It compares with Hip. amphibious age group XIV of Laws (1968). The left horizontal mandibular ramus preserves in length only the area from the of 4th premolar to the 3rd molar. This mandibular piece of the horizontal ramus is complete only for approximately

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Table 2. Dimensions of molar teeth (mm) of As Sahabi # 1 Hex. sahabiensis

Want

Wpost

Sahabi #1 LM/1

36.42

25.78

26.38

Sahabi #1 LM/ 2

22.92

11.48

18.02

M/2, measures 111.32 mm. The molar measurements are shown in Table 2. M/1 is worn almost to the bottom of the transverse valley. It is more worn on the buccal side. The protoconid and the metaconid are united. The hypoconid and entoconid show less wear exhibiting the typical hippotamid â&#x201E;Ś enamel configuration (Figure 5b). The cingulum extends unevenly all around the occlusal surface, more mesially and distally. Interstitial wear is present. The M/2 occlusal surface presents the 4 cusps worn down to about half their height, as well as the transverse valley and the cingulum. Sahabi #2 is a right posterior mandibular body fragment with an M/3 germ just raising from its alveolus (Figure 5c). The mandibular fragment extends in length at the buccal side, mesially from the small mental foramen to distally about half the ascending ramus. M/2 is missing, and the M/3 germ is in situ. The gonial angle area is missing, preserving only its origins. The only mandibular body measurement that can be estimated is the height of the right horizontal ramus. Taken

Figure 5. Hex. sahabiensis mandiblar fragments #1 (a, buccal, b, occlusal view) and #2 (c, lingual view). Scale unit 5 cm. the length of M/1. The height of the horizontal ramus, taken vertically to the occlusal surface at the level mesially to

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expansion of the canine processes, the relative length of the symphysis, the shape of the symphysis cross-section, and the length of the premolar row relative to molar row. Hex. sahabiensis was not included in this cladistic analysis because of the inadequate sample known from As Sahabi until 2003. However premature it may be to accept this new phylogeny within the Hippopotamidae, nevertheless, it is so far the most recent and comprehensive attempt to establish new apomorphies in hippotamid phylogeny. The new mandibular Hex. sahabiensis data reported in this study provide the opportunity to make preliminary comparisons on the basis of this new phylogenetic hypothesis. For this reason, the new species nomenclature used in this phylogeny is followed. The new material studied here verifies that Hex. sahabiensis is a hexaprotodont hippopotamid. Of the six lower incisors, both 2nd incisors are much smaller that the subequal 1st and 3rd lower incisors. The 1st is the largest, and presents a flatter cross-section than the more cylindrical 3rd. The 2nd lower incisors are almost attached to the 1st. All six incisors are aligned, with the 2nd being located slightly posteriorly and dorsally to the larger 1st. The shape of the Hex. sahabiensis symphyseal sagittal cross-section, compared with the mandibular anatomy within the Hippopotamidae (Boisserie, 2005, Fig. 9, p. 13), presents a unique configuration among African Neogene hippopotamids. Specifically, unique morphological characteristics include: the quite thick anterior part of the symphyseal cross-section, and the acute angle the crest makes on the lower symphyseal surface,

vertically at the level mesial to the right M/2 alveolus, it measures 83.54 mm (comparing to 105.58 mm of Sahabi #1). No measurements can be taken on the molar germ. It exhibits the typical hippopotamid 3rd molar five-cuspid configuration. DISCUSSION As Sahabi #4 anterior mandibular fragment provides the opportunity to document for the first time the general shape of the Hexaprotodon sahabiensis mandible. Specifically it demonstrates: 1) Hex. sahabiensis adult anterior dentition, 2) the degree of expansion of the mandibular canine processes, and 3) the relative length and sagittal cross-sectional configuration of its mandibular symphysis. These morphological characters are crucial, since they enable the Hex. sahabiensis sample to be included in studies to update the taxonomy of the Family Hippopotamidae. Boisserie (2005), in a recent comprehensive cladistic analysis, attempts a revision within the Hippopotamidae of the last 8 ma of African and Asian species. In his proposed new phylogeny, Hexaprotodon is considered paraphyletic. He maintains this genus for the Asian mostly species and splits the rest of African Hexaprotodon species into two new genera, Saotherium (from Chad) and Archaeopotamus (mostly from Lothagam, including Hex. harvardi and Hex. aff. sahabiensis from Abu Dhabi). He reinstates Choeropsis for the extant pygmy hippo, and relates it to the Saotherium clade (Boisserie, 2005: Fig. 10, p. 14). He establishes new mandibular morphological criteria to support these clades. These include the

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between the frontal and ventral faces (character 19 in Boisserie`s cladistic analysis). The anterodorsal (upwards) orientation of the symphyseal plane and the linear position of the incisors characterise the new genus Saotherium (Boisserie, 2005). Hex. sahabiensis shares these characters with this new genus, and compares more closely to Saotherium mingoz (Boisserie et al., 2003, Fig. 3, p. 18). This hippopotamid is of Early Pliocene age (from ca. 5 ma old strata of Kolle), and appears smaller than Hex. sahabiensis from As Sahabi and Abu Dhabi (Boisserie et al., 2003). The hippotamid material from the older Toros-Menalla fossiliferous area in Chad is still under study. Since, however, the anthracothere dental anatomy suggests a continuous Late Miocene Chado-Libyan bioprovince (Lihoreau et al., 2006, also Pavlakis and Boaz, this volume), the hippopotamids from As Sahabi and TorosManella can be expected to be similar. It is not the purpose of this study, and we do not have yet the adequate hippopotamid sample from As Sahabi, to delineate true morphological relations between Hex. sahabiensis and S. mingoz. On the other hand, the general shape of the mandible, in particular the small expansion of the canine process and the long symphysis, compares with Archaeopotamus, and more precisely with Archaeopotamus aff. logathamensis (Boisserie, 2005, Fig 9, p. 13) and A. lothagamensis (Weston, 2000). We do not yet have, however, a mandibular specimen of Hex. sahabiensis to accurately estimate the P2-4 length relative to the molar row. This is necessary in order to clarify the relation of Hex. sahabiensis to Saotherium

or to Archaeopotamus.Based on the size of isolated premolars, Hex. sahabiensis seems to have a quite high P/M tooth row index and is, thus, closer to Archaeopotamus in that character than to Saotherium. This similarity is in addition to the similarity in overall shape of the anterior mandible (i.e., long symphysis and poorly developed canine processes). In fact there seems to be a size gradient from A. lothagamensis to A. harvardi, with Hex. sahabiensis being closer in size to A. lothagamensis. The same seems to be true with the lateral expansion of the anterior mandible. Hex. sahabiensis canines are close to the postcanine dental arcade line, like in A. lothagamensis, while the mandible of A. harvardi is the widest anteriorly, in addition to being the largest of the three species. This morphological size gradient poses the need of examining it under the light of the new Hex. sahabiensis sample, in order to reevaluate the relations between A. lothagamensis and Hex. sahabiensis. A crucial question is the validity of these two species names, and specifically whether the species name sahabiensis includes lothagamensis due to nomen priority. ACKNOWLEDGMENTS Noel T. Boaz, International Director of E.L.N.R.P., rediscovered the hippopotamid fossils in the Tripoli National Museum. Giuma Anag, Chairman of the Department of Archaeology, permitted me to study the material. Research was supported by NSF grant to B. Benefit, M. McCrossin, and N.T. Boaz, New Mexico State University, (subcontractor, P.

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Pavlakis, University of Athens), by NSF RHOI funds, and by E.L.K.E funds from the University of Athens. Shell Exploration and Production Libya GmbH is funding the museum restoration.

(2006). Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince. PNAS 103 (23), 8763-8767. PAVLAKIS, P.P. (1990). Plio-Pleistocene Hippopotamidae from the Upper Semliki. Virginia Mus. Nat. Hist. Memoir 1, 203223.

REFERENCES BOISSERIE, J.R. (2005). The phylogeny and taxonomy of Hippopotamidae (Mammalia: Artiodactyla): a review based on morphology and cladistic analysis. Zoological Journal of the Linnean Society 143, 1-26.

PETROCCHI, C. (1952). Notizie generali sul giacimento fossiliero di Sahabi. Storia de scavi—Risultati. Rend. Accad. Naz. Quaranta 3, 9-34. VIGNAUD, P., DURINGER, P., MACKAYE, H.T., LIKIUS, A., BLONDEL, C., BOISSERIE, J.-R., DE BONIS, L., EISENMANN, V., ETIENNE, M.-E., GERAADS, D., GUY, F., LEHMANN, T., LIHOREAU, F., LOPEZM ARTINEZ , N., M OURER -C HAUVIRΘ , OTERO, O., RAGE, J.-C., SCHUSTER M., VIRIOT, L., ZAZZO, A. and BRUNET., M. (2002). Geology and palaeontololgy of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature 418, 152-155

BOISSERIE J-R., AND VIGNAUD,

BRUNET, M., ANDOSS, L., P. (2003). Hippopotamids from the Djurab Pliocene faunas, Chad, Central Africa. Journal of African Earth Sciences 36, 15-27. CORYNDON, S.C. (1978). Hippopotamidae. In: Evolution of African Mammals (eds V.J. Maglio and H.B.S. Cooke). Cambridge, Harvard Univ. Press, 483-495.

WESTON, E., (2000). A new species of hippopotamus Hexaprotodon lothagamiensis (Mammalia: Hippopotamidae) from the Late Miocene of Kenya. Journal of Vertebrate Paleontology 20 (1), 177-185

Gaziry, A.W. (1987). Merycopotamus petrocchii (Artiodactyla, Mammalia) from Sahabi, Libya. In: Neogene Paleontology and Geology of Sahabi (eds N.T. Boaz, A. El-Arnauti, A.W. Gaziry, J. de Heinzelin and D. Dechant Boaz). Liss, New York, 303-315. LAWS, R.M. (1968). Dentition and aging in Hippopotamus. E. Afr. Wildl. J. 8, 19-52. LIHOREAU, F., Boisserie, J.-R., Viriot, L., Coppens, Y., Likius, A., Mackay, H.-T., Tafforeau, P., Vignaud, P. and Brunet, M.

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Newly Discovered Remains of As Sahabi Anthracotheriidae

PARIS PAVLAKIS and NOEL T. BOAZ

ABSTRACT The cranial and dental anthracotheriid sample collected from As Sahabi, Libya, by the East Libya Neogene Research Project during 2007 is described. The partial skull 8P17C presents good evidence of this animal`s craniodental morphology, in particular the shape, number, relative location, and series of eruption of its 5 permanent premolars, as well as the morphology of the deciduous 3rd and 4th premolars. Two specimens collected by the Petrocchi expeditions in the 1930â&#x20AC;&#x2122;s and housed in the National Museum of Libya, Tripoli are described. All anthracothere fossils from As Sahabi are assigned to Libycosaurus petrocchii (Bonarelli, 1947).

Paris Pavlakis, Department of Historical Geology â&#x20AC;&#x201C; Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimioupoli Zografou, 157 84 Athens, Greece, pavlakis@geol.uoa.gr Noel T. Boaz, International Institute for Human Evolutionary Research, Integrative Centers for Science and Medicine, 2640 Takelma Way, Ashland, Oregon 97520, U.S.A., noeltboaz@integrativemedsci.org, and Department of Anatomy, Ross University School of Medicine, P.O. Box 266, Portsmouth Campus, Roseau, Commonwealth of Dominica, nboaz@rossmed.edu.dm

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part of the frontal portion of the braincase is shown on the internal surface of the left frontal bone. Both canines are just erupting from their sockets, the right somewhat in advance of the left. There is a small postcanine diastema. An accessory premolar, Px, is present. This is an a u t a p o mo r p h i c c h a r a c t e r i s t i c o f Libycosaurus (Pickford, 1991; Lihoreau et al., 2006). It is fully erupted on both sides, just distal to the point of the maximum mediolateral constriction of the maxillae. About 4/5ths of both P1/ crowns are erupted. dP2/ is shed from both sides, and the P2/s are still well inside the alveoli. dP3/ and dP4/ are still in place on both sides, but they are very worn. Both M/1’s are fragmented. dP/4 is substantially smaller than dM/1. (The teeth preserved in this and the two following mandibular specimens will be described separately along with the isolated dental material of the sample.) At the anterior and lateral part of the palate, at the level of P2/, a well developed tubular canal on either side is present. This canal or “tube” leads to a huge single incisive foramen, a characteristic of Libycosaurus petrocchii (Pickford, 1991). In frontal view the skull shows a wide area for the premaxillo-maxillary suture anteriorly to both canines, leading to a foramen and a groove. The hard palate exhibits anteriorly a deep long groove in the midline for the attachment of the vomer. Only the posterior parts of the nasals are preserved, with articulation between them as well as with the frontals. The lacrimal and jugal bones complete the orbit, which is open posteriorly. The orbits are located higher than the frontal bone.

INTRODUCTION A sizable anthracothere sample was collected during the first palaeontological field expedition to As Sahabi, Libya under the renewed East Libya Neogene Research Project (ENLRP). The field season took place from February 1st to March 3rd, 2007. Here we report on the cranial and dental material. DESCRIPTIONS Anthracotheriid Material 8P17C - Partial skull with right and left Px/, P1/, dP3/, dP4/ and part of M1/, (Lt P2/ is just erupting); 3P17C - Right mandibular fragment with P/4, M/1, M/2 and part of M/3; 4P17C - Right mandibular fragment with parts of right P/2, P/3, P/4, M/1 and M/2; 23P103A - Right P/1; 23P107A Left P/4; 16P28B - Right M/2 fragment; 58P24A - Right P3/; 9P16C - Left P3/; 16P38B - Right P4/; 27P14A, germ of Right ?M1/; 4P33C - Left M2/ fragment; 8P99B - Right M2/ fragment; 16P201A Left M3/ fragment Skull and Mandible Specimen 8P17C is a partial skull of a juvenile anthracothere (Figures 1, 2, and 3). In basilar view one observes the maxilla and part of the horizontal parts of the palatine bones, across the transverse palatine sutures. The opening of the left pterygoid fossa is preserved. At the back of the skull parts of both jugal and squamosal bones are present, forming most the right zygomatic arch. The mandibular fossae on both sides, as well as the left external acoustic meatus, are preserved. The anterior

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Figure 1. Right lateral view of specimen 8P17C, a Libycosaurus petrocchii partial skull from As Sahabi. The erupting canine is separated distally from Px by a diastema, followed by P1, P2, dp3,dp4 and part of M1. P3 and P4 have not yet erupted. Bar scale 1 cm.

Figure 2. Left lateral view of specimen 8P17C, a Libycosaurus petrocchii partial skull from As Sahabi. This is juvenile specimen preserving the deciduous fourth premolar with an emerging permanent P4 crown in its crypt. This specimen shows bilateral presence of five premolars. Top: a view of the specimen with a window of maxillary bone removed to expose the P3 and P4 in their crypts. Bar scale 5 cm. Below: Left lateral CT scan at the same scale with individual teeth identified.

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Figure 3. Occlusal view of cranium and maxillary of dentition of Libycosaurus petrocchii (8P17C). CT scan (above) and photograph (below) with individual teeth identified. Bar scale 5 cm.

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zygomatic arch to the median plane). Maximum width of the nasal bones at the interorbital level = 66.98 mm Minimum width of the nasal orifice = 40.46 mm Measurements in palatal view are: Maximum width of the palate at the level of the canines (at their tips) = 55.90 mm Maximum width of the palate at the extreme mesiolingual point of Pxs = 40.20 mm Maximum constriction (at the level of C-Px diastema) = 55.48 mm -Left C/ - Px diastema = 30.52 mm Maximum width of the palate at the extreme mesiolingual point of P1/s = 36.76 mm. Maximum width of palate at mesiobuccal angles of dP4/s = 90.50 mm Minimum width of palate at mesiolingual angles of dP4/s = 47.20 mm Specimen 3P17C is a right mandibular fragment with P/4, M/1, M/2 and the mesial half of M/3 broken at the mesostyle (Figure 4). The alveoli of P/2 and P/3 are also preserved. The body of the

The measured skull dimensions follow Pavlakis (1990) and the dentition dimensions follow Gaziry (1987). The measurements where taken by a Mitutoyo dial caliper (0.02 mm accuracy). The skull measurements in lateral view are: Height of the snout at the level anterior to right dP3/ = 88.24 mm Height of snout anterior to right M1/ (and orbit) = 88.74 mm Maximum height of the right orbit = 44.00 mm Elevation of the right supraorbital ridge over the right nasal bone at the nasofrontal suture = 20.40 mm Minimum height of the right zygomatic arch (in front of the articular fossa) = 23.64+ mm Antero-posterior diameter of the orbit = 50.12 mm Measurements in superior view are: Maximum width of the zygomatic arches = 111.28 X 2 = 222.56 mm (taken as double the distance of the right

Figure 4. Libycosaurus petrocchii mandibular fragments from As Sahabi: 4P17C right hemimandible fragment (above), and 3P17C right mandibular fragment (below). Buccal side. Bar scale 5 cm.

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Dentition

mandible is broken transversally at the level of the mental foramen, making it thus impossible to take any height measurement of the mandibular body. Measurements that can be taken are: Maximum thickness of mandibular body just mesial to M/1 = 30.44 mm Length of M/1 â&#x20AC;&#x201C; M3/ = 98.62 mm (estimated by doubling the maximum length of the preserved M/3 half). All teeth are extremely tightly packed together and show a high degree of interstitial wear and even overlapping. Specimen 4P17C is a right mandibular fragment with parts of P/2, P/3, P/4, M1/ and M/2 (Figure 4). The specimen preserves most of the right mandibular body, from the level of P/1 to the close to the mandibular angle. The mandibular ramus is broken at the level of M/3, the latter being absent. Only the M/3 alveolus is preserved. Both M/2 and M/1 are broken off and only their roots are preserved in their alveoli. P/2 to P/4 are also broken, with most of their lingual half missing. P/1 is presented by only its roots. Two mental foramina are present at the exterior surface of the mandibular body. The one at the level of P/2 measures about 1.5 cm length and 7.54 mm maximum width. The second, at the level just mesial to M/1, measures 5.22 X about 7 mm. Maximum height of the mandibular body at the level of the mesial edge of P/2 is 53.36 mm and at the level mesial of M/3 is 63.62 mm. Maximum width mesial to M/2 is 32.18 mm. Estimated length of the molar tooth row is 88.2 mm. The length of the premolar row measures about 84 mm. The flair at the mandibular angle measures 8+ cm anteroposteriorly and is located 5 cm lower than the rest of the mandibular body.

Upper Teeth â&#x20AC;&#x201D; Deciduous The following deciduous teeth are present in the anthracothere sample from As-Sahabi: Right and left dP3/, dP4/, all on the 8P17C partial skull (Figures 2, 3). (1) dP/3 is triangular in cross section (the apex located mesially), preserving three very worn lophs, separated by transverse styles. The two mesial lophs were single cuspid. The distal third probably had two cusps (Gaziry, 1987). The tooth has three roots. Dimensions are given in Table 1. (2) dP4/ presents a molariform occlusal area tooth pattern. The molariform pattern of dP4/ in Libycosaurus was evident from the previously collected As-Sahabi material (Gaziry, 1978, Fig. 4, p. 292), and first noted by Black (1972). It is rectangular in shape, being wider than longer. Both dP4/s are very worn and tightly packed between dP/3 and M1/. They show the typical tetracuspid selenodont anthracothere molar occlusal pattern, without, however, so deep a median transverse valley and strong cingulum around the cusps as the permanent molars exhibit. dP4/, besides being almost identical to M1/ (except for being about one third smaller in length and width than M1/), is different than the permanent P4/. Both P3/ and P4/ have entirely different morphology than their corresponding deciduous premolars (see Discussion). Dimensions are given in Table 1. Upper Teeth â&#x20AC;&#x201D; Permanent Both left and right upper canines on the 8P17C skull are just erupting, revealing only their tips from their small alveoli openings. The right alveolus is about 6 mm

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Table 1. Dimensions in mm, of Libycosaurus petrochii deciduous teeth sample from As Sahabi.

Want

Wpost

8 P17C Rt dP3/

24.08

12.10

19.82

8 P17C Lt dP3/

22.92

11.48

18.02

8 P17C Rt dP4/

21.22

22.50+

24.00

8 P17C Lt dP4/

20.22

23.00

22.68

the longest, having a less steep slope than the other three ridges. It bears 3 large tubercles on its ridge, instead of the 2 and much less pronounced tubercles shown on the Pxs. The tubercles decrease in size down the distal ridge. There is a weak buccal cingulum and a strong lingual cingulum, which becomes more pronounced distally.

in diameter, while the left canine alveolus is exposed laterally for about 1.5 cm. A feature of Libycosaurus,rare in Mammalia, is the possession of an accessory fifth premolar, the Px, clearly shown on the 8P17C partial skull (Figure 3). Both left and right Pxs are fully erupted (measurements in Table 2). They are unicusped with their long axis turning mesiolingually. The degree of such an orientation increases towards the last premolar (P4/), to make room for the unusual number of five premolars. The single cusp presents a steep mesial ridge and a more gradually sloping distal one. The latter is decorated with two denticulated tubercles right on the ridge. There is a weak cingulum all around the distal half of the tooth.

(2) The Lt P2/ is just erupting at the skull fragment 8P17C. It is more exposed laterally, revealing in essence the morphology of an enlarged P1/ in three dimensions. It is more vertically oriented to the teeth row than the P1/s. The distolingual side of the single cusp is steeper than the buccal. The mesio-buccal ridge is the longest (and less steep) of the four. It is decorated with extra cuspules or indentations, as is the pattern of all Libycosaurus anterior single-cusped premolars. The cingulum is stronger than that of P1/, both distobucally and especially distolingually.

(1) The P1/`s on the 8P17C skull show the typical Libycosaurus morphology, being single-cuspid with four well delineated crests. The apex of the protocone is tilted slightly lingually. The distobuccal crest is

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Table 2. Dimensions in mm of Libycosaurus petrochii premolar sample from As Sahabi. L

8 P17C Rt Px/

15.58

10.70

8 P17C Lt Px /

15.98

9.88

8 P17C Rt P1/

20.30

13.16

8 P17C Lt P1/

17.02

14.50

58P24A Rt P3/

31.20

27.84

9P16C Lt P3/

30.08+

25.22

16P88B Rt P4/

20.78

22.50

23P103A Rt P/1

17.72

12.68

4 P17C Rt P/2

21.08

4 P17C Rt P/3

22.96

3 P17C Rt P/4

23.18

16.72+

4 P17C Rt P/4

23.78

18.74+

23P107A Lt P/4

25.60

17.50

mesial. The highest cuspule on the distal ridge is clearly delineated by moderately deep valleys which run down from the protocone mesially, and from the lower cuspule distally. These reach the level of the cingulum. The buccal ridge of the protocone is razor sharp, and terminates vertically on the cingulum. The lingual side of the protocone cusp bears no ridge. The cingulum is well developed all around the tooth. It is much pronounced at the distolingual and mesiobuccal parts of the diamond-shaped tooth perimeter. In these two parts of the cingulum exist many indentations, covering parts of the two foveae located medially to the cingulum. Judging from the odd appearance of this

(3) Three P3/s are present in the sample: 58P24A, a right P3/, and 9P16C, a left P3/ , are isolated, while the 8P17C left P3/ (germ) has been artificially exposed laterally by an 1cm wide section over the left dP3/ and dP4/ area of the skull fragment. The P3/s are wider than P2/s, (see dimensions in Table 1). 58P24A is a fully grown, totally unworn unerupted right P3 (Figure 5). The fact that this isolated 3rd premolar bears no wear at all reveals its tooth morphology in every detail. The two ridges of the single cusp along the length axis of the tooth, the mesial and the distal, both carry a spectacular array of denticulations. There are three large ones on the distal ridge and three smaller on the

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Figure 5. 58P24A Libycosaurus petrocchii right P3/ from As Sahabi with characteristic indentations. Lingual side. Bar scale 1 cm.

(4) The P4/ is represented in the recent AsSahabi sample by specimen 16P88B,an isolated right P4/. In addition, the germ left P4/ has been exposed on the 8P17C partial skull. The latter verifies that the fifth permanent premolar, the P4/, is nesting inside the molariform dP4/. While the dP4 has a typically molar (i.e., tetracuspid selenodont) occlusal morphology, P4/ is bicuspid. Actually P4/ looks like a half molar. It has a trapezoid cross section with the smaller parallel side lingually. It is wider than long, and judging from the way the germ P4/ is sited inside the alveolus, it is not shifted mesiolingually like the rest of the premolars. Apparently, the bicuspid P4/ fits between the long single-cusped P3/

unworn premolar (Figure 5), one may sympathize with Bonarelli (1947) who, being tricked by these so many serrations, identified such teeth as belonging to a dinosaur. The artificially partially exposed P3/ on the skull fragment 8P17C documents the described morphology, as well as the increasing number of indentations (up to 5) on the serrated distal ridge. The corresponding deciduous tooth with the triangular shape is the dP3/ and the next molariform tooth distally is the dP4/. The substantially worn 9P16C left P3/ shows the two roots characteristic of the P3/s, as well as the concave wear pattern of the major (i.e., the distal) ridge.

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(5) M1/s are in situ in both sides of the 8P17C partial skull, but their crown areas are badly fragmented, so no accurate measurements can be taken. An estimate of left M1/ size is included in Table 1, for comparison with the molariform dP4/. 27P14A is the complete crown of a germ Rt M1/. Given that it is a germ tooth, 27P14A is possible that it can be a 2nd molar. The entire crown is lacking any wear, so the molar morphology of the occlusal surface can be seen in full detail (Figure 6). It bears four cusps: protocone (mesiolingually), paracone (mesiobuccally), metaconule (distolingually, called hypocone by Gaziry, 1987) and metacone (distobuccally). In cross-section, the molars are square, with the mesial half wider and more lingually positioned than the distal half. The protocone is larger than the metaconule, consequently the anterolingual molar root is larger than the posterolingual (contra

anteriorly and the large square-shaped M1/ posteriorly, by becoming shorter and wider, a common solution for P4/s, seen also in hippos (Pavlakis, 1990). The two cusps are well-developed, and the whole crown is tilted slightly anteriorly (a useful character for orienting isolated P4/s). The protocone is located lingually and is slightly smaller than the buccal paracone, a cusp which Gaziry (1987) called a metacone. Strong ridges leave the apices of both cusps, one mesio- and the other disto-bucally, ending on the strong cingulum. Those of the protocone end in the midline, thus raising the rim of the cingulum even higher. The two ridges of the paracone end bucally, each one on an accessory cuspule, before looping around the mesial ridge anteriorly and the distal posteriorly to meet the cingulum, exactly like the S-shape looping of the buccal ridges and the cingulum, seen in the molars. The tooth bears two roots.

Figure 6. 27P14A, a Libycosaurus petrocchii upper ?right first molar germ from As Sahabi. Scale 1 cm.

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anteriorly these cutting ridges to the serrated longitudinal ridges of the five premolars all the way to the canines and the anterior dentition, we realize that we are dealing in Libycosaurus with an extremely efficient food-cutting and grinding machine, whose adaptational and paleoecological dimjensions are not yet fully understood.

Gaziry, 1987:295). The occlusal pattern is clearly selenodont, with two sharp ridges leaving each of the four cusp apices, the one going mesiobucally and the other distobucally. The transverse valley is straight and cuts the molar deep in half, to the level of the cingulum. The longitudinal valley is much shallower than the transverse. It consists of two semicircles, delineating the concave buccal aspect of protocone and metaconule. The cingulum is strong mesially and distally and in both cusps, its buccal half is incorporating the outer ridges of protocone and metaconule, thus doubling their size. The buccal ends of the adjacent ridges of paracone and metacone create a loop like strong mesostyle, while the distal and mesial ridges form a parastyle and a metastyle. These three styles fill the gaps of a continuous sharp edge that runs buccally in all three upper molars. Now, if we add to this continuous sharp edge the second cutting line of the molars, located lingually to the first, and mostly if we expand

(6) The M2/s sample consists of two isolated permanent teeth: 4P33C a left M2/ missing the mesial part anteriorly to the protocone and metacone apices, and 8P99B a right M2/ missing a flake of its protocone (mesiolingually). Basically M2/s represent a non-allometric size increase over the M1/ morphology. They are simply bigger than M1/s. The mesial and distal cingula in M2/s have the same thickness throughout their lengths. (7) Specimen 16P201A is a left M3/. It is recognised from its large size (Table 3).

Table 3. Dimensions in mm of Libycosaurus petrochii molar sample from As Sahabi. L 8 P17C Lt M1/

tr1

27.38+

30.80+

27P14A germ Rt ?M1/ 30.48

tr2

tr3

31.26 30.98 31.02

4P33C Lt M2/ frag.

