Cretaceous Research 30 (2009) 1345–1355
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Lower Cretaceous Mesoeucrocodylians from Scandinavia (Denmark and Sweden) Daniela Schwarz-Wings a, *, Jan Rees b, Johan Lindgren c a
¨ r Naturkunde, Invalidenstrasse 43, D-10115 Berlin, Germany Museum fu Soldattorpet 48, SE-653 50 Karlstad, Sweden c ¨ lvegatan 12, SE-223 62 Lund, Sweden Department of Geology, GeoBiosphere Science Centre, Lund University, So b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 January 2009 Accepted in revised form 22 July 2009 Available online 30 July 2009
The crocodyliform faunas of the lowermost Cretaceous Rabekke and Jydegård Formations on the Baltic island of Bornholm, Denmark, and the Annero Formation of Skåne, southernmost Sweden, are represented by isolated teeth, osteoderms, and vertebrae. The rich Berriasian assemblage of the Rabekke Formation includes at least three distinctive taxa: Bernissartia sp., Theriosuchus sp., and Goniopholis sp., an association that is also known from several other contemporaneous European vertebrate localities. In contrast to this fauna, the Jydegård and Annero Formations have yielded only rare mesoeucrocodylian remains, which are assigned to Theriosuchus sp. and an undetermined mesoeucrocodylian taxon, possibly Pholidosaurus. Geographically, the Scandinavian localities represent the easternmost and northernmost distribution of typical continental Jurassic-Cretaceous crocodyliform communities in Europe. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Archosauria Neosuchia Bernissartia Goniopholis Pholidosaurus Theriosuchus
1. Introduction
2. Geological setting and localities
Crocodyliform material from Scandinavia is generally scarce, with most finds comprising isolated, presumably shed teeth. Three notable exceptions are the type and a referred specimen of Thoracosaurus scanicus Troedsson, 1924 from the Danian (lower Paleocene) of southwestern Skåne (the southernmost province of Sweden) and an association of cranial elements from a single individual of Aigalosuchus villandensis Persson, 1959 from the lower Campanian of the Kristianstad Basin, northeastern Skåne. Besides representing the most complete material of ancient crocodilians from Scandinavia thus far, these specimens are the only ones that have been described formally. Nonetheless, isolated teeth, vertebrae and osteoderms are occasionally found in Cretaceous strata of southern Sweden (e.g., Siverson, 1993; Rees, 2002) and on the Danish island of Bornholm (Bonde, 2004; Lindgren et al., 2004, 2008; Rees et al., 2005). Here, we present a description of some of these remains, focusing on finds from the Berriasian-Valanginian interval of the Lower Cretaceous.
2.1. Bornholm, Denmark
* Corresponding author. E-mail address: d.schwarz-wings@museum.hu-berlin.de (D. Schwarz-Wings). 0195-6671/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2009.07.011
On the Baltic island of Bornholm, lowermost Cretaceous sediments are exposed in coastal cliff sections and a few inland quarries on the southwestern part of the island (Fig. 1). The Cretaceous strata are included in the Nyker Group and the stratigraphic sequence spans the Berriasian-Valanginian interval (Gravesen et al., 1982). This group is subdivided into three consecutive units, denominated from bottom to top the Rabekke, Robbedale, and Jydegård Formations. The sedimentary sequence begins with fluvial and limnic deposits of the Rabekke Formation, which are replaced upsection by swamp and lake sediments of the same formation. These accumulations are in turn overlain by coastal and shallow marine sands of the Robbedale Formation. Sediments at the top of the stratigraphic column are included in the Jydegård Formation, and consist primarily of back-barrier and lagoonal sands (Noe-Nygaard et al., 1987; Noe-Nygaard and Surlyk, 1988). 2.1.1. Rabekke Formation The outcrop producing crocodyliform remains is located on the south coast of Bornholm, approximately one km east of the hamlet of Arnager (Fig. 1). The sediments at this cliff section include mainly coal-rich, black clays and silts interbedded with a few distinct lensshaped beds of light grey to almost reddish clay stone. They were
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Fig. 1. Map showing the location of Bornholm and Skåne in Scandinavia and detailed maps with site information for crocodyliform-yielding localities. 1, locality in the Jydegård Formation; 2, locality in the Rabekke Formation; 3, locality in the Annero Formation.
probably deposited in a limnic environment with occasional marine influx, resulting in brackish water conditions (Petersen et al., 1996). Ostracode and palynomorph biostratigraphy indicates that the strata are early Berriasian in age, corresponding to the Runctoni ammonite Zone (Christensen, 1974; Lindgren et al., 2008, Fig. 2). A small number of lenses were sampled for microvertebrates, but only one yielded identifiable remains. In addition to teeth and bones of crocodyliforms (which are by far the most common fossils at the site), the lens has produced teeth of selachians and actinopterygians, skeletal elements of amphibians and lizards (Rees et al., 2005), carapace fragments of turtles, teeth of carnivorous dinosaurs (Lindgren et al., 2008), and a single multituberculate mammal tooth (Lindgren et al., 2004). 2.1.2. Jydegård Formation In the lower part of the uppermost Berriasian-lower Valanginian (Gravesen et al., 1982; Piasecki, 1984) Jydegård Formation (as exposed at A/S Carl Nielsen’s sand pit near Robbedale; Fig. 1) there are two bivalve and gastropod mass mortality horizons (NoeNygaard et al., 1987; Noe-Nygaard and Surlyk, 1988). Sieving of the relatively coarse sands close to these horizons yielded a rich material of vertebrates, including numerous teeth of hybodont sharks and bony fishes, two teeth of dinosaurs (Bonde and Christiansen, 2003; Christiansen and Bonde, 2003), a dentary of a small lizard (Rees, 2000), and dentary fragments of crocodyliforms.
2.2. Skåne, Sweden Lowermost Cretaceous deposits are normally not exposed in Skåne (due to a thick cover of Quaternary deposits), but in recent years have been temporarily accessed through excavations near the hamlet of Eriksdal (Fig. 1). Due to tectonic activity in the Vomb Trough (Fig. 1), the Cretaceous strata in the area are tilted and
slightly overturned (e.g., Norling et al., 1993). Sediments accumulated during the latest Jurassic and earliest Cretaceous are included in the Annero Formation, and were deposited in brackish water environments with occasional fresh water influx (e.g., Guy-Ohlson and Norling, 1994). The formation is subdivided in three consecutive members: Fyledal Clay (lower), Nytorp Sand (middle), and Vitaba¨ck Clays (Erlstro¨m et al., 1991). The precise stratigraphic position of the Jurassic-Cretaceous boundary is not known because age-diagnostic fossils are rare. However, it is assumed to be located within the lowermost part of the Vitaba¨ck Clays (Erlstro¨m et al., 1991), or, possibly, in the underlying Nytorp Sand (Vajda and Wigforss-Lange, 2006). Rare crocodyliform teeth have been recovered from three beds belonging to the Vitaba¨ck Clays, i.e. VC3, VC7 and VC11 of Rees (2002). The lower bed (VC3) contains molluscs indicative of mesohaline conditions, and the sediments may originate from a lagoonal setting (Rees, 2002). Alternatively, this part of the Vitaba¨ck Clays represents a tsunami deposit (Vajda and Wigforss-Lange, 2006). Higher up in the sequence, VC7 and VC11 were probably deposited in a small pond located further from the shoreline (Rees, 2002).
3. Material and methods Sediments dominated by silts and clays (e.g., from Rabekke) were dried, soaked in a solution of sodium carbonate and hot water, and then washed through sieves with a mesh width of 0.500 mm and 0.355 mm, respectively. Sampled coquina beds (from Vitaba¨ck) were dissolved in buffered acetic acid, and magnetic as well as density separations were undertaken in order to concentrate the vertebrate remains (for more detailed information, see Rees, 2002). All residues were searched under a binocular microscope. The coarse sands of the Jydegård Formation were wet-sieved at the locality using a net with a mesh width of 2 mm.
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Fig. 2. Teeth of Bernissartia from the Berriasian Rabekke Formation of Bornholm, Denmark. A–C, MGUH 29103, 29104 and 29105, inflated, kidney-shaped teeth in labial, lingual, lateral, and apical views. D, MGUH 29106, kidney-shaped tooth in labial, lingual, and apical views. E, MGUH 29107, button-shaped tooth, enamel partly chipped away, in labial, lingual, lateral and apical views. F, MGUH 29108, button-shaped, heavily worn tooth, from left to right in labial, lingual, and apical views. All specimens are provided as SEM photographs. Scale bars are 0.5 mm.