32.68 34.98

8P99B Rt M2/ frag.

34.58

35.64

32.00 34.10

16P201A Lt M3/ frag.

39.82+

46.64+ 42.76 47.32

3 P17C Rt M/1

23.36

15.98

3 P17C Rt M/2

39.96

23.40+ 22.78 24.56

16P28B Rt M/2

32.52

21.00+ 21.14 23.04

3 P17C Rt M/3 frag.

44+

26.28 199

14.14 15.60

25.10

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Lower Teeth

left P/4, 23P107A, one right on the 3P17C mandibular fragment with damaged its lingual surface, and a right P/4 on the 4P17C right mandibular fragment, missing almost half of its mesial part. P/4 presents the typical trigonid and talonid occlusal tooth morphology. The trigonid anteriorly bears three well-developed cusps, the larger protoconid bucally, the paraconid mesiolingually and the metaconid distolingually. The paraconid is equal size to metaconid. The descending mesial protoconid ridge is completely united since halfway with the descending buccally mesial paraconid ridge, thus outlining the mesial rim of a deep intratricuspid fovea. The distal protoconid ridge continuous lingually leaving the mesoconid anteriorly. It ends on the lingual cingulum creating thus another small valley distally to mesoconid, with its distobuccal and distolingual ridges. The trigonid measures 8.58 mm maximum length and has a strong cingulum distally bearing three cuspules on it. The anterior cingulum is also strong and serrated. On the mesial ridge of the paraconid there is one large indentation lower on the ridge. P/4 has two roots. On 3P17C right mandible, the P/4 is squeezed between P/3 and M/1.

(1) An isolated right P/1, 23P103A,is

single-cusped, with subrectangular cross section at the crown base. The large protoconid cone is concave lingually and convex buccally. It exhibits a wear facet distally, which ends on a small talonid. The cusp has two ridges lingually, one mesial and the other distal, as well as one distal ridge buccally. The lingual ridges are serrated. The mesial bears two cuspules, and the distal one. The cingulum is stronger lingually. P/1 has two roots. Another P/1 is preserved only by its roots in situ on the mandibular fragment 4 P17C. It is followed by three more premolars distally. (2) A fragmented right P/2 missing almost half its lingual crown is present on the 4 P17C Rt mandibular fragment. It shows the unicuspid, subrectangular cross section and the convex bucal cusp surface form of the P/1. The talonid is larger than in P/1, but substantially smaller than in P/3. It bears small cuspules on its rim. (3) The 4P17C right mandibular fragment preserves the Rt P/3, missing the buccal 1/4th of its crown. It has one large cusp, the protoconid, but it is more rectangular in cross section than P/1 or P/2. The talonid measures 6.52 mm in length and is larger than the talonid in the premolars anterior to it. The cingulum is more developed mesially and buccally than in the anterior premolars, bearing also a larger cuspule on its midline.

(5) 3P17C and 4P17C right mandibular fragments preserve right M/1s. The former is complete, while the latter is broken from its roots. 3P17C is rectangular in cross section. It is worn out extensively. It has four roots. (6) Specimen 16P28B is a complete isolated right M/2 with minimum wear. In addition, on the mandibular fragment 3P17C there is in situ a complete M/2 with a medium

(4) There are 3 P/4s in the recent As Sahabi anthracothere sample: a complete isolated

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and P4/ we verified the following anatomy. Distal to the premaxillary-maxillary suture the first erupting tooth is the canine, followed by a diastema and by four unicuspid serrated premolars (Px/-P3/). The premolars increase distally in size and diagonal position relative to the mesialdistal axis. P4/ is triangular in cross-section with the apex located lingually. The dP3/ is tricuspid and triangular in cross-section with the apex located mesially. The dP4/ is molariform with four cusps in a typical selenodont molar occlusal configuration. The specimen Bonarelli named Libycosaurus petrocchii is a very similar skull fragment to 8P17C (Bonarelli, 1947, Fig. 1, p. 25). It is a juvenile skull and preserves four unicuspid strongly serrated premolariform teeth and two tetracuspid molariform teeth. It presents the tooth row Px/-M2/ (Lihoreau, et al., 2006, Supplement) instead of the C/-M1/ present in 8P17C. The first tooth in the holotype is the Px/ and not the C/, since there is no diastema with the adjacent premolar distally, as opposed to the teeth series in 8P17C. Black in 1972 came close to recognising Libycosaurus as a valid anthracothere genus â&#x20AC;&#x153;were it not for the intermediate [to Merycopotamus] Tunisian sampleâ&#x20AC;? (Black, 1972:25). Based on the then known anthracothere material from As Sahabi, he noted that it differs from the Asian Merycopotamus by presenting bigger and more serrated upper premolars, molars with a rounded mesostyle labially formed by the paracone â&#x20AC;&#x201C; metacone crest, and high V-shaped molar cusps without protoconules. He referred the As Sahabi anthracothere material to an African species

amount of wear. On the right mandibular fragment 4P17C only the roots of the M/2 are preserved. M/2 is rectangular in cross section, and the occlusal surface bears four cusps. The protoconid and hypoconid, the two buccal cusps, show greater degree of wear than the lingual (Med, Entd). The buccal cusps have a V-shaped wear facet, while the lingual cusps preserve their cones as on specimen 16P28B, or show a much smaller wear facet as on 3P17C. The transverse valley is deep bucally but is substantially higher and shallower lingually. There is a cingulum anteriorly, bucally and posteriorly, but not lingually. The transverse valley ends bucally on a developed cingulum with cuspules. (7) Specimen 3P17C is a right mandibular fragment which preserves only the anterior part of the M/3 to the transverse valley. It is less worn than M/2, the anterior cingulum is stronger than on the M/2 and it is larger than the M/2. DISCUSSION The anthracothere cranial sample described here offers valuable information to the systematics of the Anthracotheriidae from As Sahabi. The partial skull 8P17C in particular, presents dental and cranial morphology that firmly identifies it as Libycosaurus petrocchii (Bonarelli, 1947). Furthermore, it presents definitive evidence of its dental formula, especially the number of premolars it possesses and the replacement of deciduous teeth by permanent dentition (Figure 3). From a CT scan of 8P17C and subsequent exposure of the left buccal aspect of the non-erupted P3/

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species and the specimens fall at the low end of the range of variation of the L. anisae sample from the Beglia Formation (Late Miocene, ca. 12-11 ma, from eastern Tunisia). He considers it likely that L. algeriensis is a synonym of L. anisae. The youngest species is L. petrocchii (Late Miocene of As Sahabi and Chad). It falls above the known range of variation of L. anisae in almost all metric features. L. petrocchii is here considered to represent a distinct species from the Beglia sample, larger but similar in morphology. On the matter of five premolars, Pickford (1991) first recognised the series of five premolars in L. anisae (Tunisia) and L. petrochii (Libya and Chad). He reported that “in every specimen in which the appropriate part of the maxilla is preserved, it is evident that Libycosaurus possessed five upper premolars” (Pickford, 1991:1519). In a note, however, added in proof, he stated that the anteriormost of these five premolariform teeth is the canine. While the priority of Libycosaurus over Merycopotamus for the North African anthracotheres was established by Pickford in 1991, the confusion over the number of upper premolars remained. Pickford (1994) still considered the anteriormost of the five premolariform tooth as the canine. Lihoreau, et al. (2006) established the presence of five premolars based on microtomographic analysis. The L. petrocchii 8P17C cranium offers information that decisively clarifies the number of premolars, the sequence of permanent tooth eruption, the replacement of deciduous with permanent teeth, and that the first tooth that erupts distally to the premaxillary -maxillary suture is the canine.

of Merycopotamus, a younger descendent of the Late Miocene Tunisian Merycopotamus anisae, using the taxon “Libycosaurus” petrocchii (Black, 1972). In his 1978 review of the Anthracotheriidae, Black referred the As Sahabi antheracothere to Merycopotamus petrocchii (Bonarelli, 1947), and used Libycosaurus petrocchii as a synonym (Black, 1978). Gaziry (1987) also referred new anthracothere material recovered at As Sahabi by the ISRP to Merycopotamus petrocchii. Pickford (1991:1515) in his revision of the Neogene Anthracotheriidae of Africa, formally recognised the genus Libycosaurus as a large anthracothere with four-cuspidate upper molars in which the loop-like mesostyles are undivided. L. petrochii was characterised as a large anthracothere species with four-cuspid upper molars, in which the mesostyle forms a prominent loop. He included in this taxon the then known As Sahabi material, as well as undescribed skull fragments and a mandible from Chad (Coppens, 1972). Later, in 2002, Libycosaurus petrochii was recognised in Chad, at Toros Menalla, in the middle section (Anthracotheriid Unit), along with Sahelanthropus tchadensis and a terrestrial vertebrate faunal sample (Vignaud, 2002; see Boaz, this volume). A new Libycosaurus species (in addition to L. petrocchii and L. anisae), L. algeriensis of Middle Miocene age from eastern Algeria, was established by Ducrocq, et al. (2001). Recently, Pickford (2006) examined the morphometric variation of the available Libycosaurus samples. L. algeriensis (Middle Miocene of Nementcha, eastern Algeria) is the older

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BLACK, C. (1978). Anthracotheriidae. In: Evolution of African Mammals (eds V. Maglio and H.B.S. Cook) . Harvard Univ. Press, 423-434.

It presents non-serrated contour ridges, and a distally curved long axis, as is also shown on the palatal view of specimen 2P24A (Gaziry, 1987:293, Figure 6). Further information about the morphology of L. petrocchii, such as size range and sexual dimorphism, is expected to result from the analysis of the new postcranial anthracothere sample from As Sahabi following this study. This will further clari fy t he speci es’ taxonomy, biochronology, and palaeoecology.

BONARELLI, G. (1947). Dinosaurio fossile del Sahara Cirenaico. Riv. Biol. Colon. Roma, 8, 23-33. COPPENS, Y. (1972). Tentative de zonation du Pliocene et du Pleistocene d’Afrique par les grands mammiferes. Comptes Rendus de l’Academie des Sciences 274, 181-184. DUCROCQ, S., COIFFAIT, B., COIFFAIT, P.E., MAHBOUBI, M. and JAEGGER, J.J. (2001). The Miocene Anthracotheriidae (Artiodactyla, Mammalia) from the Nementcha, eastern Algeria. N. Jb. Geol. Paläont. Mh. 2001(3), 145-156.

ACKNOWLEDGMENTS Prof. K. Tsiklakis, Director of the Oral Diagnosis and Radiology Clinic of the University of Athens School of Dentistry, and assistant N. Alexiou performed a complete CT Scan of the skull 8P17C. D. Michailidis, doctoral student, Department of Paleontology, University of Athens, restored the skull 8P17C. The members of the Department of Geology, University of Garyounis, made the 2007 As Sahabi field season possible. Research was supported by NSF grant BNS to B. Benefit, M. McCrossin, and N.T. Boaz, New Mexico State University; subcontractor, P. Pavlakis, University of Athens.

GAZIRY, A.W. (1987). Merycopotamus petrocchii (Artiodactyla, Mammalia) from Sahabi, Libya. In: Neogene Paleontology and Geology of Sahabi (eds N.T. Boaz, A. El-Arnauti, A.W. Gaziry, J. de Heinzelin and D. Dechant Boaz). Liss, New York, 287-302. LIHOREAU, F., BOISSERIE, J.-R., Viriot, L., COPPENS, Y., LIKIUS, A., MACKAY, H.-T., TAFFOREAU, P., VIGNAUD., and BRUNET, M. (2006). Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince. PNAS 103(23), 8763-8767.

REFERENCES BLACK, C. (1972). A new species of Merycopotamus (Artiodactyla: Anthracotheriidae) from the Late Miocene of Tunisia. Notes Serv. Gėol. Tunisia 37(2), 5-39.

PAVLAKIS, P.P. (1990). Plio-Pleistocene Hippopotamidae from the Upper Semliki. Virginia Mus. Nat. Hist. Memoir 1, 203223.

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PICKFORD, M. (1991). Revision of the Neogene Anthracotheriidae of Africa. In: The Geology of Libya (eds M.J. Salem, O.S. Hammuda and B.A. Eliagoubi). Elsevier, Amsterdam, IV, 1491-1525. PICKFORD, M. (1994). Anthracotheriidae from the Albertine rift valley. In: Geology and Palaeobiology of the Albertine Rift Valley Uganda-Zaire, Vol. II: Palaeobiology (eds B. Senut and M. Pickford). CIFEG, Occas. Publ. 1994 (29), 309-319. PICKFORD, M. (2006). Sexual and individual morphometric variation in Libycosaurus (Mammalia, Anthracotheriidae) from the Magreb and Libya. Geobios 39, 267-310. VIGNAUD, P., DURINGER, P., MACKAYE, H.T., LIKIUS, A., BLONDEL, C., BOISSERIE, J.-R., DE BONIS, L., EISENMANN, V., ETIENNE, M.-E., GERAADS, D., GUY, F., LEHMANN, T., LIHOREAU, F., LopezM ARTINEZ , N., M OURER -C HAUVIRĂ&#x2C6; , OTERO, O., RAGE, J.-C., SCHUSTER M., VIRIOT, L., ZAZZO, A., and BRUNET., M. (2002). Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature 418, 152-155

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Special Issue, No. 5

New Records of Bovidae from the Sahabi Formation ALAN W. GENTRY

ABSTRACT New bovid fossils from the Sahabi Formation are described. They are ascribed to the boselaphine Miotragoceros cyrenaicus, the reduncine Kobus aff. subdolus, and the hippotragine ?Hippotragus sp. There are currently 8 bovid taxa recognised from As Sahabi. There is an indication that the known bovid sample from As Sahabi derives from two different ages, suggesting that two stratigraphic levels have been sampled – the lower Member U sample collected since the 1970’s and a younger sample collected in the 1930’s, presumably from Members U-2/V. This latter sample includes “Leptobos” syrticus, which to date has not been collected in lower Member U localities, and the type specimen of Miotragoceros cyrenaicus, which is more advanced than a recently discovered skull from Member U-1, described here.

Alan W. Gentry, Department of Palaeontology, Natural History Museum London, Cromwell Road, London SW7 5BD, U.K.

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diverging horn cores, backwardly curved and without a demarcation along their preserved length. A demarcation in boselaphine bovids is where the top of the anterior keel finishes and the distal part of the horn core continues with a sometimes abruptly reduced anteroposterior diameter. A fine cranium from the Baynunah Formation of Abu Dhabi, United Arab Emirates, (Gentry, 1999, figs. 22.5-22.8) has widely diverging and backwardly curved horn cores like the holotype of M. cyrenaicus but also has more lyration and more of a drawn-out demarcation. Gentry assigned it to M. cyrenaicus. Miotragocerus acrae of the earliest Pliocene of Langebaanweg, South Africa, is a species of about the same size as the As Sahabi and Abu Dhabi fossils. Other late Miocene to Early Pliocene Miotragocerus from East African localities have been compared with M. cyrenaicus in varied “aff.” nomenclatural combinations. One from Lothagam, Kenya (Harris, 2003: 537, figs. 11.5-6) has smaller, longer, less compressed and less divergent horn cores than in M. cyrenaicus, but could easily be closely related or a conspecific regional variant. A similar form in the Adu-Asa Formation has more compressed horn cores and a stronger anterior keel (Haile-Selassie et al., 2004). Smaller Miotragocerus from Lothagam and Dytiko, Greece (Harris, 2003, figs. 11.7-8; Bouvrain, 1988), suggest that one or more smaller species also survived into this period. 10P103A is a new find at As Sahabi of parts of a skull with the left horn core, index ca.76×36.1, length ca.280 (front) or ca.240 (back) (Figure 1). The base of the broken right horn core suggests an anteroposterior diameter of 80-90 mm. Right and left joined M2-3 are in early

The bovids hitherto known from As Sahabi may be listed below. This paper records and briefly reports on new material of the asterisked species. Boselaphini: *Miotragocerus cyrenaicus Thomas 1979 Bovini: Gen. indet., “Leptobos” syrticus Petrocchi 1956 Neotragini: Raphicerus sp. Lehmann and Thomas 1987 Antilopini: Gazella sp. Lehmann and Thomas 1987 Dytikodorcas libycus (Lehmann and Thomas) 1987 Reduncini: *Kobus aff. subdolus Gentry 1980 Hippotragini: *?Hippotragus sp. Lehmann and Thomas 1987 Alcelaphini: cf. Damalacra Lehmann and Thomas 1987 Miotragocerus cyrenaicus Miotragocerus was common in the Late Miocene of southeastern Europe, southwestern Asia and the Siwaliks. Its nomenclature is complicated and the course of speciation incompletely understood. Horn cores of advanced species of Miotragocerus show or tend to show longer horn cores, backward curvature, flattening of their lateral surfaces, the level of maximum transverse width lying more posterior than centrally, more of an approach to a posteromedial bulge or corner, greater divergence and a higher transverse ridge between the horn bases. Miotragocerus cyrenaicus fits the criteria for an advanced and later species. As described by Thomas (1979: 268, pl.1, fig. 5) it was based on a frontlet in the Rome collection. It is a large Miotragocerus with

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Figure 1. 10P103A, a partial skull with horn cores ascribed to Miotragocerus cyrenaicus. A. anterior view. B. dorsal view. C. lateral view.

Figure 2. 10P103A, ascribed to Miotragocerus cyrenaicus. A. right maxillary dentition, M2-3. B. left maxillary dentition, M2-3. middle wear (Figure 2). Their occlusal lengths and widths are M2 25.0×17.8, M3 24.0×15.9. The horn core is short and mediolaterally compressed. The index is 45%, where the index is (lateromedial diameter × 100) ÷ anteroposterior diameter, and this particular reading is based on the mean of the right and left anteroposterior

diameters. The maximum transverse width lies posteriorly, the lateral surface is flat with an anterior keel, probably a posterolateral keel and also an approach to a posteromedial keel. The horn core is almost curved backwards basally, but the posterior edge remains almost straight in side view. The demarcation can be seen

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probably less wide and the tips less curved forwards than in M. acrae. The teeth (Figure 2) are the first upper molars to be found of Miotragocerus cyrenaicus. They are moderately hypsodont and have rugose enamel. Styles on the upper molars are quite well shown. A labial rib is better developed on the paracone than on the metacone which has a slight convexity of its cross section. There is a low and narrow basal pillar near the base of each molar. The right M2 shows a very faint cingulum, the lingual lobes are bluntly pointed, a character most obvious on the front of M2, the lingual lobes remain unjoined to one another or to the labial side of the tooth, the central fossettes do not have a complicated outline. These teeth are of the same size and very similar to teeth of Miotragocerus acrae. They are perhaps slightly larger than teeth of M. amalthea, agreeing in this with the size of an As Sahabi mandible of M. cyrenaicus (Lehmann and Thomas 1987, fig. 1A). There is no reason why the cyrenaicus-acrae species or species-pair should not be a direct end-Miocene or Miocene-Pliocene development from an ancestor like the long known M. amalthea of Pikermi, Greece (MN12), itself probably a later variation of or from M. rugosifrons. The new skull seems to be about the same size as M. amalthea of Pikermi and the only discernible difference is that the upper teeth are slightly larger than most amalthea. Miotragocerus acrae, the M. cyrenaicus holotype and the Abu Dhabi cranium all have greater divergence than M. amalthea, but the Lothagam Miotragocerus aff. M. cyrenaicus does not. Further analysis will be needed to sort out the classification of these species. Perhaps the As Sahabi

and took the form of a series of steps, probably three, along the front edge. The degree of divergence lessens distally. A slight torsion is detectable which would have been anticlockwise on the right (= heteronymous or normal torsion). Sinuses were present in the frontals, pedicel and base of the horn core. The frontals were elevated between the horn bases and the cranium shows strong temporal ridges with a rugose surface between them. The new horn core is about the size of the M. cyrenaicus holotype but would have been shorter when complete, has more basal compression, has a demarcation, is less backwardly curved, and perhaps would have had more diminution of the degree of divergence distally. The strong anterior keel and the demarcations are at variance with previous As Sahabi horn cores (Lehmann and Thomas,1987: 326). It differs from the Abu Dhabi specimen by being shorter, more compressed, with a demarcation and less curved. The divergence is probably less wide and the tips less curved forwards than in the Abu Dhabi specimen. Miotragocerus acrae has horn cores with no backward curvature and usually less compression than in the North African and Arabian fossils. It would be expected that older individuals within any species would have greater anteroposterior diameters of their horn cores and thus acquire more compression, but there are no obvious signs that M. acrae horn cores are predominantly from younger individuals. The horn cores of M. acrae also tend to look shorter (not borne out by measurements), perhaps because of the lack of backward curvature and because the demarcation is lower and more localised. The divergence of our new horn core is

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species is really M. acrae and the Abu Dhabi cranium a different species, in which case the name cyrenaicus would be a junior synonym of acrae and the Abu Dhabi species in need of a new name. Perhaps the new As Sahabi specimen described here is either amalthea or from a lower stratigraphic level (U-1) than the cyrenaicus holotype, probably Member V (see Boaz, et al., this volume). For the present I refer it to M. cyrenaicus.

Langebaanweg and much bigger than extant species. Gazella sp. Lehmann and Thomas (1987, fig. 4C) based this species on two horn cores and a number of postcranial bones. Dytikodorcas libycus Dytikodorcas libycus was described under the name Prostrepsiceros libycus by Lehmann and Thomas (1987: 330, fig. 7AE). Prostrepsiceros Major 1891 is a Turolian genus of spiral-horned Antilopini. Through much of the twentieth century Prostrepsiceros and its relatives were regarded as Tragelaphini, but towards the end of his life Pilgrim began to correct this opinion (Pilgrim 1939, Pilgrim & Schaub 1939). There can be no doubt that Prostrepsiceros is close to the ancestry of Antilope cervicapra, the living Indian blackbuck. The As Sahabi representative was notably large, with weakly to moderately lyrated horn cores showing strong longitudinal grooves posteriorly and sometimes a shallow longitudinal groove on the front surface. Bouvrain and Bonis (2007) reallocated P. libycus to Dytikodorcas, a genus they had founded for a new gazelle-sized species Dytikodorcas longicornis from Dytiko 3, Greece, Late Miocene (MN13). Dytikodorcas libycus differed from D. longicornis by its much larger size and shorter horn pedicels. The generic name change for the As Sahabi species may be beneficial in that D. longicornis has very similar horn cores and is more nearly contemporaneous with the As Sahabi species. The closest

Gen. indet., â&#x20AC;&#x153;Leptobosâ&#x20AC;? syrticus This was described as Leptobos syrticus by Petrocchi (1956: 231, figs. 1-7) on three crania. It has been the most puzzling bovid to emerge from As Sahabi. Geraads (1989) asserted that it was not a Leptobos and must be of an age later than terminal Miocene. It is characterised by the striking specialisation of very large horn cores emerging almost transversely from the frontals. This must have imposed linked changes on other parts of the skull. The cranial roof became horizontal, the frontals did not become at all raised between the horn bases, the dorsal orbital rims project, presumably to compensate for the horn bases obstructing vision so close behind, and the temporal ridges are strong, presumably to brace the weight of the horn cores. The supraorbital pits, however, remain close together. Raphicerus sp. Lehmann and Thomas (1987, fig. 1D, E) based this species on a horn core, mandible and appropriately sized postcranial bones. The horn core, and perhaps the mandible too, were about the size of the smallest R. paralius at

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did not resemble sub-Saharan African reduncines and suggested descent from the As Sahabi reduncine. 1P98A (Figure 3) is a new find of the dorsal parts of a skull, hornless in life, consisting of top of right orbit and supraorbital pit extending to left frontal, back of nasals and top of right preorbital fossa;occipital plus basioccipital; right and left maxillae and mandibles with complete tooth rows in late middle wear (Figure 4). Tooth measurements are: P2-M3. P2-4 31.0, P2 10.5×7.4, P3 10.1×9.2, P4 9.8×11.8, M1-3 44.0, M1 11.7×15.3, M2 15.0×15.9, M3 16.9×14.4. P2-M3. P2-4 26.1, P2 7.1×4.3, P3 9.7×6.1, P4 10.4×6.6, M1-3 49.2, M1 12.3×9.9, M2 15.1×10.6, M3 22.1×10.2, ramus depth below P2 20.1, below M1 24.1, below M3 27.5. Being hornless in life this individual would have been a female, as in all reduncines. The preorbital fossa is large, the infraorbital foramen is positioned above the front half of P2, and the basioccipital is quite short. The modestly sized tuberosities of the basioccipital are again appropriate for a female animal. The auditory bulla is inflated but not greatly enlarged. The mastoids are moderately large, the nuchal crests are not smoothly rounded, and the occipital surface mostly faces backwards but has a median vertical ridge in its upper part. The anterior end of the mandible is scooped out immediately behind the incisors. The teeth (Figure 4) are moderately hypsodont, and enamel is rugose at least on the lower teeth. On upper molars there are no basal pillars, no cingula anterolingually or posterolingually, the styles are not overprominent, the labial rib on the paracone is

Prostrepsiceros to the As Sahabi species had been the Samos P. fraasi (Andree, 1926, pl. 15 fig.1) which was closer in size to D. libycus but more different morphologically and probably from an earlier time in the Turolian. Kobus aff. subdolus Kobus aff. subdolus was described under the name Redunca aff. darti by Lehmann and Thomas (1987: 327, figs. 9B,C). Their careful analysis suggested to them a generic identity with Redunca whereas Gentry (1980, 1997) believed that As Sahabi and Manonga reduncines had only minimal differences from his own K. subdolus (Gentry, 1980: 248, figs. 18-19, 23-25) from Langebaanweg. The As Sahabi species has short to moderately long and rather heavily-built horn cores, little compressed, with some indication of transverse ridges, with a flattened lateral surface, their widest mediolateral diameter lying centrally or rather anteriorly and the cross section narrowing behind to a posterolateral angle, with intermittent deep longitudinal grooving, inserted above the back of the orbits and close together, moderately strong divergence, only slightly curved backwards, well-inclined backwards, supraorbital pits possibly large, and cranial roof steeply angled. The horn cores are longer and more divergent than those at Langebaanweg. Kobus barbarus Geraads and Amani (1998: 194, figs. 3C-D) from the Late Pliocene of Ahl al Oughlam has large and long horn cores, not compressed in either direction, inclined backwards and divergent, slightly curved backwards, and with a suggestion of a posterolateral keel. The authors thought it

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Figure 3. 1P98A, a partial skull with dentition ascribed to Kobus aff. subdolus. A. dorsal view of the frontal. B. lateral view of the right maxilla and mandible

Figure 4. 1P98A ascribed to Kobus aff. subdolus. A. maxillary dentition. B. mandibular dentition. central fossette on P3 is placed anteriorly, there is only a shallow lingual indentation in the wall of P3 and it is not definitely there at all on P2, the labial rib of P2 and P3 is slightly anterior. On the lower molars the labial lobes are not sharply pointed, the lingual lobes are little outbowed, no metastylids remain visible, a hint of a goat fold on M3 could have been more

strong, there is no sign of flattening or a concavity on the metacone labial wall, and there is little sign of narrowed tips to the lingual lobes. The premolar rows are notably short in relation to the molar rows (53% according to the ratio [length lower premolar row Ă&#x2014; 100] Ăˇ length lower molar row). Nevertheless the length of each upper The premolar declines from P2 to P4.