3.1. Institutional abbreviations BMNH; Natural History Museum, London (Former: Britisch Museum of Natural History). MGUH; Natural History Museum, Copenhagen, Denmark. LO; Department of Geology, GeoBiosphere Science Centre, Lund University, Lund, Sweden. 4. Systematic palaeontology Crocodylomorpha Walker, 1970 (sensu Clark, 1986) Crocodyliformes Hay, 1930 (sensu Clark, 1986) Mesoeucrocodylia Whetstone and Whybrow, 1983 (sensu Benton and Clark, 1988) Neosuchia Benton and Clark, 1988 Bernissartia Dollo, 1883 Bernissartia sp. indet. Fig. 2
Horizon and locality. Skyttegård Member, Rabekke Formation, Bornholm, Denmark. Material. 10 teeth (MGUH 29103 - 29108, and 4 unnumbered specimens, Natural History Museum, Copenhagen, Denmark). Description. The height and width of the tooth crowns range from 0.9 to 2.1 mm. Most of the crowns are inflated and distinctly labio-lingually compressed (Fig. 2A–D). Near the transition to the root, the base of the tooth crowns is constricted (Fig. 2A,B). In cross-section, the teeth are kidney-shaped, with a convex labial face and a slightly concave lingual surface (Fig. 2A–D). The labial and lingual faces are ornamented with apicobasally directed striae that are evenly distributed over the apical two-thirds of the crowns (Fig. 2B–D). Blunter teeth have more irregularly spaced striations, occasionally shaped as inverted ‘Y’ (Fig. 2A). The apex of unworn crowns is gently rounded (Fig. 2A,B), whereas abraded teeth possess a prominent wear-facet that is elliptical in occlusal view (Fig. 2C,D). With two exceptions (Fig. 2E,F), the teeth lack cutting edges (carinae), instead, the mesial and distal margins are broadened.
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Remarks. The dentition of Bernissartia comprises conical teeth in the rostralmost part of the snout and mandibles, broad and inflated teeth in the mid-jaws, and button-shaped teeth in the caudal part of the dental arcade (Buffetaut, 1975; Buffetaut and Ford, 1979; Brinkmann, 1992). Enamel ornamentations are largely restricted to the apical half of the tooth crowns, and range from vertical striae in kidney-shaped teeth to more or less unordered wrinkles in buttonshaped ones. The characteristic kidney-shaped tooth morphology of Bernissartia is not known from any other contemporaneous crocodylomorph, and thus the teeth from Bornholm can be confidently assigned to that genus. The teeth of Bernissartia are distinguished from those of Theriosuchus by being less labiolingually compressed, lacking distinct carinae, and possessing vertical or near vertical lingual striae. Judging from the small size of the teeth from Rabekke, they may belong to juvenile individuals (Buscalioni and Sanz,1990b). Atoposauridae Gervais, 1871 Theriosuchus Owen, 1879 Theriosuchus sp. indet. Fig. 3 Horizons and localities. Skyttegård Member, Rabekke Formation, Bornholm, Denmark, and Vitaba¨ck Clays (Bed VC3 of Rees, 2002), Annero Formation, Skåne, Sweden. Material. 284 teeth (LO 10485, MGUH 29109 - 29117, and 274 unnumbered specimens, Natural History Museum, Copenhagen, Denmark). Description. Two crown morphotypes are here assigned to Theriosuchus. The first morphotype includes 184 teeth with a lanceolate and labiolingually compressed crown shape (Fig. 3A–D). The teeth vary considerably in size; from 1 to 2 mm in basal crown length and from 1 to 4 mm in total crown height. The tooth crowns are constricted at their base, and the base itself is slightly inflated (Fig. 3B– D). Moreover, the tooth crowns bear mesial and distal carinae. The labial face of the teeth is strongly convex, and the apical half of this surface exhibits vertical striae (Fig. 3A–D). The lingual side of the crowns is weakly convex, and occasionally possesses a shallow central groove on its basal third (Fig. 3C). The enamel on this side is ornamented with more pronounced striae than on the labial face. The striations may be either closely (Fig. 3A,B) or widely (Fig. 3C,D) spaced. Whereas the striae in the central two-thirds of the tooth crowns extend more or less apicobasally, they fan out in the mesial and distal parts of the crowns to terminate at or near the carina, giving the latter a roughened appearance. The second morphotype comprises 99 teeth with mesiodistally broad crowns and a weakly convex to almost horizontal apical margin (Fig. 3E–H). There is a great size variation within this group, with both lengths and heights ranging from 1 to 3 mm. All teeth are strongly labiolingually compressed with a weak constriction near the base of the crowns. Carinae are present along the mesial and distal margins. In its lower half, the labial surface of the crowns is strongly convex, whereas the lingual surface is less so. The enamel is developed into regularly distributed striae on both the labial and lingual surfaces. The distribution of striae is similar to that of the lanceolate morphotype; on the labial side, the striae extend regularly from the base to the apex of the crowns, whereas on the lingual side, centrally located striae converge distally and terminate near the apex. Marginal striations on the lingual face are directed toward the carinae, resulting in a jagged appearance (Fig. 3E,H). Within the referred material there is also one small-sized tooth MGUH 29117 (0.8 mm in maximum length and less than 1 mm in overall height), presumably from an immature individual, that preserves large parts of the root (Fig. 3I). Although incomplete, the
preserved parts suggest that the root was originally barrel-shaped. The tooth crown is inflated at its base and labiolingually flattened. The crown is rounded in labial and lingual aspects and possesses mesial and distal carinae. The enamel forms a small number of widely spaced striae, which are more or less apicobasally directed. Remarks. The dentition of Theriosuchus includes three different morphotypes (Owen, 1879; Joffe, 1967; Brinkmann, 1992; Salisbury, 2002; Schwarz and Salisbury, 2005): (i) slender and conical teeth where the striations are largely restricted to the lingual face of the crowns, found in premaxillary, rostral-most maxillary, and rostralmost dentary positions (Owen, 1879; Brinkmann, 1992; Schwarz and Salisbury, 2005); (ii) lanceolate teeth with a fan-shaped distribution of the marginal lingual striae are found in the middle and caudal portions of the jaws (Brinkmann, 1992; Owen, 1879; Schwarz and Salisbury, 2005); and (iii) a third morphology is found in Theriosuchus pusillus and T. ibericus, where the teeth are broad and strongly labiolingually compressed, and both the lingual and labial faces are covered with striations (although fan-shaped striae are present only on the lingual face) (Owen, 1879; Brinkmann, 1989; Brinkmann, 1992; Salisbury, 2002). Generally, the morphology of the teeth of Theriosuchus varies along the dental arcade, with the lanceolate type becoming proportionately broader and slightly more rounded towards the caudal end of the jaws. Dentary teeth possess stronger striations than do maxillary teeth. In addition, there may also be some ontogenetic variation, because the striations are more strongly developed in older (larger) individuals than they are in younger (smaller) ones. The teeth from Bornholm and Skåne are assigned to Theriosuchus on the basis of their overall shape and the configuration of the striae. Whereas a lanceolate shape is commonly occurring in Theriosuchus (Owen, 1879; Joffe, 1967; Buffetaut, 1983; Brinkmann, 1989, 1992; Thies et al., 1997; Winkler, 1995; Salisbury, 2002; Schwarz and Salisbury, 2005), broad and labiolingually compressed crowns have previously been found only in T. pusillus and T. ibericus. The morphology of MGUH 29117 slightly derives from the typical tooth morphology of Theriosuchus, which may be a result of ontogeny, or it may also represent another species within the Atoposauridae, such as Montsecosuchus (Buscalioni and Sanz, 1990a). Goniopholididae Cope, 1875 Goniopholis Owen, 1842 Goniopholis sp. indet. Fig. 4A–C Horizon and locality. Skyttegård Member, Rabekke Formation, Bornholm, Denmark. Material. Five teeth (MGUH 29118 - 29120 and two unnumbered teeth, Natural History Museum, Copenhagen, Denmark). Description. Five conical tooth crowns from Rabekke are here assigned to Goniopholis. The teeth range from 1 to 4 mm in basal crown length and from 2 to 8 mm in total crown height. They are only modestly compressed labiolingually, resulting in an almost circular base (4A–C). The crowns