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prominent in earlier wear, small basal pillars can be present, the presence or absence of a central fossette on the hypoconulid of M3 is not ascertainable. On the lower premolars there is some differentiation of parastylid and paraconid on P3 and P4, the P4 hypoconid projects labially but not very strongly, the P2 is relatively small. I1 and I2 are larger than I3 and the canine and I1 would probably have been relatively larger in earlier wear. This fossil can be identified as reduncine on the basis of a larger size than would be expected for a gazelle, hornless females, the narrow back of the nasals, and the absence of any consistent trend towards aegodonty or boödonty of its teeth. The basal pillars have diminished slightly from a presumed ancestral state but the anterior premolars have remained or become larger. The size is smaller than the supposed Dytikodorcas P4-M3 at As Sahabi (Lehmann and Thomas, 1987, pl. 2, fig. 4), the narrow nasals are unlike Antilopini but the basioccipital and large mastoids would fit. The premolar rows would be very short for a Miocene gazelle and are as short as in living gazelles. There are many differences from modern Reduncini. The ethmoidal fissure is absent or much smaller, the mastoid is relatively large, the basioccipital is quite short compared with K. kob, and without any transverse constriction behind the anterior tuberosities, the bulla is less strongly inflated. The new As Sahabi dentitions are unlike those of the Langebaanweg reduncine in several respects. They look more robustly built, with more rugose enamel, less flattening of the lingual walls

of the lower molars, shorter premolars rows (53% against a mean of 60% for four specimens), and shorter P2s and P3s. They agree better with reduncine teeth at Manonga described under the name Kobus aff. subdolus and which differed from Langebaanweg in stronger labial ribs and more complex central fossettes on upper molars, and in the stronger basal pillars, goat folds and outbowed lingual lobes of lower molars. The Manonga species may also have had a shorter premolar row and a more projecting hypoconulid on P4. ?Hippotragus sp. ?Hippotragus sp. was described on an As Sahabi horn core very like H. equinus in its backward curvature and some compression, but nearly a third smaller (Lehmann and Thomas, 1987, fig. 4a). A hippotragine frontlet and some teeth from the early Late Miocene of Djebel Krechem were thought to be the earliest in Africa (Geraads, 1989, pl. 2 fig.1, textfig.3a). The frontlet looks similar to Hippotragus bohlini from the Pinjor Formation of the Siwaliks (Pilgrim, 1939, pl. 2 figs. 3-6, textfig. 6; Gentry, 2000, fig. 5.3). 34P65A (Figure 5) is a newly found right mandible with P3-M3 in middle or late middle wear. Its measurements are: P3-M3. P2-4 c.38.0, P3 13.4×7.0, P4 14.8×9.0, M1-3 74.9, M1 19.5×12.4, M2 23.9×13.0, M3 32.4×12.0, ramus depth below P2 30.8. The lower molars have a somewhat squared-off appearance giving a hint of massiveness. Their lingual walls show slight outbowings and are flatter than in the reduncine dentitions. There are small basal pillars on M1 and M2 but not on M3; that on

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B Figure 5. 34P65A, a right hemi-mandible ascribed to ?Hippotragus sp. A. occlusal view. B. lateral view. crests, and flatter lingual walls, the short premolar row, P3 and P4 with less differentiation of paraconid and parastylid, P4 with the posteriorly positioned junction of the metaconid with the rear crest of the protoconid, and with the lingual end of the metaconid ridge in P4 being without anterior and posterior flanges. It is about the size of Samos Pachytragus laticeps but the molars look more bulky and the premolar row is again probably too short. Most probably it is of the Hippotragus already recorded for As Sahabi, in which case the shortness of the premolar row is a notable contrast with the two living species.

M2 is tall and narrow. A metastylid is present on M3, smaller on M2 and absent on M1, so it seems that it must disappear in later wear. The M3 has a hint of a goat fold and the lingual wall of its third or hypoconulid lobe is offset and the lobe has no central fossette. The premolar row is short (49% of the length of the molar row). The premolars show incomplete differentiation of paraconid and parastylid. On P3 and P4 the metaconid connects with the labial side of the tooth at a level posterior to the protoconid This mandible is not a boselaphine because of the molar characters of smaller basal pillars, earlier fusion of the crescentic 213

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REFERENCES

cf. Damalacra This species was based on a horn core (Lehmann and Thomas, 1987, fig. 4B) held to be like the Langebaanweg Damalacra acalla, but which had a keel and was more compressed than usual in that species. Other early fossils in North Africa have been attributed to Damalacra so this provisional generic identification may well be correct.

ANDREE, J. (1926). Neue Cavicornier aus dem Pliocän von Samos. Palaeontographica 67 (6), 135-175.

CONCLUSIONS

BOUVRAIN, G. and DE BONIS, L.. (2007). Ruminants (Mammalia, Artiodactyla: Tragulidae, Cervidae, Bovidae) des gisements du Miocène supérieur (Turolien) de Dytiko (Grèce). Annales de Paléontologie 93, 121-147.

BOUVRAIN, G. (1988). Les Tragoportax (Bovidae, Mammalia) des gisements du Miocène supérieur de Ditiko (Macédoine, Grèce). Annales de Paléontologie 74, 4363.

The sample of bovids from As Sahabi is not huge in terms of number of specimens, but it does achieve a wide representation of tribes mainly characteristic of Africa. Cephalophini are absent as at most African localities, but otherwise the only notable absence is Tragelaphini. Pachytragus, its relatives and more readily acceptable Caprini are not totally unknown in the African fossil record, but their absence at a northern locality like As Sahabi does strengthen the impression of an African affinity. Taken together, the bovids give a strong indication of a late Late Miocene or earliest Pliocene date. I thank Noel Boaz for offering me the opportunity to examine these interesting fossils, and members of the As Sahabi field teams for the photographs. The East Libya Neogene Research Project has been supported financially by the U.S. National Science Foundation, including the RHOI program.

GENTRY, A.W. (1980). Fossil Bovidae (Mammalia) from Langebaanweg, South Africa. Annals South African Museum 79, 213-337. GENTRY, A.W. (1997). Fossil ruminants (Mammalia) from the Manonga Valley, Tanzania; In: Neogene Paleontology of the Manonga Valley, Tanzania. (ed T. Harrison). Plenum Press, New York, 107135 GENTRY, A.W. (1999). Fossil pecorans from the Baynunah Formation, Emirate of Abu Dhabi, United Arab Emirates. In: Fossil Vertebrates of Arabia. (eds P.J. Whybrow and A. Hill). Yale University Press, New Haven, 290-316. GENTRY, A.W. (2000) Caprinae and Hippotragini (Bovidae, Mammalia) in the

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Upper Miocene. In: Antelopes, Deer and Relatives: Fossil Record, Behavioral Ecology, Systematics and Conservation. (eds E.S. Vrba and G.B. Schaller). Yale University Press, New Haven, 65-83.

PILGRIM, G.E. (1939). The fossil Bovidae of India. Memoirs of the Geological Survey of India, Palaeontologia Indica NS 26, 1356. PILGRIM, G.E. and SCHAUB, S. (1939). Die schraubenhörnige Antilope des europaïschen Oberpliocaens, und ihre systematische Stellung. Abhandlungen Schweizerische Paläontologische Gesellschaft 62 (3), 1-29.

GERAADS, D. (1989). Vertébrés fossiles du Miocène supérieur du Djebel Krechem el Artsouma (Tunisie Centrale). Comparaisons biostratigraphiques. Geobios 22, 777-801. GERAADS, D. and AMANI, F. (1998). Bovidae (Mammalia) du Pliocène final d’Ahl al Oughlam, Casablanca, Maroc. Paläontologische Zeitschrift 72, 191-205.

THOMAS, H. (1979). Miotragocerus cyrenaicus sp. nov. (Bovidae, Artiodactyla, Mammalia) du Miocène supérieur de Sahabi (Libye) et ses rapports avec les autres Miotragocerus. Geobios 12, 267281.

HAILE-SELASSIE, Y., WOLDEGABRIEL, G., WHITE, T.D., BERNOR, R.L., DEGUSTA, D., RENNE, P.R., HART, W.K., VRBA, E., STANLEY, A. and HOWELL, F.C. (2004). Mio-Pliocene mammals from the Middle Awash, Ethiopia. Geobios 37, 536-552. HARRIS, J.M. (2003). Bovidae from the Lothagam succession. In: Lothagam: The Dawn of Humanity in Eastern Africa. (eds M.G. Leakey and J.M. Harris), Columbia University Press, New York, 531-579. LEHMANN, U. and THOMAS, H. (1987). Fossil Bovidae from the Mio-Pliocene of Sahabi, (Libya). In: Neogene Paleontology and Geology of Sahabi (eds N.T. Boaz, A. El-Arnauti, A.W. Gaziry, J. de Heinzelin, and D.D. Boaz). Liss, New York, 323-335. PETROCCHI, C. (1956). I Leptobos di Sahabi. Bollettino della Società Geologica Italiana 75 (1), 206-238.

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Special Issue, No. 5

Review of Fossil Proboscidea from the Early-Middle Miocene Site of Jabal Zaltan, Libya

WILLIAM J. SANDERS

ABSTRACT

Review of the fossil proboscidean sample from the Marada Formation of Jabal Zaltan (â&#x20AC;&#x153;Gebel Zeltenâ&#x20AC;?), Libya, including previously undescribed specimens from the Savage collection, shows that it includes a taxonomically diverse group of elephantoids, including a mammutid (Zygolophodon sp. indet.), choerolophodont (Choerolophodon zaltaniensis), and three species of gomphotheriines (Gomphotherium angustidens libycum, "pygmy" Gomphotherium sp. indet., and cf. Gomphotherium sp. nov.). A primitive species of deinotheriine (Prodeinotherium hobleyi) also occurs at Jabal Zaltan. Except for an incongruously archaic protogomphothere, the proboscidean taxa from Jabal Zaltan are concordant with an early Middle Miocene age for the site, and are more advanced in occlusal development and probably slightly younger than confamilials from Wadi Moghara, Egypt. Assessment of occlusal morphology and results of isotopic analyses indicate that these taxa were all browsers, employing a variety of masticatory strategies for breaking down different plant parts.

William J. Sanders, Museum of Paleontology, The University of Michigan, 1109 Geddes Avenue, Ann Arbor, Michigan 48109-1079 USA, wsanders@umich.edu

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collection is that amassed by Savage's expeditions of 1964, 1967, and 1968 (Savage and White, 1965; Savage, 1967, 1971; Selley, 1968; Savage and Hamilton, 1973). Among the mammalian assemblage is a substantial sample of proboscidean fossils, documenting the occurrence of a varied assortment of deinothere and elephantoid taxa. A deinothere, several gomphotheriine species, and a choerolophodontine have been recognised in this sample, though opinions have differed about the specific identity and affinities of these taxa (Arambourg, 1961b, 1963; Arambourg and Magnier, 1961; Savage, 1967, 1971, 1989; Harris, 1969, 1973, 1978; Savage and Hamilton, 1973; Coppens, et al., 1978; Gaziry, 1987a; Pickford, 2003, 2004), and the sample has never been comprehensively described. Savage's collection was only recently transferred from the University of Bristol to the Natural History Museum, London, where it became more readily available for study. Increased accessibility of the collection provided the impetus for the present comparative morphological and metrical analyses of its more informative undescribed specimens, and for reassessment of prior taxonomic interpretations of the Jabal Zaltan proboscideans. Definitions of terms used in this paper are as follows: accessory conules - enamel covered pillars situated at the anterior and/or posterior faces of loph(id)s, or in

INTRODUCTION The site of Jabal Zaltan, Libya encompasses a massive, 140-km-long northwest-southeast-oriented mesa deeply dissected by wadis which expose numerous fossil localities (Selley, 1966, 1967, 1968; Savage and Hamilton, 1973). Sediments at the site comprising the Marada Formation represent fluviatile, floodplain, tidal flat, and estuarine depositional environments, and have produced a large, diverse fossil mammalian assemblage (Arambourg, 1961a, b, 1963; Arambourg and Magnier, 1961; Magnier, 1962; Savage and White, 1965; Selley, 1966, 1968; Savage, 1967, 1971, 1989; Savage and Hamilton, 1973). Biochronological correlation suggests an early-middle Miocene age for the Marada Formation within the interval of 19-15 ma (Pickford, 1991; Wessels, et al., 2003). Mammalian fossil remains were first recovered at Jabal Zaltan by Magnier, and subsequently Arambourg, in 1961 (Arambourg, 1961a, b, 1963; Arambourg and Magnier, 1961; Magnier, 1962). These finds were supplemented by oil company donations of specimens to the American Museum of Natural History and the British Museum (Natural History), and fossils more recently recovered by a Czechoslovakian expedition in the early 1980s (Gaziry, 1987a) and during a palaeontological survey headed by El-Arnauti and Daams in the late 1990s (Wessels, 2003; this volume). The most extensive Jabal Zaltan

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mega annum (106 years); mm, millimetre or millimetres; P or p, permanent premolar (for example, P3 is the upper third premolar and p3 is the lower third premolar).

transverse valleys, blocking them centrally (Tobien, 1973a) chevroning - the arrangement of half-lophs or half-lophids to occlusally form an anteriorly pointing "V," or chevron (Tobien, 1975) choerodonty - occurrence of accessory tubercles within transverse valleys (Osborn, 1942) crescentoids - enamel crests running from the apices of outer conelets of pretrite halfloph(id)s to the bottom of transverse valleys, and ending near the middle axis of the crown (Tobien, 1975) intermediate molars - DP4/dp4, M1/m1, and M2/m2 mesoconelets - the inner conelet(s) in each half-loph(id) posttrite - refers to the less worn half of each loph(id), which is lingual in lower and buccal in upper molars (Vacek, 1877) pretrite - refers to the more worn half of each loph(id), which is buccal in lower and lingual in upper molars (Vacek, 1877) ptychodonty - plication or folding of enamel borders with grooving of the sides of the molars (Osborn, 1942) zygodont crests - enamel crests running from the apices of the outer conelets of the posttrite half-loph(id)s to the bottom of the transverse valleys, and ending the near the middle axis of the crown (Tobien, 1975).

DEINOTHERIOIDEA Deinotheriidae Prodeinotherium hobleyi No deinothere fossils were reported by Magnier and Arambourg, but Savage's expeditions to Jabal Zaltan subsequently recovered abundant skeletal remains of these animals. Initially attributed to Deinotherium (Savage and White, 1965) and D. cuvierei (Savage, 1967), these remains were later comprehensively described by Harris (1969, 1973) and more properly assigned to the Early-Middle Miocene African deinotheriine species Prodeinotherium hobleyi, based on craniodental size (Figure 1), as well as cranial, molar, and scapular morphology. Larger dimensions and more advanced cusp morphology of cheek teeth than in Early Miocene specimens from East Africa (e.g., Rusinga, Karangu, and Arongo Uyoma, Kenya, ca. 18-17 ma [Andrews, 1911; MacInnes, 1942; Pickford, 1986; Drake et al., 1988]) indicate a younger age for the Jabal Zaltan deinotheres (Harris, 1973, 1978). That there are no additional deinothere specimens in the previously undescribed portion of the Jabal Zaltan collection reflects the meticulous nature of Harris' efforts (1969, 1973). In addition to Prodeinotherium hobleyi, two other deinothere species are recognised

Abbreviations used are: DP or dp, deciduous premolar (for example, DP3 is the upper third premolar and dp3 is the lower third premolar); i, lower incisor; M or m, molar (for example, M1 is the upper first molar and m1 is the lower first molar); ma,

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Figure 1. Bivariate plots of M3 and m3 crown length versus width in deinotheres and barytheres. Comparative dimensions supplementing original measurements are from Bachmann (1875), Weinsheimer (1883), Roger (1886), Andrews (1911), Foster Cooper (1922), Palmer (1924), Ă&#x2030;hik (1930), MacInnes (1942), GrĂ¤f (1957), Sahni and Tripathi (1957), Symeonidis (1970), Harris (1973, 1977, 1983, 1987), Gaziry (1976), Tobien (1988), Tsoukala and Melentis (1994), Huttunen (2000), Sach and Heizmann (2001), Sanders (2003), Sanders, et al. (2004), and Delmer (2005). Symbols: inverted open triangle, C. harrisi; open circle, P. hobleyi; star, P. hobleyi (Jabal Zaltan); open triangle, P. pentapotamiae; cross, D. bozasi; closed diamond, D. giganteum; "X", D. indicum; right facing triangle, B. grave; left facing triangle, B. sp. indet. (Birket Qarun Fm., Fayum, Egypt). (A) M3. (B) m3.

from Africa: the more primitive, Late Oligocene chilgatheriine Chilgatherium harrisi (Sanders, et al., 2004), and the more derived deinotheriine Deinotherium bozasi, which existed from the Late Miocene until the end of the Early Pleistocene (Harris, 1978; Beden, 1985; Behrensmeyer, et al., 1995). Deinotheriines are ubiquitous in Afro-Arabian fossil sites, and are readily identifiable by their brachyodont, lophodont molars with chisel-like wear across the loph (id)s, strongly down-turned mandibular

symphyses and lower tusks (i2s), lack of upper tusks, and low, elongate crania with deep rostral troughs anterior to retracted nasal openings, likely associated with the presence of a trunk (Figure 2; Harris, 1973, 1975, 1978). The Jabal Zaltan deinothere sample includes the only crania known for the species, which are distinguished from those of Deinotherium bozasi by several primitive features, such as narrower and more anteriorly placed external nares, lower

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Figure 2. Cranial and mandibular specimens of Prodeinotherium hobleyi from Jabal Zaltan, Libya. Anterior is to the left in all specimens. (A) Dorsal view, cranium M26665. (B) Right lateral view, cranium M26665 (reversed). (C) Ventral view, cranium M26665. (D) Occlusal view, mandible with right and left p3-m3 6412:10. (E) Right lateral view, mandible 6412:10 (reversed). occipital condyles, a more vertically angled occiput, and a more steeply downturned rostrum (Harris, 1978). Craniodental features of Prodeinotherium hobleyi, including relatively modestly sized lower tusks and probably short proboscis, suggest that it foraged in dense gallery forest habitats (Harris, 1978). It appears that the dentition was bifunctional, with the premolars acting as an anterior crushing battery, and molars engaged in vertical slicing, presumably to masticate soft browse (Harris, 1973, 1975, 1978). Reliance on a diet of strictly C3 plant material is confirmed by stable isotopic analysis of deinotheriine teeth (Cerling, et al., 2005). ELEPHANTOIDEA Mammutidae Zygolophodon sp. indet. A previously undescribed, unnumbered upper molar fragment in the Jabal Zaltan collection is the first record of a mammutid from the site. The specimen preserves only the anterior cingulum and first two lophs, and is very weathered

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Figure 3. Unnumbered upper molar fragment of Zygolophodon sp. from Jabal Zaltan, Libya, in anterior view.

al., 1997; Pickford, 2003, 2007; Pickford and Mein, 2006). It is claimed that a more basal mammutid occurs in the Eragaleit Beds at Lothidok, Kenya (Gutierrez and Rasmussen, 2007), dated to 27.5-24.0 ma (Boschetto, et al., 1992), but this material has not been described. Zygolophodon spp. appear to have been widely distributed throughout Africa during the Early-Middle Miocene, temporally extending from about 18.0-13.0 ma (Errington de la Croix, 1887; Arambourg, 1959; Robinson, 1974; Robinson and Black, 1974; Madden, 1980; Pickford and Tassy, 1980; Pickford, 1981, 1986, 2003, 2005, 2007; Tassy, 1985, 1986; Thomas and Petter, 1986; Pickford and Senut, 2000; Sanders and Miller, 2002), though evidently were much less common than gomphotheriids during the same interval. Although reminiscent of upper molar morphology in Z. aegyptensis from Wadi Moghara, Egypt (Sanders and Miller, 2002), the poor preservation of the Jabal Zaltan specimen makes it impossible to identify it more precisely than to genus.

(Figure 3). Nonetheless, it exhibits typical mammutid morphology: broad, deeply incised V-shaped median sulci dividing half-lophs (zygolophodonty); mesoconelets much lower than main conelets; anteroposteriorly extensive transverse valley spacing between lophs; zygodont crests on the posttrite half-lophs and anterior and posterior crescentoids on the pretrite halflophs; and antero-posterior compression of loph apices (Tassy, 1985; Tobien, 1975, 1996). The development of crescentoids exceeds that of the archaic mammutid Eozygodon morotoensis, but matches the condition in molars of Zygolophodon species. Molars with this morphology have been described as â&#x20AC;&#x153;tapiroid,â&#x20AC;? and are thought to have been adapted for vertical shearing of leafy vegetation (Tobien, 1996). The earliest unquestionable occurrences of mammutids are those of Eozygodon morotoensis, at Early Miocene sites in eastern and southern Africa, from ca. 23.019.0 ma (Pickford and Tassy, 1980; Tassy and Pickford, 1983; Tassy, 1986; Gebo, et

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the size range for molars of G. angustidens (Figure 4). As shown by m2 specimen P2 and m3 specimen P102 (Figure 5A, B), lophids are configured with tiny mesoconelets transversely adjacent to one another, with their larger outer, main conelets set slightly posterior to them, and are accompanied by pretrite anterior and posterior accessory conules. With wear, these formed trefoil enamel figures. The offset of mesoconelets and outer conelets superficially resembles choerolophodont chevroning, and complicates identification of molars of this gomphotheriine. This type of occlusal morphology has been associated with grinding-shearing mastication of browse (Maglio, 1972). In addition, a largely undescribed agegrade series of jaws with Gomphotherium-type molars from Jabal Zaltan and nearby (see Hormann, 1963) indicates a connection between the Wadi Moghara and Jabal Zaltan samples, and clarifies the mandibular morphology of G. angustidens libycum. From youngest to oldest, the series is comprised of specimens L113, a right dentary with m1 forming in the crypt, and dp3-dp4 (Figure 5C); P4, a left dentary fragment with the alveolus for dp4 above the crypt for p4, roots of m1, and m2 in the crypt; an unnumbered right dentary with dp4 (not m1 as reported by Hormann, 1963), p4 in crypt, and alveoli for p3 and m1; P2, a left dentary with roots of m1, m2 in the crypt, and apparently the remnant of an alveolus for left i2 (Figure 5D); L32, a mandible with alveoli for p4, m1, and m2 just

GOMPHOTHERIIDAE Gomphotheriinae Gomphotherium angustidens libycum Gomphotherium angustidens libycum, the most common elephantoid at Jabal Zaltan, belongs in this subspecies. Ironically, it is also the least welldescribed proboscidean taxon from the site. While generally resembling EarlyLate Miocene European Gomphotherium angustidens (Tassy, 1985; Gรถhlich, 1998), it is placed here in G. angustidens libycum to denote the particular closeness of its molar occlusal morphology and mandibular symphyseal structure to specimens from Early Miocene Wadi Moghara, Egypt placed in that subspecies (Sanders and Miller, 2002). It is not clear if Magnier and Arambourg recovered this taxon from Jabal Zaltan, or only a smaller species of gomphothere (see below; Arambourg, 1961b, 1963; Arambourg and Magnier, 1961), but it was reported after Savage commenced work at the site, under either the now outdated nomen "Mastodon angustidens" or G. angustidens (e.g., Savage, 1967, 1971; Savage and Hamilton, 1973; Coppens, et al., 1978). The Jabal Zaltan sample of G. angustidens libycum has trilophodont intermediate molars, third molars with four loph(id)s, and retained lower incisors and permanent premolars. The molars are brachyodont, with heavy, bulbous outer conelets, and exhibit little or no cementum. Their dimensions fall within

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Figure 4. Bivariate plots of M3 and m3 crown length versus width in palaeomastodonts and Afro-Arabian and selected Eurasian gomphotheriids. Comparative dimensions supplementing original measurements are from Andrews (1906), Fourtau (1918), Foster Cooper (1922), Matsumoto (1924), Lehmann (1950), Bergounioux and Crouzel (1959), Arambourg (1961), Hamilton (1973), Gaziry (1976, 1987a), Tassy (1983b, 1985, 1986), Gentry (1987), Roger et al. (1994), Gรถhlich (1998), Sanders and Miller (2002), Pickford (2003, 2004, 2005), Sanders (2003), and Sanders et al. (2004). Symbols: open diamond, P. wintoni, female; large open diamond, P. wintoni, male; inverted open triangle, Pal. sp nov. A; open triangle, Pal. sp. nov. B; open circle, P. serridens, female; large open circle, P. serridens, male; open square, P. major; plus sign, Fayum palaeomastodont gen et sp indet; open cross, Hemimastodon; star, cf. Gomphotherium sp. nov., Jabal Zaltan; closed square, Eritreum; left facing closed triangle, G. cooperi; closed triangle, G. sylvaticum; M, Gomphotherium sp.; closed circle, G. angustidens (Europe); cross, G. angustidens libycum; right facing closed triangle, G. browni; B, G. pygmaeus, Bosluis Pan; G, pygmy gomphothere, Ghaba; K, G. pygmaeus, Kabylie; N, G. pygmaeus, Ngenyin; S, pygmy gomphothere, Siwa; Z, pygmy gomphothere, Jabal Zaltan; closed diamond, Tetralophodon sp. nov.; "X", Tetralophodon sp. nov., Chorora. (A) M3. (B) m3.

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Figure 5. Gomphotheriid mandibular and molar specimens from Jabal Zaltan, Libya. Anterior is to the left in all specimens. Abbreviations: a.c., anterior accessory central conule; i.a., incisor alveolus; m.c., mesoconelet; m.f., mandibular foramen; p.c., posterior accessory central conule; x, anterior or posterior cingulum(id). A, B to same scale. C-E to same scale. F-H to same scale. (A) Occlusal view, m2 specimen P2, Gomphotherium angustidens libycum. (B) Occlusal view, m3 specimen P102, G. angustidens libycum. (C) Right lateral view, dentary L113 (reversed), G. angustidens libycum. (D) Left lateral view, dentary P2, G. angustidens libycum. (E) Dorsal view, mandible L32, G. angustidens libycum. Note broad symphyseal â&#x20AC;&#x153;gutter.â&#x20AC;? (F) Occlusal view, M3 specimen M21866, cf. Gomphotherium sp. nov. (G) Occlusal view, partial M3 specimen with no accession number, Choerolophodon zaltaniensis. Note posterior position of the pretrite main conelet relative to its mesoconelet, and the offset of paired pre- and posttrite halfloph main conelets. (H) Occlusal view, m3 specimen L76, Choerolophodon zaltaniensis. Note the chevroning of the pretrite and posttrite half-lophids, indicated by arrows. 225

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anterior accessory conules; very lowcrowned loph(id)s; and no choerodonty or ptychodonty. Third molars of this species have four loph(id)s. Specimen Z13, an m3, is 115 mm in length and 65 mm wide (Gaziry, 1987a); M3 specimen 1961-5-12 is 110 mm in length and 57 mm wide (Arambourg, 1961b). These are similar in size to "pygmy" gomphothere molars from Siwa, Egypt and Ghaba, Oman (Hamilton, 1973; Roger, et al., 1994), which are at the lower extreme of the range for Gomphotherium spp. (Figure 4). Specimen W3, a left ?m3 in the undescribed portion of the Savage sample, may also belong in this small species of Gomphotherium. It is +84.5 mm in length, +50.2 mm wide, and preserves three lophids and a diminutive postcingulid. Each half-loph(id) is composed of a small mesoconelet and larger main conelet, aligned straight transversely and accompanied by pretrite posterior accessory conules and barely discernable anterior conules. The crown exhibits no cementum or apical crowding of conelets. A fragmentary mandible (specimen L32) was also placed in this taxon by Pickford (2003), based on erroneous identification of a posterior molar with an estimated length of 111 mm as m3. Rather, this molar, with three lophids and a prominent postcingulid composed of two large conelets, is an m2 preceded by alveoli for p4 and m1, and in size and morphology belongs in Gomphotherium angustidens libycum (see above). The nomenclature of the taxon into which the Jabal Zaltan small gomphothere specimens were originally placed has varied over time along with changes in gomphothere taxonomy, from Trilophodon

erupting, as well as alveoli for right and left i2 (Figure 5E); and H2, a right dentary with m2 and partial m3 (contra Pickford, 2003). These jaws have wide symphyseal gutters, symphyseal angulation that increased substantially downward with age, large arterial foramina that communicate medially from the mandibular canal to just posterior to the i2 alveoli, and three mandibular foramina: a large opening below the anteriormost cheek tooth, a smaller foramen lateral to the symphysis, and a capacious ("torpedo-tube") opening anterior and ventral to that, marking the anteriormost extent of the mandibular canal. Tassy (1985) speculated that a dentary from Wadi Moghara with similar morphology might have choerolophodontine affinities, but the Jabal Zaltan specimens show that broad guttering and downward angulation of the symphysis are also present in some forms of Gomphotherium. "Pygmy" Gomphotherium sp. indet. Several molars from Jabal Zaltan described by Arambourg (1961b) and Gaziry (1987a) belong in a separate, small species of Gomphotherium, termed here "pygmy" Gomphotherium sp. indet. Contra Coppens, et al. (1978), generic identity seems clear from features such as transversely straight alignment of pre- and posttrite half-loph(id) conelets; presence of pretrite anterior and posterior accessory conules that contribute to trefoil enamel wear figures; lack of posttrite accessory conules; and trilophodont intermediate molars. Molars of this species also have bulbous main conelets that dominant diminutive accompanying mesoconelets; abundant cementum in transverse valleys and coating loph(id)s; larger posterior than

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pygmaeus (Arambourg, 1961b) to Mastodon pygmaeus (Arambourg, 1963, Savage, 1971; Savage and Hamilton, 1973) to Gomphotherium pygmaeum (sic, Savage, 1989). Although Roger, et al. (1994) considered Gomphotherium pygmaeus a nomen dubium because of perceived inadequacy of the type, reconsideration of the peculiar combination of features in the type m3 from Kabylie, Algeria (DepĂŠret, 1897; Bergounioux and Crouzel, 1959) and addition of new fossils from Ngenyin, Kenya (Pickford, 2004) and Bosluis Pan, South Africa (Pickford, 2005) to the species confirm its validity (Sanders, et al., in prep.). Because of thick molar cementum and loph(id) chevroning, it has been suggested that this species is a choerolophodont (Tobien, 1973b; Pickford, 2004). It is evident, however, that "pygmaeus" should be maintained in Gomphotherium, as its molar chevroning is an artefact of occlusal crowding rather than transverse offset of half-loph(id)s and anterior advancement of pretrite mesoconelets, relative to their neighboring posttrite mesoconelets. Also, development of thick cementum is wildly homoplasic among proboscideans. In any case, greater occlusal and apical crowding of molar conelets, loph(id) chevroning, and thicker of investiment of cementum in G. pygmaeus than in "pygmy" gomphotheres from Jabal Zaltan (and Siwa [Hamilton, 1973] and Ghaba [Roger, et al., 1994]) indicate that they belong in different species. Although Gaziry (1987a) placed the molars of the small gomphotheres from Jabal Zaltan in G. angustidens pasalarensis, their size supports attribution to a separate species.

cf. Gomphotherium sp. nov. An enigmatic M3, M21866, derives from a very diminutive gomphotheriine. It was donated by the Oasis Oil Company to the British Museum (Natural History) in 1962, and its field coordinates place its provenance close to the southwest face of the escarpment. The specimen is subtriangulate in occlusal outline, has only three lophs and a prominent postcingulum, bulbous main conelets that dominate much smaller mesoconelets, weakly developed pretrite anterior and posterior accessory conules, faint traces of cementum, and is extremely brachyodont (Figure 5F). Morphologically, it is reminiscent of an m3 from the Late Oligocene site of Chilga, Ethiopia assigned to "cf. Gomphotherium sp. nov." (Sanders, et al., 2004), and is incongruously primitive in comparison with all other Jabal Zaltan elephantoids (Pickford, 2003). The only elephantoid third molars smaller than M21866 are those of Late Oligocene Eritreum melakeghebrekristosi from Dogali, Eritrea (Shoshani, et al., 2006). Comparison with a large sample of elephantiform proboscideans shows that M21866 is within the upper range of molar size for palaeomastodonts, and even more diminutive (length=96 mm; width=55 mm) than molars of Gomphotherium pygmaeus and other Early-Mid Miocene "pygmy" gomphotheres (Figure 4; DepĂŠret, 1897; Bergounioux and Crouzel, 1959; Hamilton, 1973; Roger, et al., 1994; Pickford, 2004). Specimen M21866 also differs from these gomphotheres by having three, rather than four, lophs. Gradistically, in size and structure, M21866 is either a protogomphothere, or belongs in the archaic

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in C. zaltaniensis, including an anteriorly broken left ?M3 with no accession number (Figure 5G), dentary fragment L76 with m2-3 (Figure 5H), and P131, an m3. These corroborate the morphological details of the specimens described by Gaziry (1987a), and show that choerolophodonts were more widely represented across the localities of Jabal Zaltan. Conversely, an m3 (specimen X7) assigned to C. zaltaniensis (Pickford, 2003) belongs instead in G. angustidens libycum. It does not exhibit chevroning, and its mesoconelets and half-lophids are transversely arranged in straight lines, accompanied by pretrite anterior and posterior accessory conules. African choerolophodonts other than C. zaltaniensis include the archaic EarlyMiddle Miocene Afrochoerodon kisumuensis (MacInnes, 1942; Tassy, 1977, 1986; Pickford, 2001, 2003, 2005; Behrensmeyer, et al., 2002; Sanders and Miller, 2002), and more derived C. ngorora (Maglio, 1974; Tassy, 1977, 1986; Pickford, 1981; Nakaya, 1993; Tsujikawa, 2005; Nakatsukasa, 2007), which is divisible into Middle Miocene "primitive" and early Late Miocene "advanced" morphs (Tassy, 1986), or possibly into separate species (Pickford, 2004). Although Pickford (2001) transferred C. zaltaniensis to Afrochoerodon when he named the genus, morphologically it is closer in size (Figure 6) to the primitive morph of C. ngorora, with greater development of choerodonty and ptychodonty, thicker investment of cementum, stronger chevroning of loph(id)s, and invariant presence of four lophs in M3, and he later returned "zaltaniensis" to Choerolophodon (Pickford, 2004).

"Gomphotherium annectens group" (Tassy, 1985, 1986, 1994, 1996). Its overall morphology suggests that its small size reflects a primitive aspect rather than a case of dwarfing. Choerolophodontinae Choerolophodon zaltaniensis Gaziry (1987a) first identified choerolophodonts from Jabal Zaltan, all collected at locality Z, and named Choerolophodon zaltaniensis to accommodate them. Documented by only a handful of specimens, nonetheless the choerolophodont affinity of this species is clear from the chevroning of posterior lophs or lophids, anterior displacement of pretrite mesoconelets, and oblique alignment of pretrite half-loph(id)s relative to the long axis of the crown. The interruption of transverse valleys by the offset of halflophs or lophids suggests enhancement of the horizontal grinding component of mastication. Isotopic analysis of African choerolophodonts shows that they were dedicated browsers (Cerling et al., 1999). Intermediate molars are trilophodont and third molars have four loph(id)s. In M3, small pretrite posterior accessory conules are associated with lophs 1-3. The cranium is unknown for this species. A juvenile dentary has a broad symphyseal gutter, but is too incomplete anteriorly to gauge symphyseal angulation or presence or absence of lower tusks (Gaziry, 1987a). Lower tusks are absent in all more completely known choerolophodont species (Tassy, 1985, 1986). Several molars from the undescribed portion of Savage's collection also belong

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Figure 6. Bivariate plots of M3 and m3 crown length versus width in African and selected Eurasian amebelodonts and choerolophodonts. Comparative dimensions supplementing original measurements are from Foster Cooper (1922), Tiercelin, et al. (1979), Tassy (1983a, b, 1985, 1986), Gaziry (1976, 1987a, b), Suwa, et al. (1991), Pickford (2001, 2003), Sanders and Miller (2002), and Sanders (2003). Symbols: open circle, A. kisumuensis; open circle with dot, "Ch." palaeindicus; star, C. zaltaniensis; open square, C. ngorora; open cross, cf. Choerolophodon (S. Asia); inverted open triangle, C. anatolicus; open triangle, C. pentelici; open diamond, C. corrugatus; B, Burji gomphotheriid; "X", Progomphotherium maraisi; inverted closed triangle, cf. Archaeobelodon; closed triangle, A. filholi; closed diamond, P. macinnesi; closed square, P. chinjiensis; closed circle, A. coppensi; closed right pointing triangle, A. cyrenaicus. (A) M3. (B) m3.

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mammalian evolution in North Africa, and because the Marada Formation cannot be as precisely dated as penecontemporaneous sites from eastern Africa. The mammals from Jabal Zaltan were initially estimated to be of Burdigalian or Orleanian (Early Miocene) age, closely comparable temporally with the fossil mammals from Wadi Moghara, Egypt, based in part on the gomphotheriine and deinothere occurrences (Arambourg, 1961, 1963; Arambourg and Magnier, 1961; Magnier, 1962; Savage and White, 1965; Savage, 1971, 1989; Savage and Hamilton, 1973). More recently, biochronological correlation of large mammals indicated a latest Early Miocene age of 18-17 ma for Wadi Moghara, and assigned a slightly younger, early Middle Miocene date of 17-16 ma to Jabal Zaltan (Pickford, 1991; Miller and Simons, 1996; Miller, 1999). Study of the micromammals from Jabal Zaltan suggested a more complex succession of three assemblages within the interval 19-15 ma (Wessels, et al., 2003; this volume). The proboscidean taxa from Jabal Zaltan can be cautiously interpreted as supporting the presence of multiple fossilbearing horizons in the Marada Formation. The occurrence of a very primitive gomphotheriine, cf. Gomphotherium sp. nov., is indicative of either an Early Miocene or even Late Oligocene age. The remaining proboscideans from the site appear to be slightly younger than confamilials from Wadi Moghara and to have derived from early Middle Miocene deposits. Gomphotherium angustidens libycum is more advanced at Jabal Zaltan than at Wadi Moghara, with four loph(id)s in all third molars. Choerolophodon zaltaniensis is more derived in occlusal

DISCUSSION Taxonomy and Paleoecology Review of the proboscidean sample from Jabal Zaltan, including previously undescribed specimens from Savageâ&#x20AC;&#x2122;s collection, confirms the presence of the deinothere Prodeinotherium hobleyi, and shows that the elephantoids from the site are more taxonomically diverse than previously reported. The elephantoids include the first mammutid documented from Jabal Zaltan, assignable to Zygolophodon sp. indet., the more common gomphotheriine Gomphotherium angustidens libycum, a smaller, unnamed â&#x20AC;&#x153;pygmyâ&#x20AC;? species of Gomphotherium, and the choerolophodontine Choerolophodon zaltaniensis. In addition, a protogomphothere or a very primitive stage of Gomphotherium is also documented. Occlusal morphology and dental isotopic analysis of these taxa indicate that they were all likely to have been browsers. However, their masticatory mechanics and dietary specializations probably varied widely, from an emphasis on vertical slicing associated with folivory in P. hobleyi to powerful horizontal grinding, possibly for breaking down more pulpy browse (fruits, pith), in C. zaltaniensis, with the gomphotheriines occupying intermediate generalist niches. Age Establishing the antiquity of the faunal assemblage from Jabal Zaltan is critically important, since along with Wadi Moghara, Egypt it comprises the most representative perspective of early Neogene 230

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Museums, Dar es Salaam), Ezra Musiime (Ugandan Museum, Kampala), Mohammed el-Bedawi (Cairo Geological Museum, Cairo), and particularly Jerry Hooker (The Natural History Museum, London). I am especially grateful to Bonnie Miljour (University of Michigan, Ann Arbor) for composing the figures. Peter Robinson (University of Colorado, Boulder) provided invaluable bibliographic assistance. John Harris (George C. Page Museum, Los Angeles) kindly gave permission for the use of the deinothere photographs in Figure 2. This research was generously supported by several Turner Grants from the Department of Geological Sciences, University of Michigan, and through grants to Terry Harrison (New York University, New York), John Kappelman (University of Texas, Austin), and Laura MacLatchy (University of Michigan, Ann Arbor).

morphology than the archaic choerolophodont Afrochoerodon kisumuensis from Moghara (Sanders and Miller, 2002), but is more primitive in occlusal complexity than ca. 14-11 ma C. ngorora from Ft. Ternan and Mbs. A-D in the Ngorora Formation, Tugen Hills, Kenya (Tassy, 1986) and Late Miocene C. pentelici from Turkey (contra Gaziry, 1987a). The size and morphology of the deinothere molars suggest an age younger than Early Miocene East African sites (Harris, 1973). "Pygmy" gomphotheres and Zygolophodon spp. are broadly dated to the Early-Middle Miocene in Africa, and cannot refine age estimates for Jabal Zaltan (Sanders, et al., in prep.). It is possible that the mammutid from Jabal Zaltan is conspecific with that from Moghara, but more complete molars are required to confirm this. Contrary to published accounts (Coppens, et al., 1978; Pickford, 2003), there is no evidence of either "pygmy" gomphotheres or C. zaltaniensis at Wadi Moghara.

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TSUJIKAWA, H. (2005). The updated late Miocene large mammal fauna from Samburu Hills, northern Kenya. African Study Monographs Supplement 32, 1-50. VACEK, M. (1877). Ueber Osterreichische Mastodonten und ihre Beziehungen zu den Mastoden-Arten Europas. Abhandlungen der Kaiserlich-Koninglichen Geologischen Reichenstalt 7, 1-45. WEINSHEIMER, O. (1883). Ueber Dinotherium giganteum Kaup. Palaeontologische Abhandlungen 1, 205282. WESSELS, W., FEJFAR, O., PELﾃ・ZCAMPOMANES, P., VAN DER MEULEN, A., and DE BRUIJN, H. (2003). Miocene small mammals from Jebel Zelten, Libya. Coloquios de Paleontologia Vol. Ext. 1, 699-715.

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Review of Fossil Proboscidea from the Late MioceneEarly Pliocene Site of As Sahabi, Libya WILLIAM J. SANDERS

ABSTRACT Fossil proboscideans from the Late Miocene-Early Pliocene site of As Sahabi, Libya are part of the most comprehensive mammalian fauna from this North African time interval. They are diverse and include an anancine gomphothere, an archaic stegotetrabelodontine elephant, a slightly more advanced, indeterminate second species of elephant (formerly recognised as a stegodont), and (unexpectedly) an amebelodont with shoveled lower tusks. The anancine belongs in the species Anancus petrocchii, and is moderately derived, with pentalophodont intermediate molars, third molars with six loph(id)s, and occurrence of pre- and posttrite accessory conules throughout molar crowns. This species has only been documented at As Sahabi. The stegotetrabelodontine is a very large elephant, and has been placed in Stegotetrabelodon syrticus. Its most salient feature is its very elongate lower incisors. Its occlusal morphology is very primitive, with strong accessory conules throughout molar crowns that are brachyodont and formed of few plates. The amebelodont has derived, flattened lower tusks that were evidently used to scoop up vegetation. The shape of its tusks suggests that it belongs in its own species, Amebelodon cyrenaicus, which also only occurs at As Sahabi. This is the youngest occurrence of the genus Amebelodon. The co-occurrence of these taxa indicates that contrasting ecosystems were present at As Sahabi, including open country areas with graze as well as more forested, possibly wetter conditions. It also suggests that either As Sahabi contains several successive faunas from the Late Miocene-Early Pliocene, or that the proboscidean sample is composed of a sympatric mix of Early Pliocene taxa and relictual survivors from the Late Miocene.

William J. Sanders, Museum of Paleontology, The University of Michigan, 1109 Geddes Avenue, Ann Arbor, Michigan 48109-1079 USA, wsanders@umich.edu

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the inclusiveness and taxonomy of each of these species would benefit from further analyses, and that the proboscidean fauna from the site may be more diverse than previously realized. Despite the report of Petrocchi (1941), there is no contemporary evidence for deinotheres at As Sahabi.

INTRODUCTION Fossiliferous exposures of the Sahabi Formation at the site of As Sahabi, northern Libya, have yielded a large collection of Late Miocene-Early Pliocene mammals. This assemblage is notable for being the most comprehensive record of mammals from this time period in North Africa, for its taxonomic diversity, including terrestrial and marine species, and for its far-reaching biogeographic links to sub-Saharan Africa and Eurasia (Bernor and Pavlakis, 1987; Boaz, 1987; Bernor and Scott, 2003). In addition, a wide range of depositional environments are represented by the sediments of the Sahabi Formation, such as shallow marine waters, lagoons, deltas, estuaries, and tide channels (de Heinzelin and El-Arnauti, 1987). The As Sahabi area was first prospected by Italian teams led by Desio, and subsequently Petrocchi in the 1930s, and more recently by the International Sahabi Research Project in the 1970s and early 1980s (Boaz et al., 1982; Boaz, 1987; de Heinzelin and El-Arnauti, 1987; Rook, this volume; Boaz et al., this volume). Proboscidean remains are relatively abundant in the mammalian assemblage from As Sahabi, and include an unusual mix of amebelodonts, anancine gomphotheres, and archaic stegotetrabelodontine elephants (Petrocchi, 1941, 1943, 1954; Gaziry, 1982, 1987). Each of the proboscidean taxa from As Sahabi is unique at the species level. Together, they generally support interpretations that the site is boundary MioPliocene in age, ca. 5.2 ma (e.g., Bernor and Scott, 2003), and provide evidence for broad biogeographic connections and a mosaic of habitats. The present review indicates that

Definitions The following terms are used in descriptions. Accessory conules - enamel covered pillars situated at the anterior and/or posterior faces of loph(id)s, or in transverse valleys, blocking them centrally (Tobien, 1973) Intermediate molars - DP4/dp4, M1/m1, and M2/m2 Mesoconelets - the inner conelet(s) in each half-loph(id) Posttrite - refers to the less worn half of each loph(id), which is lingual in lower and buccal in upper molars (Vacek, 1877) Pretrite - refers to the more worn half of each loph(id), which is buccal in lower and lingual in upper molars (Vacek, 1877). Abbreviations The following abbreviations are used. DP or dp - deciduous premolar (for example, DP3 is the upper third premolar and dp3 is the lower third premolar) H - height i - lower incisor L, length M or m, molar (for example, M1 is the upper first molar and m1 is the lower first molar) ma - mega annum (106 years) mm - millimeter(s) P or p - permanent premolar (for example, P3 is the upper third premolar and p3 is the lower third premolar) W - width x - anterior or posterior cingulum(id)

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surfaces worn from use, suggesting a shoveling or scooping function. Amebelodontines are known as "shoveltuskers" because of the great broadening and dorsoventral compression of their i2s, particularly in Protanancus, Amebelodon and most notably in Torynobelodon and Platybelodon (Osborn and Granger, 1931, 1932; Osborn, 1936; Lambert, 1990, 1992). In more primitive members of the subfamily, however, such as Archaeobelodon, lower tusks are far less flattened (Tassy, 1984, 1986). The archaic gomphotheres Progomphotherium maraisi and Afromastodon coppensi exhibit craniodental features consistent with placement in Amebelodontinae (Sanders, et al., in press),

Gomphotheriidae Amebelodontinae Amebelodon cyrenaicus The only reliable record of this genus in Africa is from As Sahabi, based primarily on a number of flattened lower tusk (i2) fragments with internal dentinal tubules and rods (Gaziry, 1982, 1987). These were all collected between 1978-1981 by the International Sahabi Research Project. The most complete of these i2s, 481P34A, has dimensions of L=+420 mm; W=127 mm; H=44 mm. Its cross-section is shown in Figure 1D. These tusks have dorsal and ventral longitudinal sulci, and ventral

Figure 1. Selected African amebelodont i2 cross-sections, medial side to the left, all to same scale. (A) KNM-MI 7532, Archaeobelodon filholi. (B) M15532 (KBA 109), Protanancus macinnesi. (C) Semliki no 531A, Protanancus macinnesi. (D) As Sahabi 481P34A, Amebelodon cyrenaicus (reversed). (E) MCZ 38-64K, Platybelodon sp.

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and have i2s that are even more ovoid in cross-section (Pickford, 2003). The compression index (CI=H x 100/W) of A. cyrenaicus i2 is 35, not as compressed as i2s of Platybelodon from the early Miocene site of Loperot, Kenya (CI=19; Maglio, 1969) and Asian and North American Platybelodon and Torynobelodon (Osborn and Granger, 1931, 1932; Osborn, 1936; Guan, 1996), but flatter in proportion than lower tusks of Afromastodon coppensi (CI=68-84), African Archaeobelodon (CI=48-52), and most Protanancus macinnesi (CI=35-50). The degree of flattening of the As Sahabi i2s is consistent with taxonomic assignment to Amebelodon, and their cross-sectional shape supports Gaziry's (1987) recognition of a new species. A number of molars have also been attributed to this species, including a t r i l o p h o d o n t m1 ( L = 1 5 7 m m ) , tetralophodont m2 (L=170 mm), and third molars with six lophids (L=211 mm; +214 mm) (Gaziry, 1982, 1987). Pretrite halflophids have large posterior and diminutive anterior central accessory conules, forming trefoil enamel shapes in wear. Posttrite and pretrite half-lophids are transversely aligned, there are no posttrite accessory conules, and cementum may fill transverse valleys (Gaziry, 1987). There is no certainty that these teeth belong to the same taxon as the flattened lower tusks or each other. For example, the association of an m1 with three lophids with a tetralophodont m2 is highly unusual for a gomphothere, and the alignment of half-lophids and absence of posttrite accessory conules are not typical for more advanced amebelodontines such as Amebelodon.

Anancinae Anancus petrocchii Anancine gomphothere fossils from As Sahabi were first reported by Petrocchi (1941, 1943, 1954), who placed teeth and jaws comprising the sample into Pentalophodon sivalensis. Coppens (1965) later recognized the anancine affinity of these specimens and placed them in a new species, Anancus (Pentalophodon) petrocchii, which to date has only been documented at As Sahabi. Anancine gomphotheres are marked by brevirostrine mandibles lacking lower tusks (including A. petrocchii specimen no. 1 from As Sahabi [Petrocchi, 1954: 52-56]); short, wide crania with domed, elevated vaults and very raised bases (African specimens); straight upper tusks without enamel; and especially by anancoidy of preand posttrite half-loph(id)s. In upper molars, pretrite half-lophs are anterior to their paired posttrite half-lophs, while the reverse occurs in lower molars (Coppens. et al., 1978; Tassy, 1985, 1986; Kalb and Mebrate, 1993). In Africa, a number of species separated regionally have been recognised, including Anancus kenyensis (Central and East Africa), A. osiris and A. petrocchii (North Africa), and A. capensis (South Africa). As diagnosed, Anancus petrocchii is distinguished from other African anancines by its combination of pentalophodont intermediate molars; third molars with six lophids, simplicity of occlusal organization, and weak anancoidy (Figure 2); massiveness of its pyramidal lophids; and large size and relative narrowness of its third molars (Figure 3). Illustration of A. petrocchii m3 specimen As Sahabi no. 8 by Petrocchi (1954: Fig. 20B) shows the occurrence of large central

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Figure 2. Comparative African anancine gomphothere molar morphology. Abbreviations: ac, pretrite anterior accessory central conule; pc, pretrite posterior accessory central conule; poa, posttrite anterior accessory central conule; pop, posttrite posterior accessory central conule; x, anterior or posterior cingulum(id); t. nf., “tubercle de nÈoformation” (Arambourg, 1945, 1970); 1, 2, 3, . . . ., first, second, third, . . . loph(id). Anterior is to the left in all specimens. (A) Left m3, KNM-LU 57, Anancus kenyensis, primitive morph; (B) Left m3, EP 197/05, A. kenyensis, advanced morph; (C) Left M3, SAMPQ-L 41692, A. capensis (type), occlusal view (arrows denote relative position of preand posttrite half-lophs; in upper molars, pretrite half-lophs are offset anterior to postrrite half-lophs); (D) Left M3, SAM-PQ-L 41692, A. capensis (type), lingual view; (E) Right m3, As Sahabi molar no. 8, A. petrocchii (Petrocchi, 1954, fig. 20B) (F) Right m3, 1956-4: A1, A. osiris. (G) Right M3, unnumbered, A. petrocchii, As Sahabi (reversed), occlusal view. (H) Left partial m2 and m3, unnumbered, A. petrocchii, As Sahabi, occlusal view.

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Figure 3. Bivariate plot of m3 crown length versus width in African and selected Eurasian anancine gomphotheres. Comparative dimensions supplementing original measurements are from Arambourg (1945, 1970), Petrocchi (1954), Tassy (1986, 1995), Tobien, et al. (1988), Boeuf (1992), and Metz-Muller (1995). Symbols: open inverse triangle, A. kenyensis, primitive morph; open triangle, A. kenyensis, advanced morph; open square, A. capensis; open diamond, A. osiris; open circle, A. petrocchii; closed circle, A. arvernensis; closed triangle, A. sinensis conules (or "tubercles de nĂŠoformation" [Arambourg, 1945, 1970], which appear to be displaced posttrite mesoconelets, a feature shared with A. osiris [Figure 2E-H], and perhaps diagnostic of a North African clade) associated with each lophid, but otherwise no pre- or posttrite accessory conules. By comparison, late Pliocene A. osiris has tetralophodont intermediate molars, but more pronounced anancoidy and higher molar crowns (Arambourg, 1945, 1970; Coppens, 1965; Coppens et al., 1978; Tassy, 1986; Geraads and Metz-Muller, 1999; Sanders et

al., in press), and latest Miocene-earliest Pliocene A. capensis has tetralophodont intermediate molars with greater folding of enamel, an incipient seventh lophid in m3, more pronounced anancoidy, and more complex distribution of accessory conules throughout molar crowns (Figure 2C-D; Sanders, 2006, 2007). Anancus kenyensis, first named by MacInnes (1942) and properly placed in Anancus by Arambourg (1947), was partitioned into four time successive stages by Mebrate and Kalb (1985), into Late MioceneEarly Pliocene primitive (Figure 2A) and early-mid Pliocene advanced (Figure 2B) 246

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and prominent posterior accessory conules, often throughout the extent of the crown, and by retention of very elongate, projecting lower tusks (L>2000 mm in As Sahabi Stegotetrabelodon), long mandibular symphyses, and permanent premolars (Maglio, 1973; Coppens et al., 1978) (Figure 4) These archaic elephants first appeared in Africa and, except for a couple of Arabian and Mediterranean occurrences (Andrews, 1999; Tassy, 1999; Ferretti et al., 2003), are primarily African taxa. Stegotetrabelodonts from East Africa, including Western Rift localities, are temporally well constrained within a Late Miocene-Early Pliocene interval, between at least 7.4-4.2 ma, and have been placed in Stegotetrabelodon orbus (Maglio, 1970, 1973; Hill et al., 1985, 1986; Tassy, 1986; Pickford et al., 1993; Tassy, 1995, 2003; Harrison and Baker, 1997; Sanders, 1997; Kingston et al., 2002; McDougall and Feibel, 2003; Sanders et al., in press). Stegotetrabelodonts documented by Petrocchi (1941, 1943, 1954) and Gaziry (1982, 1987) and placed in Stegotetrabelodon syrticus (Petrocchi, 1941) are likely to derive from within the same time span. Much of the morphology of this species is primitive. For example, lamellar frequency is low (m3=2.7; M3=3.0), plate formulae are low (dp4=x4x; m1=x4x; m3=x7x; P4=x2x; M2=x5-x5x; M3=x6x), molar plates are pyramidal in cross-section, usually have only four-six conelets, and are widely separated by Vshaped transverse valleys. However, the preserved morphology of the cranium suggests an elevated, antero-posteriorly compressed elephantine-like configuration, and with moderate wear plates occlusally formed complete transverse enamel loops (Figure 4). This configuration of cranio-

morphs by Tassy (1986), and into separate species (Sanders et al., in press), to accommodate substantial directional increase in occlusal complexity, crown size, and loph(id) number. It is unfortunate that Tassy (1986) chose to name the advanced stages of the species "A. kenyensis 'petrocchii-morph'," since this form differs from As Sahabi A. petrocchii described by Petrocchi (1943, 1954) by its greater enamel folding, more complex distribution of accessory conules throughout molar crowns, and more pronounced anancoidy. The primitive morph of A. kenyensis is more similar to Petrocchi's conception of A. petrocchii, but has tetralophodont intermediate molars. Re-examination of As Sahabi anancine specimens adds to Petrocchi's (1954) depiction of them. The occlusal pattern is more complex than previously described, with small pre- and posttrite accessory conules throughout upper and lower molar crowns (Figure 2G, H), and with coarsely folded enamel in worn specimens. This new assessment of a more advanced molar occlusal pattern in A. petrocchii suggests that the western, upper parts of the Sahabi Formation, where the Italian teams primarily collected in the 1930s (Boaz et al., this volume) are Early Pliocene, rather than Late Miocene, in age. Elephantidae Stegotetrabelodontinae Stegotetrabelodon syrticus Stegotetrabelodonts are the most primitive elephants known, as indicated by the plesimorphic condition of their molars, including strong median longitudinal sulci, few, low-crowned plates formed of a small number of conelets, thick unfolded enamel,

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Figure 4. Aspects of As Sahabi elephant craniodental morphology. Abbreviations: pc, posterior accessory central conule; x, anterior or posterior cingulum(id); 1, 2, 3 . . . , first, second, third, . . . . loph(id). Anterior is to the left in all specimens. (A) Right m3, unnumbered, Stegotetrabelodon syrticus (reversed), occlusal view. (B) Right m3, unnumbered, S. syrticus (reversed), buccal view. (C) Mandible with projecting i2s, unnumbered, S. syrticus, lateral view (tusks project 1615-1685 mm from incisor alveoli). (D) Reconstruction of the skull of S. syrticus, based on Maglio (1973: fig. 7B), lateral view. (E) Left M3, unnumbered, Elephantidae sp. indet. (="Stegodon syrticus" of Petrocchi [1943, 1954]), occlusal view. 248

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dental anatomy has been associated with fore-aft power shearing of teeth for grazing (Maglio, 1972, 1973). Although the As Sahabi elephants have not been sampled, carbon isotope analyses on specimens from East Africa have confirmed that stegotetrabelodonts were preferentially eating grasses and other C4 plants (Cerling et al., 1999, 2003), despite the brachyodont condition of their molars. DISCUSSION Taxonomy and Paleoecology The genus Amebelodon has been divided, with the more advanced subgenus Amebelodon (Konobelodon) distinguished from A. (Amebelodon) by tetralophodonty of intermediate molars, third molars with six loph(id)s, and lower tusks with dentinal tubules and rods (Lambert, 1990). By these apomorphic criteria (Lambert and Shoshani, 1998), the As Sahabi i2s belong in Amebelodon (Konobelodon). If molars attributed to A. cyrenaicus by Gaziry (1987) are associated with these i2s, they are unexpectedly plesiomorphic in occlusal features by comparison, for such a late-occurring amebelodont (Tassy, 1985; Lambert and Shoshani, 1998). At least m3 specimen 200P15A is more reminiscent of Tetralophodon molars, raising the intriguing possibility that the proboscidean sample from As Sahabi contains a greater number of gomphotheriids than realised by Gaziry (1987).

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Reconsideration of the anancine molar specimens from As Sahabi suggests that their occlusal morphology is more similar to that of the advanced morph of Anancus kenyensis than previously recognised, though the apparent synapomorphy of the "tubercle de nĂŠoformation" linking As Sahabi and A. osiris molars suggests that similarities between A. petrocchii and progressive anancines from East and Central Africa are homoplasic, rather than indications of taxonomic identity. Resolution of this issue requires more careful comparative study of African anancine gomphotheres from each region. Stegotetrabelodont craniodental and postcranial specimens were assigned by Petrocchi (1943, 1954) to several different taxa: Stegotetrabelodon syrticus, S. lybicus, and the stegodontid Stegolophodon sahabianus. Gaziry (1982) accepted the presence of the latter two species, but later (1987) only recognised S. lybicus. These were all synonymised into S. syrticus by Maglio (1973), but in a footnote (p. 17) he stated that S. lybicus has page priority in Petrocchi (1941). There seems little question that Maglio (1973) was correct about the synonymy of these species, but the only mention of "libyca" in Petrocchi (1941:110) is in reference to gomphotheres from Wadi Moghara, Egypt, and thus his proposal to name the stegotetrabelodonts from As Sahabi as "Stegotetrabelodon syrticus" (p. 110) gives that nomen priority. Gaziry (1987) suggested incorporating East African S. orbus into

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(1943: figs. 70, 71) illustrated the molar to hint at the contribution of many small mammillons to the formation of each plate, these are not apparent on the specimen (Figure 4E), and instead each plate seems to be formed of four-five robust conelets. The primitiveness of the specimen is shown by the thick enamel, trace of a medial longitudinal sulcus, and its evident brachyodonty. It probably should be assigned to Elephantidae, but its specific identity is indeterminate, pending closer comparative examination. The simultaneous presence of three (or more) proboscidean megaherbivores at As Sahabi may have been sustained by niche partitioning and differential use of the landscape. Along with evidence that stegotetrabelodonts relied primarily on C4 graze, isotope analyses on anancine gomphothere tooth enamel from a number of African sites indicate that these proboscideans also had predominantly C4plant based diets (Cerling, et al., 1999 2003; Zazzo, et al., 2000, Harris, et al., 2003; Semaw, et al., 2005), suggesting that A. petrocchii as well as S. syrticus preferred wooded savanna or grassland habitats. Given the length and strong downward orientation of their upper and lower tusks, however, it is difficult to imagine how S. syrticus could have managed to forage low to the ground. It is possible that these elephants specialised in eating tall grasses, while the anancine gomphotheres were more likely groundlevel feeders (see Ferretti and Croitor, 2005). Occlusal morphology suggests that amebelodonts were browsers, and the flattened lower tusks of many amebelodont taxa is consistent with acquisition of tough or subsurface and

S. syrticus, and this proposal merits consideration. Morphological distinctions between them are minor, and it is possible that tusks of S. syrticus are longer than those of S. orbus due to ontogenetic development, as tusks are ever-growing. Conversely, fossils from Abu Dhabi that have been placed in S. syrticus, including a partial skeleton with cranium, mandible, and tusks (Andrews, 1999; Tassy, 1999) appear different enough to warrant specific separation. For example, the m3 from the Abu Dhabi sample is differentiated from S. syrticus m3 by having eight plates, with both anterior and posterior accessory conules closely appressed to several plates (Sanders, 2004). Although S. syrticus and S. orbus have been posited as good models for the ancestry of the crown elephants Loxodonta, Elephas, and Mammuthus (Maglio, 1973; Coppens et al., 1978), they may instead be part of a basal "side" radiation unrelated to the Recent lineages of elephants. The presence of anterior and posterior accessory conules in the Abu Dhabi taxon is shared with primitive representatives of these lineages, providing a better fit with the expected ancestral morphotype for crown elephants (Sanders, 2004; Sanders, et al., in press). Petrocchi (1943, 1954) also recognised a second stegodontid from As Sahabi, which he placed in Stegodon syrticus, based on a single M3. While this specimen is clearly differentiated from the stegotetrabelodont sample from the site by its possession of seven lophs and a posterior cingulum, or small eighth loph, and absence of accessory central conules, its identification as a stegodontid is questionable. Although Petrocchi

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ACKNOWLEDGEMENTS

aquatic browse (Lambert, 2002). It is likely that Amebelodon cyrenaicus lived in more forested or possibly wetter conditions than S. syrticus and A. petrocchii. Fossil wood from As Sahabi also provides evidence for the proximity of such contrasting ecosystems (Dechamps and Maes, 1987).

I thank Noel Boaz for his invitation to provide this review in recognition of the many contributions of A. Wahid Gaziry to p a l a e o n t o l o g y ( e s pe c i a l l y f o s s i l proboscideans), and the following individuals for permissions to study fossil specimens in their care: Meave Leakey and Emma Mbua (National Museums of Kenya, Nairobi), Graham and Margaret Avery (Iziko South African Museum, Cape Town), Leonard Ginsburg (Museum National d'Histoire Naturelle, Paris), Mohammed Arif (Geological Survey of Pakistan, Islamabad), Muluneh Mariam (National Museum of Ethiopia, Addis Ababa), Amandus Kweka and Michael Mbago (Tanzanian National Museums, Dar es Salaam), Ezra Musiime (Ugandan Museum, Kampala), Mohammed el-Bedawi (Cairo Geological Museum, Cairo), and particularly Jerry Hooker (The Natural History Museum, London). I am especially grateful to Bonnie Miljour (University of Michigan, Ann Arbor) for composing the figures, and to Noel Boaz for providing access to photographs of As Sahabi proboscidean specimens. Peter Robinson (University of Colorado, Boulder) provided invaluable bibliographic assistance. This research was generously supported by several Turner Grants from the Department of Geological Sciences, University of Michigan, and through grants to Terry Harrison (New York University, New York), John Kappelman (University of Texas, Austin), and Laura MacLatchy (University of Michigan, Ann Arbor).

Age Stegotetrabelodonts are well constrained temporally at East African sites to the Late Miocene-Early Pliocene (Sanders, et al., in press), and there is no reason to suspect that the species from As Sahabi is not also broadly from this time interval. The presence of a moderately advanced anancine gomphothere at the site refines age estimates to the Early Pliocene, based on morphological comparison with equally well dated anancine gomphotheres from East Africa in the Anancus kenyensis stage sequence (see Mebrate and Kalb, 1985). This age is consistent with the presence of an elephant slightly more advanced than Stegotetrabelodon. Still, the stegotetrabelodont fossils seem anomalously archaic for an Early Pliocene age assessment, especially if tusk and mandibular length differences with S. orbus are of phylogenetic, rather than ontogenetic, importance, and given somewhat greater expression of accessory conules throughout molar crowns in S. syrticus than in S. orbus. In addition, the presence of an ambelodont is unexpected for an Early Pliocene site. Amebelodon cyrenaicus from As Sahabi is the youngest occurrence of the genus (Lambert, 1990). Either the site samples more than one age, or the fauna is composed of a mix of Early Pliocene and relictual Late Miocene taxa (see Boaz, 1987; Boaz et al., this volume).

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Special Issue, No. 5

An Overview of the As Sahabi Carnivore Guild with Description of New Specimens from E.L.N.R.P. Field Surveys

LORENZO ROOK and RAFFAELE SARDELLA

ABSTRACT The study of the carnivore specimens collected during the 2006 and 2007 field surveys by the E.L.N.R.P. team at As Sahabi allows us to identify the following taxa: ?Dinofelis sp., a large-sized machairodont, cf. Agriotherium sp., and Hyaenidae indet. (different sizes). This new sample allows us to report a possible new occurrence at As Sahabi of ?Dinofelis sp., a machairodont felid first occurring in latest Miocene sites of Africa (Langenbaanweg, Lothagam) and Europe (Venta del Moro).

Lorenzo Rook, Dipartimento di Scienze della Terra, UniversitĂ di Firenze, Via G. La Pira 4, 50121 Firenze, Italy, lorenzo.rook@unifi.it Raffaele Sardella, Dipartimento di Scienze della Terra, Sapienza UniversitĂ di Roma , P. le A. Moro 4, 00185 Roma, Italy, raffaele.sardella@uniroma1.it

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Ursidae

INTRODUCTION The Sahabi Formation (Cyrenaica, Libya) has yielded a celebrated vertebrate fossil fauna (Petrocchi 1943, 1952; Boaz et al., 1987; this volume). Current faunal correlations and geological context suggest an age around ca. 6.7 ma, equivalent to the transition between the units MN12 and MN13 within the European biochronological scale. The vertebrate assemblage includes numerous remains of Carnivora, whose description has been provided in two important papers by F. C. Howell (1982, 1987) and has been recently in part updated by two punctual descriptive papers (Rook and Martinez-Navarro, 2004; Sardella and Werdelin, 2007). The aim of the present paper is to summarise the taxonomic status of the carnivore guild of the Sahabi Formation and to provide the description of the carnivore specimens collected during the latest field surveys by the ELNRP team.

Mustelidae Viverridae Hyaenidae

Felidae

Phocidae

Agriotherium cf. africanum Indarctos atticus Ursidae indet Mustelidae indet. Viverra howelli Viverridae sp. B Adcrocuta eximia Percrocuta aff. senyureki â&#x20AC;&#x153;Hyaenictitheriumâ&#x20AC;? namaquensis Chasmaporthetes sp. Hyaenidae indet. ?Paramachairodus orientalis Amphimachairodus aff. kabir ? Dinofelis sp. Felidae indet. sp. A Felidae indet. sp. B Felidae indet. sp. C Phocidae indet.

The palaeobiogeographic significance of the As Sahabi vertebrate assemblage is discussed in another paper of the present volume (Bernor and Rook, this volume). As Sahabi exhibits consistent biogeographic connections to older Late Miocene localities of Pikermian age (and to equivalent-aged Arabian and Kenyan localities) with the occurrence of some taxa of western Eurasian large mammals, as well as taxa that are uniquely Arabian and East African. The peculiarity of As Sahabi characterises this faunal assemblage as a Late Miocene biogeographic crossroads between western Eurasia and sub-Saharan Africa. As a matter of fact the carnivore guild confirms this observation. Ursidae,

The Sahabi Carnivore Guild The numerous carnivore remains from As Sahabi represent several families: Viverridae, Ursidae, Mustelidae, Hyaenidae, Felidae, and Phocidae. Howell (1987) stressed that the carnivore guild of As Sahabi is not unexpected in the context of the latest Miocene of the CircumMediterranean region. The significance of the As Sahabi carnivore assemblage (as well as that of the fauna on the whole) is its contribution to the knowledge of the little known palaeontological record of the latest Miocene biome of North Africa. At present the carnivores recognised at Sahabi are:

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in this respect to both type of A. kabir and A. aff. kabir from Sahabi by Sardella and Werdelin). (M1 length = 28,6, breadth = 24,2; P4 length = 22,3; breadth = 9,2; Mandible thickness below P4/M1 = 17,9; Diastema P3-C = 35,4). The wear of the posterior labial part of the P4 crown is “Homotherium-like.” 24P102A – Large-sized machairodont. Left IV metatarsal (Total length= 117; Distal breadth 18.3; Distal depth = 19.8; proximal breadth = 18.7; Proximal depth 19.9). Fully comparable with the same element figured by Howell (1987; Fig. 8A). 34P49A – Large-sized machairodont. Proximal part of a right fourth metacarpal (proximal breadth = 14.6; proximal depth = 19.5). Large Felidae metapodial, matching the size of a large machairodont. 32P49A – Large-sized machairodont. Distal fragment of a metapodial. (distal breadth = 18.0; distal depth = 16.8). Large Felidae metapodial, matching the size of a large machairodont.

Felidae, and Hyaenidae occur at As Sahabi with genera of relatively wide distribution. Howell (1987) noted that the Viverridae record of As Sahabi suggested an African more than European affinity. The recognition of the As Sahabi “Viverra sp. A” of Howell (1987) as a species with a circum-Mediterranean distribution (Viverra howelli, Rook and Martinez-Navarro 2004) supports this “crossroads” aspect of the Libyan assemblage. New Carnivore Material from Sahabi Formation The 2006-2007 fieldwork has been successful in the recovery of the following carnivore material: Felidae 1P201A – ?Dinofelis sp. - Left mandible bearing P4 and M1. Damaged at symphysis and without ascending ramus. The lower margin is straight without marked inferior bending anteriorly nor posteriorly (differing

Figure 1. Specimen 1P201A, ?Dinofelis sp., left mandible bearing P4 and M1; A) occlusal, B) lingual, C) labial view. Bar scale in cm. 259

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of the sample (dark brown).

12P103A – Large-sized machairodont. First phalanx, fourth digit, pes. (total length = 46.9; proximal breadth = 18.1; proximal depth = 14.8; distal breadth = 15.4; distal depth = 10.8). Large Felidae phalanx matching the size of a large machairodont.

Hyaenidae 16P25C – Hyaenidae indet. ? - Distal end of a left radius (distal breadth = 19.6; distal depth = 28.8) 102P61A – Hyaenidae indet. ? - Distal fragment (including part of the diaphysis) of a fifth (?) metatarsal (?). The diaphysis is straight (breadth at diaphysis = 8.1; depth at

Figure 2 - Specimen 24P102A, large-sized machairodont, left fourth metatarsal; A) dorsal, B) palmar, C) medial, D) lateral view. Bar scale in cm.

Ursidae 21P102A – cf. Agriotherium sp., left ulna, damaged on the proximal extremity and missing the distal end. The specimen is characterised by a marked contact area for the radius on its proximal part of the inner surface of the diaphysis and by a small and deep foramen area (distal breadth = 28.0; distal depth = 24.5). By size this specimen seems comparable to the Agriotherium from Langebaanweg. We note that the colour of this specimen (whitish) is markedly different from the aspect of most of the rest

Figure 3 - Specimen 21P102A, cf. Agriotherium sp., left ulna; A) palmar, B) lateral, C) dorsal view. Bar scale in cm. diaphysis = 1.2; distal breadth = 15.4; distal depth = 15.3). 4P99B – Hyaenidae indet.? Proximal end of

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a right radius (distal breadth = 14.2; distal depth = 18.3) 15P62A – Hyaenidae indet. (cf. Hyaenictitherium). Damaged distal end of a right humerus. The oleocranon is shallow with a small foramen (distal breadth > 35). 525P28A – Hyaenidae indet. (cf. Hyaenictitherium or Percrocuta ?). Distal portion of fifth left metacarpal. The diaphysis is straight and with round section (breadth at diaphysis = 9.8; depth at diaphysis = 1.0; distal breadth = 16.8; distal depth = 17.0). 5P25D – Hyaenidae indet. (smaller than cf. Hyaenictitherium). Damaged distal end of a left humerus. The olecranon is deep and narrow (distal breadth > 29; distal depth = 27.8). 36P24A – Carnivora indet. Fragment of humerus(?) diaphysis (breadth = 11.2; depth = 13.6) CONCLUSIONS The new carnivore sample is important. Although it does not add substantially to knowledge of the As Sahabi

Figure 4 - Specimen 5P25D, Hyaenidae indet., left humerus; A) medial, B) palmar, C) lateral, D) dorsal view. Bar scale in cm.

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carnivore guild, it does gives evidence of the occurrence of ?Dinofelis, a taxon previously not recorded at the site. The new large machairodont mandible (1P201A) shows morphologies that require a deeper comparison with the already known material from As Sahabi as well as with the type specimen of Amphimachairodus kabir. The peculiar morphology of the 1P201A mandible (the straight profile of the ventral margin, the short lower carnassial, the shape of the mandibular diastema, the tall and short symphysis, etc.) is intriguing and demands a better understanding of large machairodont variability in this Late Miocene taxon. We suggest a possible attribution to Dinofelis sp. A revision of this genus has been published by Werdelin and Lewis (2001). According to these authors the earliest record of such a felid comes from East Africa, at Lothagam (see also Werdelin, 2003). Dinofelis also occurs at Langenbaanweg (South Africa) and Venta del Moro (Spain), chronologically close to As Sahabi. Although fragmentary (and at present left without precise taxonomic assessment), the postcranial sample seems to attest to the occurrence of more than one medium to small-sized Hyaenidae. The As Sahabi small hyaenid has been reported by Esu and Kotsakis (1980) as Ictitherium arkesilai and transferred to “Hyaenictitherium” namaquense by Werdelin and Solunias (1991). A revision of the material referred to the Hyaenidae of this size range will provide new insights into this portion of the As Sahabi carnivore guild. In general terms, the fossil record of the family Hyaenidae is very well known,

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although the record of the Late Miocene of Africa is relatively under-documented. A deeper study of the As Sahabi record of the family will contribute to our understanding of the evolutionary patterns of Hyaenidae in the African continent and to compare them to the better known patterns of the Eurasian fossil record.

Geology of Sahabi. Liss, New York, 401 p. ESU, D. and KOTSAKIS, T. (1980). Ichtitherium arkesilai sp. n. (Hyaenidae, Carnivora) del terziario superiore di Sahabi (Cirenaica, Libia). Rivista Italiana di Paleontologia e Stratigrafia 86, 241-250. HOWELL , F.C. (1982). Preliminary observations on Carnivora from the Sahabi formation (Libya). Garyounis Sci. Bull. Spec. Issue 4, 49-61.

ACKNOWLEDGEMENTS We thank N. Boaz and A. ElArnauti for their energy in putting together the E.L.N.R.P. (East Libya Neogene Research Project) and for the invitation to contribute to this volume. The senior author would like to acknowledge the current structural framework for Late Miocene and Early Pliocene hominid evolution provided by the Revealing Hominid Origins Initiative funded by the National Science Foundation (NSF grant BCS-0321893) to F. Clark Howell and Timothy D. White, U.C. Berkeley. This paper is framed within a wider project on Late Neogene vertebrate evolution developed at the University of Florence (coordinator L.R.). We dedicate this paper to the memory of Prof. F. Clark Howell (19252007) for his outstanding contribution to the study of African fossil carnivores. Prof. F. Clark Howell has been in charge of the study of the As Sahabi carnivores and we regret that he left us alone in preparing this paper.

Howell, F.C. (1987) Preliminary observations on Carnivora from the Sahabi Formation. In: Neogene Paleontology and Geology of Sahabi (eds N.T. Boaz, A. ElArnauti, A.W Gaziry, J. de Heinzelin, and D.D. Boaz). Liss, New York, 153-181. PETROCCHI, C. (1943). Il giacimento fossilifero di Sahabi. Collezione Scientifica e Documentaria. A Cura del Ministero dellâ&#x20AC;&#x2122;Africa Italiana IX. A. Airoldi Editore, Verbania. PETROCCHI, C. 1952 Paleontologia de Sahabi (Cirenaica). Notizie generale sul giacimento fossilifero di Sahabi. Storia degli scavi â&#x20AC;&#x201C; Risultati. Rendiconti Accademia Nazionale dei Quaranta, Ser. IV, III, 9-33. ROOK L. and MARTINEZ-NAVARRO, B. (2004). Viverra howelli n. sp., a new viverid (Carnivora, Mammalia) from the Baccinello-Cinigiano basin (latest Miocene, Italy). Rivista Italiana di Paleontologia e Stratigrafia, Milano 110, 719-723.

REFERENCES BOAZ, N.T., EL-ARNAUTI, A., GAZIRY, A.W., DE HEINZELIN, J. and BOAZ, D.D. (eds) (1987). Neogene Paleontology and

SARDELLA, R. and WERDELIN, L. (2007). Amphimachairodus (Felidae, Mammalia)

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from Sahabi (latest Miocene â&#x20AC;&#x201C; earliest Pliocene, Libya), with a review of African Miocene Machairodontinae. Rivista Italiana di Paleontologia e Stratigrafia, Milano 113, 67-77. WERDELIN L. (2003). Mio-Pliocene Carnivora from Lothagam, Kenya In: Lothagam, The Dawn of Humanity in Eastern Africa (eds M.G. Leakey and J.M. Harris). Columbia University Press, New York, 261-314. WERDELIN, L. and LEWIS, M. E. (2001). A revision of the genus Dinofelis (Mammalia, Felidae). Zoological Journal of the Linnean Society 132, 147-258.

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Special Issue, No. 5

New Fossil Cercopithecoids from the Late Miocene of As Sahabi, Libya

BRENDA R. BENEFIT, MONTE MCCROSSIN, NOEL T. BOAZ, and PARIS PAVLAKIS ABSTRACT A preliminary revision of the fossil cercopithecoids of As Sahabi is presented based on a well-preserved right half-mandible (1P25C) with minimally worn P3-M3 and a left distal humerus (514P28A) collected in 2007. The molar teeth of 1P25C are distinguished from similarly-aged Macaca libyca (Wadi Natrun, Egypt), cf. Macaca sp. (Menacer, Algeria), and cf. Macaca sp. (Casablanca, Spain) in having M2s that are smaller, squarer, and more flared buccally. The As Sahabi papionin is distinguishable from Parapapio lothagamensis in having a less elongated and more steeply oriented mandibular symphysis, although the two monkeys share with M. libyca the presence of a P3 metaconid. Differences in size between 1P25C and some of the previously collected papionins are here attributed to dental size sexual dimorphism, although the future discovery of new material might lead to recognition of two moderately small papionins from the site. The As Sahabi papionin belongs to a new species of either Parapapio or Macaca. A newly discovered distal humerus from As Sahabi exhibits clearly cercopithecine and terrestrial features, including a strongly retroflexed medial epicondyle. It may well belong to the same species as 1P25C. A previously collected distal humerus from As Sahabi 10P61A appears to be colobine due to its well-developed lateral trochlear keel and capitulum. None of the other postcrania can clearly be assigned to subfamily due to their poor preservation. Previously collected teeth from As Sahabi all exhibit lower cusp relief and greater buccal flare than is observed in modern colobines. Given that fossil papionins from this time range have greater occlusal relief than extant cercopithecines, it is possible that only papionins are represented in the As Sahabi dental sample. Such a monkey might have had an eclectic, but predominantly frugivorous diet.

Brenda R. Benefit, Department of Sociology and Anthropology, New Mexico State University, Las Cruces, New Mexico 88003, U.S.A., bbenefit@nmsu.edu Monte McCrossin, Department of Sociology and Anthropology, New Mexico State University, Las Cruces, New Mexico 88003, U.S.A., mmccross@nmsu.edu Noel T. Boaz, International Institute for Human Evolutionary Research, Integrative Centers for Science and Medicine, 2640 Takelma Way, Ashland, Oregon 97520, U.S.A., noeltboaz@integrativemedsci.org, and Department of Anatomy, Ross University School of Medicine, P.O. Box 266, Portsmouth Campus, Roseau, Commonwealth of Dominica, nboaz@rossmed.edu.dm Paris Pavlakis, Department of Historical Geology â&#x20AC;&#x201C; Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimioupoli Zografou, 157 84 Athens, Greece, pavlakis@geol.uoa.gr

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Although their numbers are small, the North African fossils once represented much of what was known about Old World monkey evolution in Africa between 15 and 4 ma. Since 2003 the 5-8 ma deposits at Lothagam and Lemudongâ&#x20AC;&#x2122;o in Kenya and in the Middle Awash in Ethiopia have produced cercopithecoid fossils that demonstrate a greater number of species of varying body-size, locomotor, and dietary adaptations than was previously imagined (Table 1; Leakey et al., 2003; Ambrose et al., 2003; Haile-Selassie et al., 2004; Hlusko 2007a, 2007b; Frost, 2007). The papionin species Parapapio lothagamensis from the lower member of the Nawata Formation has dental traits that were unexpected for a monkey of its geologic age, combining primitive features of the Middle Miocene victoriapithecids with those characterising modern papionins (Leakey et al., 2003). The Lothagam cercopithecoid community resembles those from the North African sites which contain at least one papionin and one colobine species, and at which papionins make up a majority of the cercopithecoid fauna. In contrast, the abundant cercopithecoid fauna at the 6 ma site of Lemudongâ&#x20AC;&#x2122;o may consist entirely of three previously unknown colobine species (Hlusko, 2007a, 2007b). They demonstrate a greater diversity of body-size, dietary, and postcranial adaptations among Late Miocene Colobinae than was once predicted. A preliminary description of the new As Sahabi fossil monkeys is provided here in the context of the new eastern African discoveries and a re-examination of previously collected fossils from North Africa. Fossil cercopithecoids from

INTRODUCTION The discovery of two new wellpreserved Old World monkey specimens at As Sahabi by the East Libya Neogene Research Project during 2007 adds significantly to our knowledge of early stages in cercopithecoid evolution. Analysis of the 15 cercopithecoid specimens collected by the International Sahabi Research Project led by Boaz, Gaziry, and El-Arnauti between 1978 and 1981 indicated that they consist of at least one species of papionin referred to cf. Macaca sp. and one species of colobine monkey referred to Colobinae gen. sp. indet. (Boaz et al., 1979; Boaz and Meikle, 1982; Meikle, 1987). They are part of a larger North African cercopithecoid radiation that includes fossils from the 6-7 million-yearold sites of Menacer in Algeria (Arambourg, 1959; Thomas and Petter, 1986), Wadi Natrun in Egypt (Stromer, 1913) and Toros-Menalla in Chad (Vignaud et al., 2002). Like As Sahabi, Menacer and Wadi Natrun each preserves one papionin and one colobine monkey of moderate size (Table 1). Due to their geological age, these Late Miocene North African monkeys preserve early stages in the evolutionary history of papionins (baboons and macaques) which are estimated on the basis of molecular evidence to have diverged from cercopithecins (guenons) 11.5 million years ago. Macaque and baboon lineages are estimated to have split 7.6 million years ago. Early African Colobina are reconstructed as having split from Asian Presbytina by 9.6 million years ago (Disotell, 2000; Sterner et al., 2006; Tosi, 2005; Ting, 2007).

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Table 1. Fossil cercopithecoids from the Late Miocene of Africa, based on information in Stromer (1913), Szalay and Delson (1979), Delson (1980), Benefit and Pickford (1986),Thomas and Petter (1986), Meikle (1987), Senut (1994), Grine and Hendey (1981), Gundling and Hill (2000), Kingston et al. (2002),Vignaud et al. (2002),Leakey et al. (2003), Ambrose et al. (2003), Frost (2007), and Hlusko (2007).

NORTH AFRICA Menacer (Marceau) Wadi Natrun As Sahabi

Toros Menalla EASTERN AFRICA Ngeringerowa, BPRP #25 Nakali Mpesida, Rurmoch BPRP #85 Nawata Lower, Lothagam

Nawata Upper, Lothagam Colobinae sp. A (n=3) Colobinae sp. B (n=8) Colobinae indet (n=4) Nkondo Fm., Uganda Lukeino Lemundongâ&#x20AC;&#x2122;o

Adu Asa and lower Sangatole Formations, Ethiopia

SOUTH AFRICA Laangebaanweg

Macaca sp. (n=31) ?Colobus flandrini (n=8) Macaca libyca (n=?3) Libypithecus markgrafi (n=?3) Macaca sp. (n=6) Colobinae sp. (n=1) Cercopithecoidea indet. (n=13) Cercopithecidae

Microcolobus tugenensis (n=1) Colobinae indet (n=3) Colobinae indet (n=2) Parapapio lothagamensis (n=76) Colobinae sp. A (n=4) Colobinae sp. B (n=7) Colobinae indet (n=4) Parapapio lothagamensis (n=33)

ca. 7 ma ca. 6 ma 6-7 ma

6-7 ma

9.5-9.0 ma 9-7 ma 7-6.37 ma 6.57-7.9 ma

6.24-5.5 ma

Colobinae, 2 M3s 6.5-6.2 ma a few fragments 6.3-5.6 ma Paracolobus sp. nov 6 ma Colobinae small taxon Colobinae large taxon (n=281 total cercopithecoid) Pliopapio alemui 5.2-5.8 ma Kuseracolobus aramisi Colobinae indet (larger species) Cercopithecidae indet (small species) (n-65+ total cercopithecoid) Papionin (n=1)

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Menacer were studied at the Museum of Natural History in Paris and Macaca libyca at the American Museum of Natural History in New York.

Mandible The new mandible 1P25C is one of three known from As Sahabi (Table 2). The three mandibles are attributed to Cercopithecinae based on the morphology of their associated dentition. 1P28A preserves a corpus from symphysis to M3, but no ramus. Teeth associated with the specimen, a P3 to fully erupted M3 and canine root, are poorly preserved and missing enamel over much of their surface.

COMPARATIVE DESCRIPTION 1P25C was found at Locality P25C in January of 2007 by Paris Pavlakis. The specimen is a right half-mandible with CM2 and erupting M3 (Figure 1). The canine tip is broken, and a tiny flake of enamel is missing below the median buccal cleft of M2, but otherwise the teeth are very well

Table 2. As Sahabi cercopithecoid fossils. Attributions differ slightly from those described by Boaz and Meikle (1982) and Meikle (1987). CF.

PARAPAPIO OR MACACA SP. 1P25C Right half-mandible, male, with canine to partially erupted M3 1P28A Right half-mandible, male, with canine root to fully erupted M3 57P99A Right mandible fragment with P3 and M1 105P16A Left I1 crown 841P34A Left lower M1 514P28A Left distal humerus

Figure 1. Mandible 1P25C. Scale is 1 cm. preserved. The large canine and welldeveloped P3 honing facet indicate that the specimen is a male, and the erupting M3 indicates that it is a subadult. The M2 and P3 show very slight wear on cusp tips. The P4 and M1 are more worn with small circles of dentin exposed on buccal cusps. The mandible preserves an intact corpus from C to M3, a small portion of the lateral part of the symphysis, and a large portion of the ramus from gonial angle to about two-thirds of its height where it is broken well below the coronoid process and condyle.

COLOBINAE GEN. INDET 10P61A Left distal humerus CERCOPITHECOIDEA INDET 151P81A Right upper M2 or 3 244P16A Lingual half of right lower P4 P61A Left upper M1 collected by Jordi Agusti P61A Right lower I2 collected by Jordi Agusti 13P15A Right distal humerus 34P30A Left distal humerus 12P33A Right distal humerus 24P11A Right Proximal ulna 1P17B Right proximal end and shaft of femur 121P87A Right femoral head and neck 11P115A Left calcaneus 21P87A Proximal phalanx P61A Hallucial proximal phalanx collected by Jordi Agusti

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The size of the root and development of the P3 honing facet indicate it is a male. 57P99A preserves only the top half of the corpus from below I2 to M2 alveoli. It retains a P3 that is missing enamel buccally and a well-preserved M2 that is worn to a somewhat greater degree than that of 1P25C, with somewhat larger circles of dentine on its buccal cusps. The small size of the canine root and P3 suggest it was probably female. Of the three mandibles only 1P28A preserves the symphysis. The strong inferior transverse torus forms a distinct simian shelf that extends further posteriorly

than the superior planum as in all Cercopithecinae. The anterior aspect of the symphysis slopes at an angle of close to 38o as in Pliopapio from the Middle Awash, specimen YPM 21551 of M. libyca, and most living macaques including Macaca fascicularis (Frost, 2001). This trait differentiates the As Sahabi cercopithecines from specimen BSM I505 of Macaca libyca, Parapapio lothagamensis, and Parapapio ado which have more elongated and steeply sloping symphyses (25o to the occlusal plane of the molar teeth in P. lothagamensis according to Leakey et al 2003; Figure 2), similar to larger bodied

Figure 2. Left column: corpus and symphysis of 1P25C (center) and 1P28A (bottom); Right column: P. lothagamensis mandible KNM-LT 23091 (top), and M. libyca mandibles BSM I505 (middle) and YPM 21551 (bottom). Scale is 1 cm. 269

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1P25C 1P28A C. aethiops Gen indet mog M. fuscata M. libyca M. mulatta P. lothagamensis P. sp. Buluk V. macinnesi V3 V5b V5w 180

220

260

300

340

Corpus Height/M2 Length 1P25C 1P28A C. aethiops Gen indet mog M. fascicular M. fuscata M. libyca M. mulatta M. nemestrina P. lothagamensis P. sp. Buluk V. macinnesi V3 V5b V5w 37

Figure 3. Plots of corpus height versus M2 length and thickness for dimensions of Middle Miocene victoriapithecids (V. macinnesi) at three stratigraphic levels at Maboko Island (V3, V5b, and V5w), specimens currently attributed to Prohylobates from Wadi Moghara (Gen indet mog) and Buluk (P. sp. Buluk), Late Miocene papionins M. libyca, P. lothagamensis and As Sahabi specimens, and extant vervets (Chlorocebus aethiops) and macaques (Macaca mulatta, M. fascicularis, and M. fuscata).

Corpus Thickness/Height at M2 attributable to the subadult status and incomplete mandibular growth of 1P25C. M. libyca specimen YPM 21551 is intermediate between the two As Sahabi mandibles in terms of corpus height, but is thinner in cross-section than both specimens. The corpus of P. lothagamensis mandible KNM-LT 23901 is slightly deeper than 1P28A, although corpus height relative to M2 length corpus height of the As Sahabi, Natrun, and Lothagam specimens fall within the range observed for Macaca nemestrina. Development of a mandibular fossa is extremely slight in 1P28A and even shallower in 1P25C. This feature differentiates the As Sahabi, Lothagam, and Natrun cercopithecines from Papio,

baboons and unlike other Old World monkeys. Differences between M. libyca specimens BSM I505 and YPM 21551 are difficult to reconcile and may exceed that expected within a single taxon. The ratio of symphysis height to thickness is 117 for 1P28A, but 75.4 for M. libyca (specimen BSM I505) and 84.3 for P. lothagamensis. Values of symphyseal height to thickness for M. libyca and P. lothagamensis are closest to baboons, whereas that of 1P28A is similar to extant macaques. The mandibular corpus of 1P25C resembles that of 1P28A, but is shallower relative to both M2 length and corpus thickness at M2 (Figure 3). Differences between the two specimens fall in the range of variation of M. nemestrina, and might be

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female P3 associated with 57P99A, the length of the female P3 being only 75% that of the male. A similar relationship is found in P. lothagamensis for which the average female P3 length is 83% as large as the males. The male P3 also has a much larger honing facet (for sharpening of the upper canine) than the female. Lingually the P3s of 1P35C and 57P99A are very similar in morphology with small but distinct lingual metaconids set distal to the tip of the larger and taller protoconid (Figure 4). Metaconids are present on the P3s of P. lothagamensis, Victoriapithecus macinessi, and undescribed papionins from Taung, but do not occur in Macaca sp. from Menacer. P3 metaconids are extremely rare among

Theropithecus, Mandrillus, Gorgopithecus, and Lophocebus which have welldeveloped fossae, and makes them more similar to Parapapio and Macaca among papionins. Dentition The erupting male canine of 1P25C is the first known for a cercopithecoid from As Sahabi. It is 8.55 mm long mesiodistally, 5.43 mm wide labiolingually, and more than 12.4 mm tall to the point where the tip is broken away. These dimensions are slightly smaller than those observed for P. lothagamensis. The P3 of 1P25C is larger than the

Figure 4. P3 metaconids from lingual view on 57P99A (top) and 1P25C (bottom). Scale is 1 cm.

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proportions compare well with M1s from the site. It is treated as an M1 in this paper. The only well-preserved cercopithecoid M2s and M3s from As Sahabi are those of 1P25C. Only the M3 hypoconulid of the molars in 1P28A has intact enamel. Estimated lengths of 1P28A molars are shorter than those of 1P25C, but within the range of variation expected for a single species. Late Miocene papionins from Europe, eastern Africa, and northern Africa are all of moderate size, with those from Menacer being the largest (Table 3). M2s of M. libyca are larger than 1P25C, but As Sahabi and Natrun monkeys overlap in M1 size. M1 and M2 lengths of M. sp. from Menacer are larger than those from As Sahabi. P. lothagamensis is similar to M. libyca in M1 length, but to 1P25C in M2 length. The M1 of M. sp from the Late Miocene of Spain is just larger than that of 1P25C. The M2 of 1P25C is highly distinctive among living and fossil cercopithecoids in being more square due to its width being only slightly less than its length (L/MW=104%), and having more exaggerated buccal flare (MCP/MW=48%) (Figure 5). A rounded cingulum occurs above the cervix on the buccal cusps. Only Middle Miocene victoriapithecids, extant mangabeys, and Allenâ&#x20AC;&#x2122;s swamp monkey are similar to 1P25C in combining high M2 buccal flare with nearly square crown dimensions. Worn specimens of M. libyca approach 1P25C in shape, but are far less flared. The only unworn specimen attributed to M. libyca is much more elongated (L/MW = 120), and moderately flared (MCP/MW=53%). The majority of

modern Old World monkeys, although found on one (AMNH 19014) out of four Macaca sylvanus and in no other cercopithecine species surveyed at the American Museum of Natural History. Since no unworn P3 is known for M. libyca, its resemblance to other species is not known. On both the male and the female P3s from As Sahabi postmetacristids join the distolingual corner of the distal margin. The lingual surface of the crown of 1P25C has a deep dimple distally below the postmetacristid. The P3 of 57P99A has a similar distal lingual dimple, but it is shallower in the female. The P4 of 1P25C has a metaconid that is slightly taller than the protoconid, and is broader mesially than distally. The crown is not obliquely rotated relative to the long axis of the molar row. The P. lothagamensis P4 is described as being obliquely rotated as in V. macinnesi (Leakey et al., 2003), but examination of casts and photographs indicate that the degree to which it is oblique is slight as in many macaques, and less than that seen in victoriapithecids. As Sahabi and M. libyca P4s appear to have resembled those of P. lothagamensis in having been very slightly obliquely oriented, but the condition seems to have little phylogenetic value because it is widespread among cercopithecines. The first molar of 1P25C is the largest known from As Sahabi. In comparison, the estimated length of the M1 in mandible 1P28A is the smallest, and the M1 associated with female partial mandible 57P99A is intermediate in length (Table 3). As Sahabi specimen 841P34A was previously identified as an isolated dp4, but its length, cusp height, and overall

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Table 3. Craniodental measurements. CD=corpus depth, CT=corpus thickness, L=mesiodistal length, W=buccolingual width, CH=labial crown height, and HF=honing facet height. Measurements for P. lothagamensis are from Leakey et al. (2003).

MANDIBLE

CDP4 19 23

1P25C 1P28A 57P99A P. lothagamensis M. libyca YPM 21551 ANTERIOR TEETH

CDM2 CT M2 16.9 12.1 22.1 10.2 10.5 25.5 12.4 21.3 9.7

21.84

I1L I1W I1CH

105P16A 4.7 4.8 1P25C (male) 57P99A (female) P61A MOLAR TEETH

I2L I2W P3L P3W P3HF P4L P4W

11.6 3.5

5.4

LOWER 1P25C 57P99A 1P28A 841P34A

L 8.2 6.95 6.75 7.7

M. libyca YPM 21551 YPM 21552

7.75 6.95 7.45 8.1

6.25

13.5

MW DW 7.1 7.1 5.9 5.85 6.2

7.7 5.8

L MW 8.9 8.45

5.6 5.54

M3 ______ DW 7.5

L 11.2

MW 7.5+

DW 6.7+

8.6

10.6

7.25 7.4

9.56 8.6 8.3 9.9 9.55

13.0

9.9

9.0

5.9

cf. M. sp. Menacer Average 9.1

7.55

6.8

9.55 7.8 7.4

10.4

7.4

6.2

P. lothagamensis Average 7.6

6.2

6.4

9.0

11.4

7.7

6.8

9.1

9.4

8.0

M. sp. Almenara

7.7 7.2

6.2

6.1

UPPER 151P81A P61

6.25

6.85

6.0

M. libyca Average

7.7

8.1

7.45

9.5 9.3

8.2

cf. M. sp. Menacer Average 7.75

7.9

7.25

9.0 8.8

8.05

8.1

8.6

8.5

P. lothagamensis Average 8.0

7.8

7.6

9.2 9.3

8.8

8.9

9.1

7.2

7.15 7.1 6.6

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Lower M2 1P25C M cyclop M. arct M. fasc M. libyca M. majori M. maur M. mulatta M. nem M. nigra M. ochreata M. radia M. radiata M. silen M. sylv M. thibet M. tonkeana Menacer P. loth Figure 5. Molar indices showing degree of elongation (crown length [L]/mesial width [MW]) and buccal flare (distance between tips of mesial cusps [MCP]/ mesial width [MW])

105

115

125

MW DW Lower M2 1P25C M. fasc M. libyca M. maur M. mulatta M. nem M. nigra M. ochreata M. radia M. radiata M. silen M. sylv 90

100 274

110

120

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Lower M2 1P25C M cyclop M. arct M. fasc M. fusc M. libyca M. majori M. maur M. mulatta M. nem M. nigra M. ochreata M. radia M. radiata M. silen M. sylv M. thibet M. tonkeana Menacer P. loth 95

105

115

125

135

145

L MW

Lower M2 1P25C M. fasc M. libyca M. maur M. mulatta M. nem M. nigra M. ochreata M. radia M. radiata M. silen M. sylv M. tonkeana Menacer 40

MCP MW 275

Figure 6. Molar indices showing relative height of the metaconid (MLCH/ DLCH) and degree to which mesial width is greater than distal width (MW/ DW).

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relative to the distal lophid. Such skewing of the mesial lophid is not typical of cercopithecoid lower molars, but is seen among macaques. Occlusal relief is similarly low for the As Sahabi, Natrun, and Menacer molars and overlaps that of several macaque species and greater than that of late Miocene colobines. The sum of M2 shear crest lengths is 262% that of crown length for 1P25C as in extant Macaca fascicularis and Macaca nemestrina, indicating the As Sahabi monkey may have had a similarly frugivorous diet and that they did not feed on hard seeds like the extant mangabeys which have lower shear crest lengths. M. sp. from Menacer has higher shear crests similar to M. radiata. What is visible of the erupting M3 of 1P25C indicates that it would have had high buccal flare like the M2 and similar occlusal relief. The hypoconulid is small and centrally positioned on both 1P25C and 1P28A. Entoconid size is very small in width and crown height. In contrast entoconids are well-developed, and hypoconulids are large and positioned buccally at the end of a long and transversely oriented postentoconid in both P. lothagamensis and M. libyca.

P. lothagamensis M2s are somewhat longer relative to width, although their molars are described as being highly flared (Leakey et al. 2003). Macaca sp. from Menacer is very different from 1P25C in being elongated (L/ MW=121 on average) and having low buccal flare (MCP/MW=65%). Unworn As Sahabi M1 841P34A shows the same pattern of high buccal flare as the M2 (MCP/MW= 50.7), but is the most elongated of As Sahabi M1s (L/MW=124, range=113-124). The M1 of 1P25C is less flared due to wear (MC/MW=67), but more square (L/MW=115). M 1 s of P. lothagamensis, cf. Macaca from Menacer, the isolated M1 from Alemenara, M. sylvanus, and M. majori are more elongated but less flared than As Sahabi. Highly worn M1s of M. libyca are the squarest of the Late Miocene papionins, but the unworn M1 is more elongated (L/MW=127). Little flare (MCP/MW=72) is observed on the unworn M1s and no flare is observed on the worn M1s of M. libyca. Mesial width exceeds distal width on the M2 of 1P25C by an even greater amount than is observed in all other cercopithecoid species sampled (MW/ DW=113), and is slightly bigger than distal width for the M1. Only M1s from Menacer have even larger mesial than distal widths than is observed for As Sahabi. This difference may be related to an overall small size of the entoconid. The unworn M1 and M2 entoconids of 1P25C are much shorter and smaller than the metaconid, a condition seen in V. macinnesi, P. lothagamensis, and some extant macaques (Figure 6). Because the metaconid is positioned slightly mesial to the the protoconid, the mesial transverse lophid connecting these cusps is obliquely oriented

Other As Sahabi Teeth In addition to the new specimens, the cercopithecoid collection includes an unworn lower central incisor, 105P16A. Its very thin lingual enamel indicates that it had papionin affinities and could easily belong to the same species as 1P25A. A very worn lower lateral incisor was collected by Jordi Agusti in 1999 and is of similar size.

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Two upper molars are now known from As Sahabi, an upper right M2 (or 3) 151P81A and an upper left M2 (or 1) from P61A collected by Jordi Agusti. Both are smaller than upper molars of other North African papionins and P. lothagamensis, although they overlap in size with M1s and M3s of Mesopithecus. The tooth found by Agusti is wider than long, whereas 151P81A is as wide mesially as long. Both specimens are constricted distally with greater mesial than distal width, as in many colobine and cercopithecine species. Cusp relief on both specimens is lower than that observed in modern colobine species, but similar to that observed in the late Miocene colobines Mesopithecus and Colobus flandrini, and in many late Miocene and extant papionins. Specimen 151P85A has a

lower degree of buccal flare (MCP/ MW=69) than most papionins and late Miocene colobines. A low degree of flare is observed on worn specimens of M. libyca, but the condition in unworn specimens is unknown. M. sp. from Menacer shows more flared upper molars than 151P81A although lower molars of the species are less flared than those from As Sahabi. Nothing aligns 151P85A definitively with either Colobinae or Cercopithecinae. Distal Humerus The new As Sahabi distal humerus 514P28A (Figure 7) was collected by Noel Boaz in 2007. It exhibits cercopithecine morphological features consistent with close affinities to cercopithecines in general

Figure 7. Cercopithecid distal humeri 514P28A (A-C), 13P15A (D-F), 12P33A (G-I), 34P30A (J-L), and 10P61A (M-O) in anterior (top row), posterior (middle row), and distal (bottom row) views. Scale divisions are mm. 277

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The medial trochlear keel of 514P28A is very strongly developed so that it extends as a distinct flange distally and anteriorly. Extant colobines, in contrast, typically have a less well-developed trochlear keel. The strongly posterior orientation of the medial epicondyle of 514P28A is also like that of terrestrial cercopithecines. Extant colobine medial epicondyles are usually more medially oriented. The deep and narrow humero-ulnar articulation of semiterrestrial/terrestrial cercopithecines, tightly limiting elbow motions to flexion and extension, is mirrored in the structure of 514P28A. The new specimen also has strong development of a flange on the lateral margin of a deep olecranon fossa. This lateral flange would have articulated with a proximal extension of the anconeal process of the ulna (a condition present on 179P15A, a cercopithecine-like ulna previously collected at As Sahabi [Meikle, 1987]). Two conditions of 514P28A are unusual. First, the medial surface of the distal humerus (between the medial trochlear keel and the medial epicondyle) is marked by a very deep and well-defined fossa. Second, both the coronoid and radial fossae (but especially the former) are deeply hollowed. This latter condition is also clearly expressed in 34P30A, a much less complete cercopithecid distal humerus from As Sahabi. Most of the distal humeri from As Sahabi lack sufficient morphology to be certain which subfamily they represent. 10P61A is probably colobine because it has strong development of the lateral trochlear keel and a more spheroidal capitulum than 514P28A. 13P15A also appears to differ from other distal humeri due to its more

and, with less certainty, to papionins in particular. Overall, the 514P28A distal humerus finds its greatest resemblance with semi-terrestrial and terrestrial cercopithecoids, such as the vervet monkey (Chlorocebus aethiops), macaques, and Middle Miocene V. macinnesi. Its size is consistent with the species represented by the new mandible 1P25C as well as 1P28A from the same locality. The dimensions of 514P28A are presented in Table 4. This specimen is reasonably complete and wellpreserved in spite of some erosion. It is better preserved than the four cercopithecid distal humeri previously collected at As Sahabi (13P15A, 12P33A, 34P30A, 10P61A, see Figure 7; Meikle, 1987). The new distal humerus from As Sahabi exhibits a fundamentally cercopithecoid morphology in several respects. The medial trochlear keel is strongly developed, compared with its weaker expression in primitive catarrhines and hominoids, and projects both anteriorly and distally from the remainder of the humeral-ulnar articulation. The anterior surface of the capitulum is flattened, compared with the spheroidal convexity of the humero-radial articulation in hominoids. The medial epicondyle, which forms the area of origin of the carpal and digital flexors, is abbreviated and posteriorly oriented, compared with the longer and more medially directed medial epicondyle of hominoids. Moreover, 514P28A lacks the well-developed median (or lateral) trochlear keel and zona conoidea of hominoids. To a great extent, the cercopithecine-like features of 514P28A probably relate to adaptations for a semiterrestrial/terrestrial substrate preference.

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Table 4. Measurements of As Sahabi cercopithecoid distal humerus 514P28A

Maximum medio-lateral breadth of distal end Maximum antero-posterior thickness of distal end Antero-posterior thickness of medial trochlear keel Proximo-distal length of medial trochlear keel Maximum medio-lateral breadth of trochlea Maximum medio-lateral breadth of capitulum Medio-lateral breadth of coronoid fossa Medio-lateral breadth of radial fossa Proximo-distal length of mid-trochlea Proximo-distal length of capitulum Medio-lateral breadth of olecranon fossa Medio-lateral breadth of trochlea posteriorly Maximum antero-posterior depth of olecranon fossa Medio-lateral breadth of lateral supracondylar crest (from olecranon fossa) Orientation of medial epicondyle

24.8 15.1 12.5 12.9 ca. 11.5 ca. 8.4 7.4 4.3 7.6 9.0 9.9 9.5 7.9 8.5 71 degrees

eastern African Late Miocene species P. lothagamensis. The unusually high degree of buccal flare on the molars is sufficient to place them in a new species, but deciding whether to place it in the genus Macaca or Parapapio is more difficult to determine. In the past, placement of the North African fossil papionins into Macaca rather than Parapapio rested solely on their geographic location, primitive dentition, and the assumption that Macaca had its origins in North Africa (Delson, 1980). Fossil papionins that may be ancestral to M. sylvanus first occur at Casablanca in Spain 6 million years ago (Kohler et al., 2000). It is equally possible that the Natrun and As Sahabi specimens belong to a widespread African radiation of Miocene Parapapio. The squarish shape and the unusually high buccal flare of the As Sahabi molars and the elongated and steeply sloping symphysis of

expansive lateral trochlear keel and spheroidal capitulum. It too may have colobine affinities. The absence of a medial epicondyle makes it difficult to test whether either of these possible colobines had a more arboreal adaptation as is indicated by the more expansive trochlear keel and spheroidal capitulum. CONCLUSIONS Both the new cercopithecoid mandible and distal humerus from As Sahabi are cercopithecines and may belong to the same species. The mandible and other papionin teeth from As Sahabi are readily distinguished from fossil macaques from the site of Menacer. They are more similar to M. libyca from Wadi Natrun, although differences exist between the Natrun and As Sahabi fossils. Both have similarities to the

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M. libyca make their connection to Parapapio, especially to P. lothagamensis, highly tenable. Reexamination of previously collected specimens from As Sahabi indicates that colobines were extremely rare at the site and may only be represented by one or two postcranial elements and upper molars that are difficult to distinguish from Miocene papionins. In contrast, the complete skull of Libypithecus markgrafi from Wadi Natrun is clearly colobine and distinct from that of the European Mesopithecus. Its long shear crest and high frequency of microwear scratches on its molars indicate that Libypithecus was the oldest known committed folivore in the colobine fossil record (Reitz, 2002; Reitz and Benefit, 2001). It is more likely related to the new colobines from Lemudong’o or to the Pliocene large-bodied colobines from eastern Africa, such as Paracolobus and Rhinocolobus. If colobine, the As Sahabi upper molars exhibit a much lower degree of shearing potential and cusp relief than Libypithecus and would have consumed as many leaves as fruits, similar to the diet predicted for Mesopithecus and C. flandrini. Its affinities might have been with the Miocene colobines of Europe. More evidence is needed to test this hypothesis.

de la Carte Geologique de L’Algerie (n.s.) Paleontologie, Memoire 4, 1-159. BENEFIT, B.R. and PICKFORD, M. (1986). Miocene fossil cercopithecoids from Kenya. Am. J. Phys. Anthropol. 69, 441464. BOAZ, N.T., GAZIRY, A.W. and ELARNAUTI, A. (1979). New fossil finds from the Libyan upper Neogene site of Sahabi. Nature 280, 137-140. BOAZ, N.T. and MEIKLE, W.E. (1982). Fossil remains of Primates (Cercopithecoidea and Hominoidea) from the Sahabi Formation. Garyounis Sci. Bull., Spec. Issue 4, 41-48. DELSON, E. (1980). Fossil macaques, phyletic relationships and a scenario of deployment. In: The Macaques: Studies in Ecology, Behavior and Evolution (ed D.G. Lindburg). Van Nostrand Reinhold, New York, 10-30. D ISOTELL , T.R. (2000). Molecular systematics of the Cercopithecidae. In: Old World Monkeys (eds P.F. Whitehead and C.J. Jolly). Cambridge University Press, Cambridge, 29-56.

REFERENCES

FROST, S.R. (2001). New Early Pliocene Cercopithecidae (Mammalia: Primates) from Aramis, Middle Awash Valley, Ethiopia. American Museum Novitates 3350, 1-36.

AMBROSE, S.H., HLUSKO, L.J., KYULE, D., DEINO, A. and WILLIAMS, M. (2003). Lemudong’o: A new 6 Ma paleontological site near Narok, Kenya Rift Valley. J. Hum. Evol. 44 (6), 737-742.

FROST, S.R., HAILE-SELASSI, Y. and HLUSKO, L. (2007). Late Miocene Cercopithecidae from the Middle Awash, Afar, Ethiopia. Am. J. Phys. Anthropol. 132 (S44): 111.

ARAMBOURG, C. (1959). Vertebres continentaux du Miocene superieur de l’Afrique du Nord. Publications du Service

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GRINE, F.E. and HENDEY, Q.B. (1981). Earliest primate remains from South Africa. S. Afr. J. Sci. 77, 374-376.

from Lothagam. In: Lothagam: The Dawn of Humanity in Eastern Africa. (eds M.G. Leakey and J.M. Harris). Columbia University Press, New York, 201-248.

GUNDLING, T. AND HILL, A. (2000). Geological context of fossil Cercopithecoidea from eastern Africa. In: Old World Monkeys (eds P.F. Whitehead and C.J. Jolly). Cambridge University Press, 180-213.

M E I K L E , W.E. ( 1987) . Fos sil Cercopithecidae from the Sahabi Formation. In: Neogene Paleontology and Geology of Sahabi (eds N.T. Boaz, A. ElArnauti, A.W. Gaziry, J. de Heinzelin, and D.D. Boaz). Liss, New York, 119127.

HAILE-SELASSIE, Y., WOLDEGABRIEL, G., WHITE, T.D., BERNOR, R.L., DEGUSTA, D., RENNE, P.R., HART, W.K., VRBA, E., AMBROSE, S. and HOWELL, F.C. (2004). Mio-Pliocene mammals from the Middle Awash, Ethiopia. Geobios 37 (4), 536552.

REITZ, J.J. (2002). Dietary adaptations of Late Miocene Colobinae. Am. J. Phys. Anthropol. 34 (Suppl.) 43, 129-130. REITZ, J.J. and BENEFIT, B.R. (2001). Dental microwear in Mesopithecus pentelici from the Late Miocene of Pikermi, Greece. Am. J. Phys. Anthropol. 32 (Suppl.), 125.

HLUSKO, L.J. (2007a). A new Late Miocene species of Paracolobus and other cercopithecoid (Mammalia: Primates) fossils from Lemudong’o, Kenya. Kirtlandia 56, 72-85.

SENUT, B. (1994). Cercopithecoidea Neogenes et Quarternaires du Rift Occidental (Ouganda). In: Geology and Palaeobiology of the Albertine Rift Valley, Uganda-Zaire. Vol. II: Palaeobiology (eds B. Senut and M. Pickford). Orleans, CIFEG Occasional Publication 1994/29, 195-205.

HLUSKO, L.J. (2007b). Fossil colobines from Asa Issie Ethiopia and Lemudong’o, Kenya. Am. J. Phys. Anthropol. 132 (S44): 130. KINGSTON, J.D., JACOBS, B.F., HILL, A. and DEINO, A. (2002). Stratigraphy, age and environments of the Late Miocene Mpesida Beds, Tugen Hills, Kenya. J. Hum. Evol. 42, 95-116.

STERNER, K.N., RAAUM, R.L., ZHANG, YP, STEWART, C-B and DISOTELL, T.R. (2006). Miochondrial data support an odd-nosed colobine clade. Molecular Phylogenetics and Evolution 40, 1-7.

KOHLER, M., MOYA-SOLA, S. and ALBA, D. (2000). Macaca (Primates, Cercopithecidae) from the Late Miocene of Spain. J. Hum. Evol. 38, 447-452.

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LEAKEY, M.G., TEAFORD, M.F. and WARD, C.V. (2003). Cercopithecidae

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SZALAY, R.S. and DELSON, E. (1979). Evolutionary History of the Primates. Academic Press, New York, 580 p. THOMAS, H. and PETTER, G. (1986). Revision de la faune de mammifères du Miocene superieur de Menacer (exMarceau), Algerie: Discussion sur l’âge due gisement. Géobios 19, 357-373. T ING , N. (2007). Mitochondrial relationships and divergence dates of the African colobines: Evidence of Miocene origins for the living colobus monkeys. Am. J. Phys. Anthropol. 132 (S44), 232. TOSI, A., DETWILER, K.M. and DISOTELL, T.R. (2005). X-chromosomal window into the evolutionary history of the guenons (Primates: Cercopithecini). Molecular Phylogenetics and Evolution 36, 58-66. VIGNAUD, P., DURINGER, P., MACKAYE, H. T., LIKIUS, A., BLONDEL, C., BOISSERIE , J.-R., D E BONIS , L., EISENMANN, V., ETIENNE, M. E., GERAADS, D., GUY, F., LEHMANN, T., LIHOREAU, F., LOPEZ-MARTINEZ, N.. MOURER-CHAUVIRE, C., OTERO, O., RAGE, J. C., SCHUSTER, M., Viriot, L., Zazzo, A. and BRUNET, M. (2002). Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature 418, 152-155.

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Special Issue, No. 5

A Current View of As Sahabi Large Mammal Biogeographic Relationships RAYMOND L. BERNOR and LORENZO ROOK

ABSTRACT

As Sahabi is a latest Miocene vertebrate fauna from Libya, on the southern margin of the Mediterranean Sea. Current faunal correlations and geological context suggest an age around ca. 6.7 ma, near the transition between the biochronological units MN12 and MN13. We undertake a biogeographic comparison between As Sahabi and seven key Late Miocene localities from Central Europe, Greece, Iran, Arabia and Kenya. We find that As Sahabi exhibits consistent biogeographic connections to older Late Miocene localities of Pikermian age, circa 8.2-7.5 ma and to equivalent aged Arabian and Kenyan localities. We identify core taxa of western Eurasian large mammals that occur at As Sahabi, as well as those taxa that are uniquely Arabian and East African. The result of our study is that As Sahabi is positioned as a veritable Late Miocene biogeographic crossroads fauna between western Eurasia and sub-Saharan Africa Late Miocene faunas.

Raymond L. Bernor, National Science Foundation GEO/EAR: Sedimentary Geology and Paleobiology Program; College of Medicine, Department of Anatomy, Laboratory of Evolutionary Biology, Howard University, 520 W St. N.W., Washington DC 20059, USA, rbernor@howard.edu and rbernor@comcast.net Lorenzo Rook, Dipartimento di Scienze della Terra, UniversitĂ di Firenze, via G. La Pira, 4, 50121 Firenze, Italy, lorenzo.rook@unifi.it

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expanded over the last 10 years by M. Fortelius (NOW Director) and members of the NOW database board (Fortelius, 2005)

INTRODUCTION Bernor and Pavlakis (1987) undertook an extensive biogeographic analysis between As Sahabi and several other Eurasian and African Late Miocene and Early Pliocene vertebrate localities: 8 from western Eurasia, three from the Siwaliks of Indo-Pakistan, one from North Africa, 17 from East Africa, and one from South Africa. They used Simpson’s faunal resemblance index on mammalian genera, and submitted these scores to a cluster analysis. Analyses at the family, subfamily/ tribe, genus, and species levels found broadly congruent biogeographic patterns, but the prevailing pattern was that As Sahabi is a true crossroads fauna between Eurasian and African Late Miocene faunas. Since 1987 there have been sweeping changes in Old World large mammal systematics, geochronologic correlations, and biogeographic interpretations. Whereas members of the International Sahabi Research Project believed that there were sound reasons for correlating the fauna with the earliest Pliocene, we now believe that it is best referred to the latest Miocene, ca. 6.7 ma (Kostopoulos et al., 2003). We provide here an update of work undertaken by us (Bernor et al., 2001; Bernor and Rook, 2004; Bernor et al., 2005) on western Eurasian-African mammal evolution and biogeography. We draw upon significant advances in the development of the Neogene Old World Database (NOW; Professor Mikael Fortelius, Director; http://www.helsinki.fi/ science/now/) initially formulated from the Schloss Reisensberg Workshop (Bernor, Fahlbusch et al., 1996), and significantly

ANALYSIS AND RESULTS Our analytical procedures follow Bernor et al. (2001) for calculating Simpson’s and Dice faunal resemblance indices. Table 1 is a list of the As Sahabi large mammal fauna as we currently understand it: there are 30 species of large mammals belonging to 28 genera. Figure 1 plots genus and species homotaxis between Sahabi and selected late Miocene age localities: Rudabanya (MN9, Hungary, ca. 10 ma.; Bernor et al., 2004, 2005), Maramena (MN13, Greece, ca. 6 ma; Schmidt-Kittler [with others] et al., 1995), Middle and Upper Maragheh (MN11 and 12, Iran, ca. 8.2-7.4 ma; Bernor, Solounias, et al., 1996), Pikermi (MN11, Greece; Bernor, Solounias et al., 1996), Samos Main Bone Beds (BB; Greece, MN12; Bernor, Solounias et al., 1996), Baynunah (Abu Dhabi, MN12/13, ca. 6.7 ma; Whybrow and Hill, 1999), Lothagam Nawata (Kenya, ca. 7-5.5 ma; Leakey and Harris, 2003). Note that Bernor and Rook (2004, 2005 and herein) have made taxonomic updates and synonymies of these faunas where they found it necessary for this analysis. Figure 1 reveals that the greatest number of genera in common are with Lothagam (12), followed by Pikermi (10), then Maragheh and Samos (9), Baynunah (8) and Maramena (6). There are no genera in common between As Sahabi and Rudabánya. Rudabánya has been

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Table 1. The As Sahabi large mammal faunal list

ORDER Primates Primates Carnivora Carnivora Carnivora Carnivora Carnivora Carnivora Carnivora Carnivora Carnivora Proboscidea Proboscidea Perissodactyla Perissodactyla Perissodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla Artiodactyla

FAMILY Cercopithecidae Cercopithecidae Viverridae Ursidae Ursidae Felidae Felidae Hyaenidae Hyaenidae Hyaenidae Hyaenidae Gomphotheriidae Elephantidae Equidae Equidae Rhinocerotidae Anthracotheriidae Suidae Suidae Suidae Hippopotamidae Giraffidae Bovidae Bovidae Bovidae Bovidae Bovidae Bovidae Bovidae Bovidae

GENUS Libypithecus Macaca Viverra Agriotherium Indarctos ?Paramachairodus Amphimachairodus Adcrocuta Chasmaporthetes Hyaenictitherium Percrocuta Amebelodon [?Anancus] Stegotetrabelodon Cremohipparion "Sivalhippus" Ceratotherium Merycopotamus Nyanzachoerus Nyanzachoerus Nyanzachoerus Hexaprotodon Samotherium ?Hippotragus cf. Damalacra Gazella Leptobos Prostrepsiceros Raphicerus Redunca Tragoportax 28 Genera

SPECIES sp. sp. howelli cf. africanum atticus orientalis sp. eximia sp. namaquensis senyureki cyrenaicus lybicus sp sp neumayri petrochii cf. devauxi kanamensis syrticus sahabiensis indet. indet. indet. indet. syrticus libycus indet. cf. darti cyrenaicus 30 Species

Amphimachairodus, and Adcrocuta, the hipparionine horse Cremohipparion (small form), the rhinoceros â&#x20AC;&#x153;Ceratotheriumâ&#x20AC;? (neumayri), the bovids Gazella, Prostrepsiceros, and Tragoportax. The genera in common

demonstrated to be an endemic, central European late MN 9 fauna (Bernor et al., 2004, 2005). The core genera in common between the western Eurasian localities and As Sahabi include: the carnivores Indarctos, 285

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14 12 10 8

GIC

6 4

SIC

Ba yn Lo un th ah ag am N aw at a

Sa m

M ai n

i Pi ke rm

M &U

M ar ag he h

M ar am en

Ru da ba ny a

Figure 1 – Genus and species homotaxis between As Sahabi fauna and Eurasian, Arabian, and African localities between As Sahabi and Lothagam Nawata include: the carnivores Viverra and Hyaenictitherium, the proboscideans Anancus and Stegotetrabelodon, the rhinocerotid “Ceratotherium”, the suid Nyanzachoerus, the hippopotamid Hexaprotodon, and the bovids Tragoportax, Hippotragus, Damalacra, Gazella, Raphicerus, and Madoqua. Of these taxa, the only genera shared with the “core” western Eurasian genera included at Lothagam are the bovids Tragoportax and Gazella. Species-level homotaxis is the greatest between As Sahabi and Baynunah (4), followed by Lothagam Nawata (3),

Pikermi (3), Samos (3) and Maragheh (2). The species in common between As Sahabi and Baynunah include the proboscidean Stegotetrabelodon syrticus, the suid Nyanzachoerus syrticus, and the bovids Prostrepsiceros libycus and Tragoportax cyrenaicus; Whereas Stegotetrabelodon. syrticus (cf. Ferretti et al., 2003) and Nyanzachoerus syrticus would appear to have an Afro-Arabian origin, the two bovids, P. libycus and T. cyrenaicus, are derived from western Eurasian Pikermian forms. The species shared between As Sahabi and Lothagam Nawata include Nyanzachoerus devauxi, Nyanzachoerus syrticus, and Tragoportax 286

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cyrenaicus: all African-Arabian species. Indarctos atticus, Paramachairodus orientalis, Adcrocuta eximia, and perhaps the Amphimachairodus, all have close, arguably species-level relationships to the Pikermian faunas. Figure 2 provides genus faunal resemblance indices using both the Dice and Simpson algorithms. As pointed out by Bernor et al. (2001), the Dice index is the one most highly recommended by Archer and Maples (1987) and Maples and Archer (1988) and is calculated as: 2A / (2A + B + C), where A is the number of taxa present in both faunas, B is the number of taxa

present in fauna 1, but absent in fauna 2, and C is the number of taxa present in fauna 2 but absent in fauna 1. Simpson’s faunal resemblance index (Simpson, 1943) has a long tradition of use (Bernor, 1978; Flynn, 1986; Bernor and Pavlakis, 1987) and is calculated as: A / (A + E) where E is the smaller of B or C. Simpson’s FRI is robust and adjusts for differences in sample sizes between pair-wise faunas being considered, and this is an issue with a portion of our sample analysed herein (Simpson, 1943). We follow Bernor et al. (2001) and Bernor and Rook (2004) in plotting the Dice and Simpson’s indices together as a heuristic

0.800

Dice

0.700

Simpson

0.600 0.500 0.400 0.300 0.200 0.100

M ar am en a Ru da ba ny a

Sa m os

M B

Pi ke rm i

Ba yn un M ah ar ag he h M & U

Lo th ag am

N aw at a

0.000

Figure 2. As Sahabi biogeographic comparisons 287

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similar to the later Early-Medial Turolianaged Pikermian faunas. We deduce from these data that Pikermian faunas first occurred in the eastern Mediterranean and southerwestern Asia during the Vallesian. Pikermian faunas are known to have extended into the western Pannonian Basin (of Hungary) by the Medial Turolian, and would appear to have been in place in North Africa, Arabia, and East Africa by the Medial Turolian also. The result of our analysis confirms the earlier analysis by Bernor and Pavlakis (1987) that As Sahabi is a true Eurasian-African crossroads fauna.

comparison. Our results reveal that the highest Dice resemblance to As Sahabi is Lothagam Nawata, while the highest Simpson’s Resemblance is with Baynunah. All Dice resemblances fall between 0.350 and 0.250, while Simpson’s range from 0.500 and 0.350. CONCLUSIONS The current work has benefited from extensive new faunal studies at Rudabánya (Bernor et al., 2004, 2005), Maragheh, Pikermi and Samos (Bernor, Solounias et al., 1996), Baynunah (Whybrow and Hill, 1999) and Lothagam Hill (Leakey and Harris, 2003). We find that there are a number of western Eurasian Pikermian large mammalian carnivores and ungulate genera that occur at Sahabi. The fauna that has the most species-level similarity to As Sahabi is Baynunah, followed by Lothagam Nawata - Pikermi - Samos MBB. Maragheh is more dissimilar yet. This result suggests that As Sahabi, Baynunah, and Lothagam Nawata closely overlap chronologically. The transition between MN12 and MN13 is a likely correlation for As Sahabi and Baynunah, and correspond broadly to Lower Nawata faunas of Kenya.. As argued by Bernor and Rook (2001) and Bernor et al. (2004, 2005), strong provincial diversification occurred between Central Europe and southwestern Asia within the Vallesian. Rudabánya (northeastern Hungary; ca. 10 ma; Bernor et al., 2004) and Sinap Locality 12 (Turkey, 9.6 ma; Fortelius et al, 2003) differ across all their mammalian lineages. They have no genera in common. The Sinap Vallesian levels have a community structure very

ACKNOWLEDGEMENTS We thank N. Boaz and A. ElArnauti for their energy in putting together the ELNRP (East Libya Neogene Research Project) and for the invitation to contribute to this volume. Both authors would like to acknowledge the current structural framework for Late Miocene and Early Pliocene hominid evolution provided by the Revealing Hominid Origins Initative funded by the National Science Foundation (NSF grant BCS-0321893) to F. Clark Howell and Timothy D. White, University of California, Berkeley). Bernor would also like to thank the National Science Foundation for funding his research (currently EAR 0125009) and funding the development of the Laboratory of Evolutionary Biology at Howard University. This paper is further framed within a wider project on Late Neogene vertebrate evolution developed at the University of Florence (coordinator L.R.).

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paleoecology of the “Oreopithecus bambolii Faunal Zone (late Miocene, Tusco-Sardinian Province). Bolletino della Società Paleontologica Italiana 40 (2), 139148.

REFERENCES ARCHER A.W. and MAPLES C.G. (1987). Monte Carlo simulation of selected binomial similarity coefficients (1): Effect of number of variables. Palaios 2, 609-617.

BERNOR, R.L., KORDOS, L. and ROOK, L. (CO-EDITORS AND CONTRIBUTORS) WITH ADDITIONAL CONTRIBUTIONS BY: AGUSTI, J., ANDREWS, P., ARMOUR-CHELU, M., BEGUN, D., CAMERON, D., DAXNER HOECK, G., DE BONIS, L., DAMUTH, J., FEJFAR, O., FESSAHA, N., FORTELIUS M., FRANZEN, J., GASPARIK, M., GENTRY, A., HEISSIG, K., HERNYAK, G., KAISER, T., KOUFOS, G.D., KROLOPP, E., JANOSSY, D., LLENAS, M., MESZAROS, L., MUELLER, P., RENNE, P., ROCEK, R., SEN, S., SCOTT, R., SYNDLAR, Z., TUPAL, G., VAN DAM, J.A., WERDELIN, L., UNGAR, P.S. and ZIEGLER, R. (2004). Recent advances on multidisciplinary research at Rudabánya, Late Miocene (MN9), Hungary: A compendium. Palaeontographia Italica 89 (2002), 3-36.

BERNOR, R.L. (1978). The Mammalian Systematics, Biostratigraphy and Biochronology of Maragheh and its Importance for Understanding Late Miocene Hominoid Zoogeography and Evolution. Ph.D. dissertation, University of California, Los Angeles, 314 p. BERNOR, R.L. (1983). Geochronology and zoogeographic relationships of Miocene Hominoidea. In: New Interpretations of Ape and Human Ancestry (eds R.L. Ciochon and R. Corruccini). Plenum , New York, 21-64. BERNOR, R.L. (1984). A zoogeographic theater and biochronologic play: The time/ biofacies phenomena of Eurasian and African Miocene mammal provinces. Paleobiologie Continentale 14 (2), 121142.

BERNOR, R.L. KORDOS L. and ROOK L. (2005). Multidisciplinary research at Rudabánya. In: Multidisciplinary Research at Rudabánya (eds R.L.Bernor, L. Kordos, and L. Rook). Palaeontographia Italica 90 (2004), 1-313.

BERNOR, R.L., FAHLBUSCH, V. and MITTMANN, H.-W. (1996). The evolution of western Eurasian Neogene mammal faunas: The 1992 Schloss Reisensberg workshop concept. In: The Evolution of Western Eurasian Neogene Mammal Faunas (eds R.L Bernor, V. Fahlbusch, and H.-W Mittmann). Columbia University Press, New York, 1-6.

BERNOR, R.L. and PAVLAKIS, P. (1987). Zoogeographic relationships of the Sahabi large mammal fauna (Early Pliocene, Libya). In: Neogene Paleontology and Geology of Sahabi (eds N.T. Boaz, A. ElArnauti, A.W. Gaziry, J. de Heinzelin, and Boaz, D.D). Liss, New York, 337-348.

BERNOR, R.L., FORTELIUS, M. and ROOK L. (2001). Evolutionary biogeography and

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BERNOR, R.L. and ROOK, L. (2004). Palaeozoogeography of the Rudabánya fauna. In: Recent Advances on Multidisciplinary Research at Rudabánya, Late Miocene (MN9), Hungary: A Compendium (eds R.L. Bernor, L. Kordos, and L. Rook). Palaeontographia Italica 89 (2002), 21-25.

Paleontology of the Miocene Sinap Formation, Turkey. Columbia University Press, New York, 409 p. KOSTOPOULOS, D.S., SEN, S. and KOUFOS, G.D. (2003). Magnetostratigraphy and revised chronology of the Late Miocene mammal localities of Samos, Greece. International Journal of Earth Sciences 92, 779-794.

BERNOR, R.L., SOLOUNIAS, N., SWISHER, C.C. and VAN COUVERING, J.A. (1996). The correlation of three classical "Pikermian" mammal faunas, Maragheh, Samos and Pikermi, with the European MN unit system. In: The Evolution of Western Eurasian Neogene Mammal Faunas (eds R.L. Bernor, V. Fahlbusch and H.-W Mittmann). Columbia University Press, New York, 137-156.

LEAKEY, M. G. and HARRIS, J. M. (2003). Lothagam: Its significance and contributions. In: Lothagam: The Dawn of Humanity in Eastern Africa. (eds M.G. Leakey and J.M Harris). Columbia University Press, New York, 615-660. MAPLES, C.G. and ARCHER, A.W. (1988). Monte Carlo simulation of selected binomial similarity coefficients (II): Effect of number of sparse data. Palaios 3, 95103.

FERRETTI, M.P., ROOK, L. and TORRE, D. (2003). Stegotetrabelodon cf. syrticus (Proboscidea, Elephantidae) from the Upper Miocene of Cessaniti (Calabria, southern Italy) and its bearing on Late Miocene paleogeography of central Mediterranean. Journal of Vertebrate Paleontology 23, 659–666.

SCHMIDT-KITTLER, N. (ed.) 1995. The vertebrate locality Maramena (Macedonia, Greece) at the Turolian-Ruscinian Boundary. Muenchner Geowissenschaftliche Abhandlungen 28 (A), 1-180.

FLYNN, L. (1986). Faunal provinces and the Simpson coefficient. Contributions to Geology, University of Wyoming Special Paper 3, 317-338.

SIMPSON, C.G. (1943). Mammals and the nature of continents. Am. J. Science 241, 131.

FORTELIUS, M. (coordinator) (2005). Neogene of the Old World Database of Fossil Mammals (NOW). University of Helsinki. http://www.helsinki.fi/science/ now/. Public release 030717.

WHYBROW, P. and HILL, A. (1999). Fossil Vertebrates of Arabia. Yale University Press, New Haven, 523 p.

FORTELIUS, M., KAPPELMAN, J., SEN, S. and BERNOR, R.L. (2003). Geology and

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Special Issue, No. 5

A View to the South: Eo-Sahabi Palaeoenvironments Compared and Implications for Hominid Origins in Neogene North Africa NOEL T. BOAZ

ABSTRACT

A major Eo-Sahabi River connected the two important fossil sites of As Sahabi and Toros Menalla, Chad during the Neogene, although direct stratigraphic correlations have not yet been demonstrated. A detailed comparison of vertebrate faunas indicates that 1) Toros Menalla compares best with the Sahabi Formation upper Member U/V levels, predominantly sampled by Italian palaeontological collections in the 1930â&#x20AC;&#x2122;s. This level is younger than the Unit U-1 Sahabi Formation fauna, mainly collected since the 1970â&#x20AC;&#x2122;s; 2) the striking faunal similarities between As Sahabi and Toros Menalla indicate a distinct Libyco-Chadian or North-Central African palaeobiogeographic province in the Neogene, as previously hypothesised; and 3) both the Libyan and Chadian sites are largely open-country faunas dominated by bovids, equids, and giraffids, but with the significant presence of water-tied taxa such as anthracotheres and hippopotamids. As Sahabi preserves marine taxa, such as cetaceans, the sirenian Metaxytherium serresii, and sharks, and more abundant forest-adapted taxa, such as monkeys and an insectivore, whereas Toros Menalla preserves some more arid-adapted taxa, such as an aardvark. Faunal differences between the two sites are ascribed to 1) relatively small-scale temporal differences, 2) palaeoecological differences, 3) endemism, and 4) sampling error. The dearth of definitive hominid remains so far from As Sahabi is ascribed most likely to sampling error, although palaeoecological and temporal effects cannot be ruled out.

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INTRODUCTION

GEOLOGICAL BACKGROUND

Northern Africa is a key region, both in terms of time and palaeobiogeography, for understanding the relationships of the hominoid-bearing localities of Neogene Eurasia, the hominid-bearing localities of subSaharan Africa, and the localities in the region itself that have now yielded remains of Hominidae. In addition to Middle Pliocene Australopithecus bahrelghazali, the Late Miocene Sahelanthropus tchadensis has now been documented from Chad (Brunet et al. 2002, 2005). Boaz (1987:132) pointed out that As Sahabi was important for providing the “first indications of what role northern Africa might have played in later hominoid evolution.” Now that hominids have been clearly recognised in the region, an examination of the geological and palaecological contexts is in order so that the similarities and differences between the As Sahabi and Toros Menalla faunas can be appreciated. Correlational studies in this region have until recently been hampered by a dearth of faunas with absolute dates and a lack of clear stratigraphic control. The increasingly well-known stratigraphic and geochronological contexts of the Sahabi Formation, as documented in this volume, as well as much recently published work by the Mission Paleanthropologique FrancoTchadienne, headed by M. Brunet, now permit new analyses and new insights regarding these important palaeontological sites.

The structural depression in which the Sahabi Formation sediments were deposited is known as the Ajdabiya Trough. The trough’s Mesozoic origins long pre-date the sedimentary deposits of the Sahabi Formation and are likely related to early rifting in the central Sahara (El-Arnauti and El-Sogher, 2004:12). An arm of this rift system extended from the Gulf of Sirt in northern Libya southwards to the Chad Basin and was occupied during the latter Neogene by an inland sea, so-called “Mega Lake Chad” (Griffin, 2006, Drake et al., this volume). The Chad Basin was separated from eastern Africa by uplifted topography eventually forming the western and northern margins of the incipient Western Rift (Sepulchre et al., 2006). Mega Lake Chad flowed out to the north and gave rise to a large river, named by Griffin (2006) the Eo-Sahabi. This palaeo-river ran in a roughly parallel course some 1000 km to the west of the Nile Valley. Drake and colleagues in the current volume have demonstrated with remote imagery the course of the Eo-Sahabi from the Chad Basin to the Mediterranean up to the Pleistocene. Nicolai in this volume has illustrated with seismic data the deep channel that this river cut into basement sediments during the Mediterranean desiccation at the end of the Miocene. The geology of the Sahabi Formation and related deposits has been exhaustively investigated and reported by de Heinzelin et al. (1980), de

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the Messinian Period (ca. 6.8-5.3.ma) although the upper stratigraphic levels have not yet been intensively sampled and further work is needed to refine the upper absolute age limit of the formation. The fossiliferous sediments exposed in the Djurab Desert of northern Chad are less well-known geologically. Vignaud et al. (2002) have published the only general discussion of the geology. Deposits are grouped based on biostratigraphy into one of four major sectors, the oldest being the Toros Menalla sector. Collecting areas are extensive, being several km2 in extent and separated from one another by overlying dune sand. The low-lying topography does not afford sedimentary outcrops more than a few meters in thickness. The Toros Menalla localities have a lower 3-4-metre-thick layer of fine sands, interpreted by Schuster et al. (2006) to be aeolian dunes, which they claim to be the earliest evidence of the developing Sahara Desert. Above this level is a sandstone deposit indicated to be about 2 m thick with matrix-consolidated sands interspersed with lacustrine clays. It is informally named the “anthracotheriid unit” and is interpreted to preserve a peri-lacustrine depositional environment. All the terrestrial vertebrates, including hominids, are from this layer. A level of green, fine clayey pelite of ca. 0.5 m thickness caps the sequence and indicates full lacustrine conditions. Beryllium-10 dates on sedimentary pelites from the Chadian Toros Menalla site were recently reported by Lebatard et al. (2008). The authors quote an age bracket for the Toros Menalla fauna to be “between 6.8 and 7.2” ma, but their actual age

Heinzelin and El-Arnauti (1982) and (1987), El-Arnauti and de Heinzelin (1985), El-Shawaihdi (1995), El-Arnauti and ElSogher (2004), and authors in the present volume. Exposures of the fossiliferous Sahabi Formation are located to the west of the Sebkhat al Qunayyin. They are comprised of sands, fine clays, and sedimentary dolomites, interspersed with evaporates, such as gypsum. Overall thickness of the deposits is 80 to 100 m. The geological age of Neogene sedimentary deposits in the Ajdabiya Trough, including the Sahabi Formation, has been problematical. It is now clear from calcareous nannofossil biostratigraphy (Muftah et al., this volume) that the base of the Sahabi Formation rests on Late Miocene (Tortonian) deposits – Formations “M” and “P.” The latter formation, characterised by thick gypsum deposits, was previously interpreted to be of Messinian (terminal Miocene) age. Interpreted now as a localized lagoonal deposit and not a basinwide marker of Messinian salinity crisis desiccation, the age of Formation P is revised to be somewhat older. The overlying base of the Sahabi Formation also has a putative older maximum age, i.e. Tortonian. Now with recently reported potassium-argon analyses of sedimentary glauconite, from “Formation M” exposed at As Sahabi, and palaeomagnetic stratigraphy of the overlying sediments, Beyer in this volume dates Formation M to 7.5 to 7.7 ma and the overlying fossiliferous Sahabi Formation to between 7.3 and 7.5 ma. The Sahabi Formation thus is interpreted to be Late Miocene in age and largely earlier than

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represented within the Sahabi Formation itself, i.e. more time in the less well-known upper Sahabi Formation. Gentry in his new study of the As Sahabi bovids points out differences between the assemblage collected by the Italian teams in the 1930’s, primarily in Members U-2 and V of the Sahabi Formation (see Boaz et al., this volume), and specimens collected by field teams from the 1970’s to the present, primarily from Unit U-1 of the Sahabi Formation (Ibid.). Gentry concludes that the newly collected specimen of Miotragoceros cyrenaicus (10P103A), from U-1, shows more primitive characters than the type specimen in Rome, collected in the 1930’s, presumably from U-2. Another indication of temporal differences in the As Sahabi bovid collection is the lack in the wellsampled U-1 localities of any remains of the distinctive bovid “Leptobos” syrticus, named by Petrocchi (1956) from a specimen collected at As Sahabi in the 1930’s, also presumably from U-2. Sanders in his review of the As Sahabi proboscideans (this volume) notes that newly re-discovered fossils collected in the 1930’s are all referrable to Anancus petrocchii, a taxon not recovered in the well-sampled localities of Unit U-1. Again, these fossils derived from localities that have now been located in the areas of exposure of Members U-2 and V. They would thus appear to be later in time. The hypothesis that there was a “mixed” or diachronous fauna from As Sahabi, specifically as regards the fossils collected by the Italian teams in the 1930’s and those collected from the 1970’s onward, is not new. It was put forward by Cooke (1987) who noted that the As Sahabi

analyses (6.83 ± 0.45 and 7.12 ± 0.31) have a wider range of error, i.e. as young as 6.38 ma for the upper age limit and as old as 7.43 ma for the older. Mean age from these age determinations is 6.9 ma but with an error range of one million years (6.4-7.4 ma). BIOSTRATIGRAPHIC AGE OF THE LIBYCO-CHADIAN FAUNAS The biostratigraphic age of the fossil assemblage from As Sahabi has been debated since the inception of recent work at the site in the 1970’s. Biostratigraphic evidence initially allowed a reassessment of age to the Late Neogene, i.e. Late Miocene to Early Pliocene (Boaz et al., 1979; Bernor and Pavlakis, 1987), as opposed to earlier age attributions to older reaches of the Miocene (e.g. Petrocchi, 1951). There has been a general acceptance among researchers that the Sahabi Formation is peri-Messinian, but whether it is preMessinian, thus Late Miocene in age, postMessinian, earliest Pliocene in age, or intraMessinian, spanning a period of time at the Mio-Pliocene boundary during which the Mediterranean underwent desiccation, has been difficult to obtain consensus on. Boaz et al. (2008) summarised primarily biostratigraphic evidence and posited a Late Miocene age for the bulk of the As Sahabi vertebrate fauna, overturning an earlier consensus driven by an interpretation of lithostratigraphic evidence (see chapters in Boaz et al., 1987) that As Sahabi was basal Pliocene. Although new data and the analyses presented in this volume support this conclusion for the most part, there are also some indications that there is possible significant time

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the earliest margin of this age interval, at 7 ma. However, the recently well-dated site of Lemudong’o, Kenya also shares with Toros Menalla several biostratigraphically informative taxa, such as Anancus kenyensis and Nyanzachoerus syrticus, and it is dated to 6.1 ma (Deino and Ambrose, 2007).

suid Nyanzachoerus kanamensis, described by Leonardi (1952), appeared anomalously young compared to the suids discovered in U-1 localities (see also Gallai et al., this volume). Geraads (1989) made a similar suggestion based on his study of “Leptobos” syrticus. Dechant Boaz (1987) and Boaz (1996) both noted faunal differences between Units U-1 and U-2, e.g. an increase in the ratio to hippopotamids to anthracotheriids in U-2 compared to U-1, but ascribed these to possible ecological change or differences in habitat sampling. One reason for this interpretation was the lack of geological evidence for any major temporal hiatus at the interface of Units U-1 and U-2. There is thus evidence that suggests that a significant amount of evolutionary time separates Sahabi Formation lower Member U (with the underlying primarily marine Member T) from upper levels (upper Member U and Member V). A Late Miocene age, approximately 7 ma, is consistent with faunal studies of the U-1 fauna (Boaz et al., 2008) but the upper age boundary would appear to be younger. Further geochronological research must attempt to refine age assessments for the upper Sahabi Formation. This conclusion has implications for faunal dating of the Toros Menalla site in Chad (see below). The faunal age of Toros Menalla has been estimated by comparison of fauna from localities in the Kenyan Rift Valley with absolute dating control - Lukeino at ca. 6.0 ma and the lower Nawata Formation of Lothagam at 6.5 - 7.4 ma, cited by Vignaud et al. (2002) who suggested that Toros Menalla was between 6 and 7 ma. Brunet et al. (2004) opted to place Toros Menalla at

NEOGENE LIBYCO-CHADIAN PALAEOENVIRONMENTS There has generally been consensus on the overall palaeoenvironmental reconstruction as represented by the preserved sediments, fauna, and flora from As Sahabi. The presence of marine vertebrates and marine microfauna, especially in Member T but in higher levels as well, has been a clear indication of the proximity of shallow marine environments. Member T preserves the fossil “sirenian fields” with semi-articulated skeletons bearing bite marks of sharks (Domning and Thomas, 1987) and provides the scenario for peri-Messinian dwarfing of Metaxytherium (Ibid.; Biannucci et al, this volume). The fossil wood assemblage, and the fish, avian, herpetological, and mammalian faunas have all indicated the proximity of terrestrial habitats to a large river emptying into a low-lying system of estuaries and lagoons. Mammalian microfaunal remains, particularly the dominant presence of the gerbil, Abudhabia yardangi (Munthe, 1987; Agusti, this volume), have importantly documented the presence of arid environments inland from the water bodies. Fire-scarred fossil wood demonstrates the presence of “savanna”

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undertaken in order to assess differences and similarities. Tables 1, 2, and 3 present comparisons of the vertebrate faunas from As Sahabi and Toros Menalla. Table 1 lists the fish taxa identified at the two sites. Simpson’s Faunal Resemblance Index (FRI, see Bernor and Rook, this volume) calculated for the ichthyan fauna between the two sites is 0.72. Table 2 lists the reptilian and avian taxa from the two sites, and their FRIs are 0.9 and 0.92, respectively. Table 3 lists the relatively larger mammalian faunas, and the FRI between As Sahabi and Toros Menalla is 0.85. These are high indices of similarity and in general support the point made by numerous authors that there is a Late Neogene LibycoChadian palaeo-biogeographic region or zone (termed by Boaz 1997, “A2”, Figure 1). More detailed taxon-bytaxon comparisons are beyond the scope of this paper but in the future will provide important data on the broader regional biogeographical and, for water-tied taxa, hydrographic connections. Because As Sahabi and Toros Menalla are shown to be biostratigraphically and geochronologically close in age, differences in their faunal inventories may be ascribed to 1) small-scale temporal differences, 2) palaeoecological differences, 3) endemism, or 4) sampling error.

woodland habitats – trees with interspersed grassland (Dechamps, 1987). The mammalian fauna has a terrestrial component of bovids, equids, suids, giraffids, a rhinocerotid, proboscideans, many carnivores (dominantly hyaenids), monkeys, and an insectivore, with habitat preferences ranging from open-country to forested; a semi-aquatic component, consisting of anthracotheres, hippopotamids, and perhaps amebelodont “shovel-tuskers;” and an aquatic component with a whale, both river and salt-water dolphins, a seal, and abundant fish. The Toros Menalla vertebrate faunal assemblage is dominated by bovids (more than half) and amphibious mammals (a quarter) and has been interpreted to represent more or less open habitats (Brunet et al., 2004). The Okavango delta in Botswana has been cited as a modern habitat analogue of the peri-lacustrine mosaic of wooded habitats, wooded savanna, open savanna, and desert. One difference between Late Miocene Mega Lake Chad and the modern Okavango is, however, that the former served as the source for a major Eo-Sahabi River emptying into the Mediterranean, and the Okavango has no outlet to the sea. COMPARISON OF AS SAHABI AND TOROS MENALLA FAUNAS As Sahabi and Toros Menalla, although they share taxa with localities in other regions of Africa and Eurasia, are by far most closely similar to one another. A detailed comparison of faunas from the two sites was

Temporal Differences The proboscidean faunas argue for a temporal difference. The absence

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Table 1. Comparison of Sahabi Formation, Member U ichthyan fauna with that reported from Toros Menalla, Anthracotheriid Unit, Locality TM 266, Chad. Reference for the Sahabi Formation is Gaudant (1987) and for Toros Menalla references are Pinton et al. (2006), Otero et al. (2006, 2007), and Vignaud, et al. (2002).

SAHABI FM. U REPTILIA Crocodilia: Euthecodon sp.

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SAHABI FM. MB. U PISCES Polypteriformes: Polypterus sp. Siluriformes: Bagridae: Clarotes sp. Siluriformes: Clariidae: Clarias sp. or Heterobranchus sp. Perciformes: Lates sp. Perciformes: Sparidae indet. Mochokidae: Synodontis sp. Ariidae: Arius (?) sp.

Testudines: Trionychidae: Trionyx cf. triunguis Testudines: Testudidae: cf. Geochelone sp.

AVES Ciconiidae: Leptoptilos sp.

PISCES Polypteriformes: Polypterus faraou Siluriformes: Bagridae: “Bagrus Group” Perciformes: Indet.

Mormyriformes: Gymnarchus sp. Cypriniformes: Labeo sp. Characiformes: Sindacharax sp. Characiformes: Hydrocynus sp. Characiformes: Alestini indet. Tetraodontiformes: Tetraodon sp. Selachia: Carcaradon sp.

ANTHRACOTHERIID UNIT, TM266 REPTILIA Crocodilia: Euthecodon cf. E. nitriae Crocodilia: Gavialidae gen. et sp. nov.

Crocodilia: Crocodylus checchiai Serpentes: Booidae indet.

ANTHRACOTHERIID UNIT, TM266

Crocodilia: Crocodylus niloticus Serpentes: Python cf. P. sebae Serpentes: Colubridae indet. Lacertilia: Varanus sp. Testudines: Trionychidae indet. Testudines: Testudidae: Testudinae indet.

AVES Ciconiidae: sp. 1

Ciconiidae: Ciconiidarum gen. sp.

Ciconiidae: sp. 2

Phalacrocoracidae: Phalacrocórax sp.

Phalacrocoracidae

Anhingidae: Anhinga sp. Pelecanidae Pelecanus sp. Accipitridae: Accipitridarum gen. sp.

Anhingidae

Anatidae: Afrocygnus cf. A. chauvireae Anatidae: Anatidarum gen. sp. B Anatidae: Anatidarum gen. sp. C Anatidae: Anatidarum gen. sp. D

Anatidae: Afrocygnus chauvireae

Accipitridae

Gruidae Rallidae Heliornithidae: Heliopais cf. personata

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Table 2. Comparison of Sahabi Formation, Member U reptile and avian fauna with that reported from Toros Menalla, Anthracotheriid Unit, Locality TM 266, Chad. References for the As Sahabi fauna are Hecht, Wood, and Ballmann in Boaz et al. (1987), and for Toros Menalla Vignaud et al. (2002), Louchart, MourerChauviré et al. (2005), and Louchart, Vignaud, et al. (2005).

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Table 3. Comparison of Sahabi Formation, Member U mammalian fauna with that reported from Toros Menalla, Anthracotheriid Unit, Locality TM 266, Chad. References for Sahabi Formation are in Boaz et al. (1987) and this volume. References for Toros Menalla mammal fauna are Vignaud et al. (2002), de Bonis et al. (2005), de Bonis et al. (2007), Boisserie, Likius et al. (2005), Boisserie, Zazzo et al. (2005), Lehmann et al. (2006), Likius et al. (2007), and Peigné et al. (2005a,b). Asterisk indicates Sahabi Fm. U/V. SAHABI FM. T MAMMALIA

SAHABI FM. U MAMMALIA Primates: Cercopithecidae: Colobinae: gen. sp. Primates: Cercopithecidae: Papionini: sp. nov.

ANTHRACOTHERIID UNIT, TM266 MAMMALIA Primates: Cercopithecidae: Colobinae indet. Primates: Hominidae: Sahelanthropus tchadensis

Insectivora: Soricidae: Crocidurinae Rodentia: Xerini: cf. Atlantoxerus getulus Rodentia: Murinae: Progonomys cf. mauretanicus. Rodentia: Gerbillinae: Abudhabia yardangi Rodentia: Cricetidae: Myocricetodontinae:Myocricetodon sp. Rodentia: Ctenodactylidae: Irhoudia sp.

Rodentia: Sciuridae: Xerini: Xerus sp. Rodentia: Muridae: Murinae indet.

Rodentia: Hystricidae: Hystrix sp. Tubulidentata: Oryteropidae: Orycteropus abundulafus

Cetacea: Large, indet.

Cetacea: Delphinidae: cf. Lagenorhynchus sp. Cetacea: Platanistidae: Iniinae indet. Cetacea: Large, indet. Carnivora: Phocidae: Monachinae indet. Carnivora: Viverridae: Viverra howelli Carnivora: Hyaenidae: Hyaenictiherium sp. Carnivora: Hyaenidae: Percrocuta eximia Carnivora: Felidae: Machairodus sp.

Carnivora: Hyaenidae: Hyaenictitherium cf. H. hyanoides

Carnivora: Felidae: Machairodus kabir

Carnivora: Ursidae: Agriotherium sp. Carnivora: Ursidae: Indarctos sp.

Proboscidea: Gomphotheriidae: Anancus sp. ? * Proboscidea: Gomphotheriidae: Amebelodon cyrenaicus Proboscidea: Stegotetrabelodon syrticus

Carnivora: Mustelidae: Lutrinae indet. Carnivora: Canidae: Vulpes riffautae Carnivora: Herpestidae: Galerella sanguinae Proboscidea: Gomphotheriidae: Anancus kenyensis

Proboscidea: Loxodonta sp. aff. L. sp. indet. “Lukeino stage” Sirenia: Metaxytherium serresi

Sirenia: Metaxytherium serresi

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Table 3 (cont.) SAHABI FM. T MAMMALIA

SAHABI FM. U MAMMALIA Equidae: Hipparioninae: Cremohipparion aff. matthewi Equidae: Hipparioninae: C. nikosi Equidae: Hipparioninae: Hipparion s.s. Equidae: Hipparioninae: “Sivalhippus” Complex Rhinocerotidae: Ceratotherium neumayeri Suidae: Nyanzachoerus syrticus Nyanzachoerus cf. devauxi Nyanzachoerus kanamensis * Anthracotheriidae: Libycosaurus petrocchii Hippopotamidae: Hexaprotodon sahabiensis Giraffidae: Samotherium sp. Bovidae: Antilopini Gazella sp.

ANTHRACOTHERIID UNIT, TM266 MAMMALIA Equidae: Hipparioninae: Hipparion cf. H. abudhabiense

Suidae: Nyanzachoerus syrticus

Anthracotheriidae: Libycosaurus petrocchii

Hippopotamidae: Hexaprotodon garyam Giraffidae: Sivatherium cf. S. hendeyi Giraffidae: Bohlinia adoumi Bovidae: Antilopini Indet.

Antilopini Dytikodorcas libycus Bovini Gen. indet. “Leptobos” syrticus * Reduncinae Kobus aff. subdolus ?Hippotragus sp. Boselaphinae Miotragoceros cyrenaicus Neotragini Raphicerus sp. Alcelaphini cf. Damalacra

of Stegotetrabelodon and Amebelodon in apparently appropriate habitats at Toros Menalla coupled with the presence of Anancus and Loxodonta there, and the preponderance of Anancus only in the upper Member U/V section of the Sahabi Formation, suggests that Toros Menalla is slightly younger than the bulk of the As Sahabi fauna.

Ovibovini Indet aff. Palaeoryx Bovini Indet. Reduncini Kobus sp. cf. Hippotragini gen. et sp. indet.

number of faunal differences between the them. As Sahabi preserves a fauna representative of a range of aquatic habitats: large riverine freshwater, brackish estuarine, and lagoonal near-marine, as well as a range of terrestrial habitats: gallery forest (probably of limited extent) fringing the Eo-Sahabi River, open-country wooded grassland extending away from the river, swampy floodplain flats near water bodies, and arid near-desertic conditions distal to water bodies. Toros Menalla indicates an overall similar range of habitats but lacks or

Palaeocological Differences Palaeoecological differences between the two sites may explain a

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Figure 1. Late Neogene African biogeography. Forest refugia in Africa are indicated by extant mammalian biogeography ( regions R1, R2, and R3). Late Neogene palaeobiogeoraphic regions are indicated by regions A1-4. From Boaz (1997).

has in very small numbers 1) all marine faunal elements, such as sharks, sparid fish, sirenians, cetaceans, and seals, and 2) forest- or woodland-adapted mammalian species, such as insectivores, monkeys, and ursids. It shares with As Sahabi 1) watertied, swampy, floodplain-adapted species, such as abundant anthracotheres, which likely lived in a similar but peri-lacustrine floodplain habitat (versus riverine or estuarine floodplain at As Sahabi), and 2) more open-country-adapted species that lived away from water, including bovids, equids, giraffids, and carnivores. Toros Menalla perhaps sampled slightly more arid habitats than are preserved in the As Sahabi fauna, as indicated by the presence of termite mounds and fossils of aardvarks, both absent at As Sahabi.

Endemism The presence of two related but different species of hippoptamids — Hex. sahabiensis at As Sahabi and a larger Hex. garyam at Toros Menalla might be due to differing evolutionary adaptations to riverine and lacustrine habitats, respectively. Toros Menalla evinces the surprising discovery of a southern Asian bird species, Heliopais cf. personata, the finfoot, which probably lived in “forested margins of a freshwater body with thick overhanging vegetation” (Louchart, Mourer-Chauviré et al., 2005:7). This species may have been a relictual forest denizen isolated by surrounding open country and desert.

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Menalla fauna shares salient features with the later, U-2/V fauna. Although absolute dating still remains elusive at As Sahabi, best estimates are 7.3-7.5 ma based on recent geochronological results and ca. 7 ma based on comparative mammalian biostratigraphy for the U-1 fauna. Bernor and Rook (this volume) suggest an age for the As Sahabi fauna of 6.7 ma (MN12-13). The U-2/V fauna is younger than U-1 but by how much is difficult to ascertain until more dating analyses are done. Similarities observed between the As Sahabi U-2/V and Toros Menalla faunas indicate that the age of the fossiliferous levels at Toros Menalla, and thus the hominid Sahelanthropus tchadensis, is younger than As Sahabi U-1. Faunal differences between As Sahabi and Toros Menalla point up the proximity of marine habitats in the former. This difference is particularly pronounced in the lagoonal and estuarine Member T with its preserved mass death sites of sirenians preyed upon by great white sharks (Domning and Thomas 1987; Bianucci et al., this volume). Sahabi Formation Member U, however, also records the presence of sirenians, marine fish such as sharks and sparids, a monachine seal, and cetaceans. None of these taxa are present at Toros Menalla, at a distance of some 1100 km from the sea. The terrestrial vertebrate faunas from both Libyan and Chadian sites show significant similarlities in probable palaeohabitat representations. The water-tied components, particularly the common anthracotheres and hippotamids, indicate widespread marshy or shallow shoreline conditions. Wear on anterior teeth of anthacotheres suggests to Pickford (2006)

Sampling Error Some faunal differences between the two sites are attributed to sampling error when habitats and biostratigraphic age are deemed to have been appropriate but species are not shared. Most species of micromammals that have been discovered at As Sahabi world be expected at Toros Menalla if intensive wet-sieving had been done at that site. Brunet et al. (2004) reports that over 10,000 identified specimens have been recovered in the Toros Menalla sector. As of the end of the February-March, 2008 field season at As Sahabi, 5147 fossil specimens had been collected, identified, and catalogued. This number includes marine fauna as well as excavated specimens of taphonomic importance not unidentifiable to family, reducing the comparable number of terrestrial specimens at As Sahabi to less than 5000. With roughly twice the number of specimens collected at Toros Menalla, it would be expected that some “missing” taxa at Sahabi such as low-density carnivores (canids, lutrine otters, and mongooses), and hominids, would turn up as sample sizes increase. The liklihood that the Toros Menalla fauna is also not completely known is shown by such expected but “missing” taxa as viverrid and ursid carnivores and rhinocerotids. CONCLUSIONS AND DISCUSSION From recent discoveries and analyses from As Sahabi there is a probable temporal difference in the two fossiliferous zones of the Sahabi Formation, Members U-1 and U-2/V. It is probable that the Toros

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al., 2002). The abundant fossils of wood in the Sahabi Formation, identified by Dechamps (1987), including drifted tree trunks, record the presence of forest at As Sahabi. An insectivore (shrew) in the As Sahabi microfauna, as well as a squirrel, are likely indicators of forest habitats. There are some 20 specimens of monkeys known from As Sahabi, ascribed to a cercopithecine and colobine, whereas only one specimen, a putative colobine, is known from Toros Menalla. If monkeys are taken as general indicators of wooded to forested conditions, even though the As Sahabi cercopithecine postcrania are suggestive of terrestrial adaptations (see Benefit et al., this volume) then this is another indicator that Toros Menalla may have sampled more openhabitat conditions than As Sahabi. Permanent fresh water was present in abundance at both As Sahabi, in the form of the large Eo-Sahabi River emptying into an estuary of the paleo-Gulf of Sirt, and at Toros Menalla, where peri-lacustrine sediments on the borders of Mega-Lake Chad preserve the bulk of the fauna. Toros Menalla has yielded some half-dozen craniodental remains of the hominid Sahelanthropus while the presence of hominids at As Sahabi is still a matter of debate. As suggested here this is most likely a function of sampling error, but another possible interpretation is that the apparent greater abundance of hominids at Toros Menalla is a reflection of a biostratigraphic difference with As Sahabi, i.e. the less well known Unit U-2/V deposits at As Sahabi when investigated more fully may yet yield hominids. Alternatively, this apparent difference in hominid fossil density could be a reflection of real preferences of early

that they were feeding on soft vegetation near the shore. Hippopotamids, then as now, may indicate proximity of grassland near permanent water bodies (Boisserie, Zazzo et al., 2005). The As Sahabi proboscidean Stegotetrabelodon, with its long lower tusks, and Amebelodon, with its lower “shovel tusks,” are both thought to have employed these adaptations in procuring food by digging in soft or marshy substrates (Sanders, this volume). The absence of both these taxa at Toros Menalla might suggest that marshy habitats were less common at that site, but this interpretation is complicated by the likely temporal difference in the faunas. There are abundant taxa that record the presence of grasslands and wooded “savanna” at both As Sahabi and Toros Menalla. Bovids are common ungulates at both sites, and equids and giraffids also occur. McCrossin’s (1987) analysis of the As Sahabi Nyanzachoerus syrticus forelimb led him to postulate a “fast-running” adaptation to probable open country for this suid. A similar cursorial adaptation has been postulated for the “running hyena” Chasmaporthetes, also now known from As Sahabi (Rook and Sardella, this volume). Over half of the microfaunal assemblage at As Sahabi consists of the gerbil Abudhabia yardangi (Munthe, 1987), an indicator of semi-arid conditions. Microfauna is not fully reported from Toros Menalla but one significant indicator of semi-arid to arid conditions is the documentation of the aardvark, Orycteropus (Lehman et al., 2006). Aardvarks are not known from the As Sahabi fauna. Another indicator of aridity at Toros Menalla not known from As Sahabi is the presence of termitaries (Vignaud et

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ACKNOWLEDGEMENTS

hominids for more open, less marshy, and/ or less near-marine habitats, which seem on the evidence available so far to be better represented at Toros Menalla. Data are yet insufficient to decide between a phylogeographic model of African Rift Valley vicariance (“Hypothesis 2” of Boaz, 1997) or proto-Saharan aridification (“Hypothesis 3” of Boaz, 1997) as explanatory for early hominid origins in northern Africa. Palaeobiogeographical arguments for a Eurasian source of northern African hominoids may be improbable, but not impossible, as there are a number of Eurasian faunal elements shared between As Sahabi and Toros Menalla. A better fossil record in the Middle Miocene will be an important test for such a scenario. A differential lack of knowledge of northern African late Neogene faunas is due to demonstrable collection biases against small- to medium-sized taxa by earlier collectors, taphonomic factors affecting animals of small to medium body size, and the vast reaches of still unexplored fossiliferous exposures in northern Africa. The absence of appropriate fossil candidates for Late Miocene hominid ancestors in Africa cannot be accepted as evidence of their absence. Further research in Libya at the sites of As Sahabi and Jabal Zaltan offer opportunities to address many of these important questions. The range of non-marine palaeoenvironments reconstructed for As Sahabi is similar overall not only to the Sahelanthropus localities of Chad but also to those discovered for the early hominids of subSaharan Africa (e.g. Senut, 2006; White et al., 2006).

Research was supported by National Science Foundation grant BNS-0515591 and BCS-0321893 (two grants from the RHOI Program), Shell Exploration and Production Libya, and a faculty research grant from Ross University School of Medicine. I thank my colleagues, Ali ElArnauti and the late Abdel Wahid Gaziry for years of fruitful collaboration and friendship. The late Jean de Heinzelin and F. Clark Howell were instrumental in establishing the geological and palaeontological frameworks on which the research at As Sahabi has advanced. For all of their contributions, the members of the East Libya Neogene Research Project and the former International Sahabi Research Project are thanked, especially Paris Pavlakis, Brenda Benefit, Monte McCrossin, Ahmed El-Hawat, Fathi Salloum, Ahmed Muftah, Muftah Shawaihdi, Dimitris Michailidis, Mohamed Al Faitouri, and Naji Salini. Mustafa Salem, Giuma Anag, George and Lena Sayannos, Anders Nilsson, and Efthimia Pavlakis are thanked for their invaluable help at many stages of the work, from start to finish.

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BOISSERIE, J.-R., ZAZZO, A., MERCARON, G., BLONDEL, C., VIGNAUD, P., LIKIUS, A., MACKAYE, H.T. And BRUNET, M. (2005). Diets of modern and late Miocene hippopotamids: Evidence from carbon isotope composition and micro-wear of tooth ena mel. Palaeogeography, Palaeoclimatology, Palaeoecology 221 (2005), 153-174.

BOAZ, N.T. (1987). Sahabi and Neogene hominoid evolution. In: Neogene Palaeontology and Geology of Sahabi (eds Boaz, N.T., A. El-Arnauti, A.W. Gaziry, J. de Heinzelin, and D.D. Boaz). Liss, New York, 129-134. B O A Z , N.T. (1996). Vertebrate palaeontology and terrestrial palaeoecology of As Sahabi and the Sirt Basin. In: The Geology of Sirt Basin, Vol. 1. (eds M. Salem, A.J. Mouzughi, and O.S. Hammuda) Ámsterdam, Elsevier, 531-539.

BRUNET, M., GUY , F. , PILBEAM, D., MACKAYE, H.T., LIKIUS, A., AHOUNTA, D., B E A U V I L A I N , A., B L O N D E L , C., BOCHERENS, H., BOISSERIE, J-R., DE BONIS, L., COPPENS, Y., DEJAX, J., DENYS, C., DURINGER, P., EISENMANN, V., FANONE, G., FRONTY, P., GERAADS, D., LEHMANN, T., LIHOREAU, F., LOUCHART, A., MAHAMAT, A., MERCERON, G., MOUCHELIN, G., OTERO, O., CAMPOMANES, P., .MARCIA DE LEON, P., RAGE, P., SAPANET, J-C. , SCHUSTER, M., SUDRE, M., TASSY, J., VALENTIN, P., VIGNAUD, P. ,VIRIOT, L, and ZAZZO,C. (2002). A new hominid from the Upper Miocene of Chad, Central Africa. Nature 418, 145-151.

BOAZ, N.T. (1997). Eco Homo. New Cork, Basic, 278 p. BOAZ, N.T., EL-ARNAUTI, A., AGUSTI, A., BERNOR, R.L., PAVLAKIS, P. and ROOK, L. (2008). Temporal, lithostratigraphic, and biochronologic setting of the Sahabi Formation, North-Central Libya. In: The Geology of East Libya, vol. III. Sedimentary Basins of Libya (eds M.J. Salem, A. ElArnauti and A. El-Sogher Saleh). Earth Science Society of Libya, Tripoli. BOAZ, N.T., EL-ARNAUTI, A., GAZIRY, A. W., DE HEINZELIN, J. and BOAZ, D. D. (eds) (1987). Neogene Paleontology and Geology of Sahabi. Liss, New York, 401 p.

BRUNET, M., GUY, F., BOISSERIE, J.-R. DJIMDOUMALBAYE, A., LEHMANN, T., LIHOREAU, F., LOUCHART, A., SCHUSTER, M., TAFFOREAU, P., LIKIUS, A., MACKAYE, H.T., BLONDEL, C., BOCHERENS, H., DE BONIS, L., COPPENS, Y., DENIS, C., DURINGER, P., EISENMANN, V., FLISCH, A., GERAADS, D., LOPEZ-MARTINEZ, N., OTERO, O., PELAEZ CAMPOMANES, P., PILBEAM, D., PONCE DE LEÓN, M., VIGNAUD, P., VIRIOT, L., ZOLLIKOFER, C. (2004). “Toumaï”, Miocène supérior du Tchad, le nouveau doyen du rameau humain. C.R. Palevol. 3, 277-285.

BOAZ, N.T., A.W. GAZIRY, and A. ELARNAUTI 1979 New fossil finds from the Libyan upper Neogene site of Sahabi. Nature 280, 137-140. BOISSERIE, J.-R., LIKIUS, A., VIGNAUD, P. and BRUNET, M. (2005). A new Late Miocene hippopotamid from TorosMedalla, Chad. Journal of Vertebrate Paleontology 25(3), 665-673.

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BRUNET, M., GUY, F., PILBEAM, D., LIEBERMAN, D., LIKIUS, A., MACKAYE, H.T., PONE DE LEON, M., ZOLLIKOFER, C., and VIGNAUD, P. (2005). New material of the earliest hominid from the Upper Miocene of Chad. Nature 434, 752-755.

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