are slightly recurved, taper apically, and end in a rounded apex. With increased size, the teeth become relatively broad and thickset; smaller teeth have a width-to-height ratio of 1:3, whereas larger teeth have a corresponding ratio of 1:2. Unserrated mesial and distal carinae are present, although they are poorly developed. The enamel forms rounded ridges that extend vertically over the entire height of the crowns, although they weaken somewhat towards the apex (Fig. 4A,C). In other teeth, the ridges are restricted to the centre of the crowns (Fig. 4B). Remarks. Teeth of Goniopholis are stout and conical, and there is little morphological change along the jaw (e.g., Hulke, 1878; Owen,
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Fig. 3. Teeth of Theriosuchus from the Berriasian Rabekke Formation of Bornholm, Denmark. A, MGUH 29109, conical, nearly lanceolate tooth, in labial, lingual, lateral, and apical views. B, MGUH 29110, lanceolate tooth, in labial, lingual, and lateral views. C–D, MGUH 29111 and 29112, lanceolate teeth, in labial, lingual, lateral, and apical views. E–F, MGUH 29113 and 29114, broadened teeth, in labial, lingual, lateral, and apical views. G, MGUH 29115, broadened tooth, in labial, lingual, and apical views. H, MGUH 29116, broadened tooth, in labial, lingual, and lateral views. I, MGUH 29117, tooth of a presumably early juvenile individual, in labial, and lingual views. All specimens are provided as SEM photographs. Scale bars for A–H are 0.5 mm, scale bar for I is 0.1 mm.
1878, 1879; Dollo, 1883; Koken, 1887; Hooley, 1907; Ortega et al., 1996; Krebs and Schwarz, 2000; Salisbury, 2002; Schwarz, 2002). The teeth are slightly labiolingually compressed, and occasionally bear weak carinae. In smaller tooth crowns, the enamel striations are coarse and well-spaced from one another, whereas they may overlap, and become weaker and/or more closely spaced on larger teeth. A small and presumably juvenile specimen referable to Goniopholis gracilidens (Salisbury, 2002) (BMNH No. 48217, ‘Nannosuchus gracilidens’ as characterized by Owen, 1879) possesses conical but slender and strongly curved teeth (Owen, 1879; Joffe, 1967), suggesting that there may be ontogenetic differences within Goniopholis. However, the specimen is considered to represent
a species different from all other described Goniopholis species from the Purbeck Formation (Salisbury, 2002). The stout proportions and coarse striations on the teeth from Bornholm suggest that they belong to Goniopholis (e.g., Owen, 1878, 1879; Krebs and Schwarz, 2000; Salisbury, 2002). The teeth are distinguishable from the more slender and finely striated teeth of Pholidosaurus, which has previously been reported from slightly younger strata on this island (Bonde, 2004), and they differ also from the needle-like and strongly recurved teeth of ‘Nannosuchus’. Mesoeucrocodylia indet. Figs. 4E–I, 5A–F
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Fig. 4. Teeth of Goniopholis from the Berriasian Rabekke Formation of Bornholm, Denmark. A, MGUH 29118, conical tooth in labial, lingual, apical, and lateral views. B, MGUH 29119, conical tooth in labial, lingual, and apical views. C, MGUH 29120, conical tooth in labial, and lingual views. D, MGUH 29127, undetermined isolated tooth of an undetermined archosaur from Bornholm, in labial, lingual, lateral, and apical views. E, MGUH 29127, undetermined conical tooth of mesoeucrocodylian from Bornholm, in labial, lingual, apical, and lateral views. Postcranial remains of mesoeucrocodylians from Bornholm. F–G, MGUH 29122 and 29123, centra of dorsal vertebrae in left lateral (above) and caudal (below) view. H, MGUH 29125, fragmentary osteoderm in external (left) and internal (right) views. I, MGUH 29124, incomplete vertebral centrum in cranial view. Specimens in A-E are provided as SEM photographs, specimens in F–I have been produced with a multi-focus camera. Scale bar for A, F, G, and I is 1 mm, scale bars for B-E are 0.5 mm, scale bar for H is 2 mm.
Horizon and locality. Skyttegård Member, Rabekke Formation, Bornholm, Denmark. Material. 180 teeth (MGUH 29121 and 179 unnumber specimens), three vertebral centra (MGUH 29122 - 29124), and 24 fragmentary osteoderms (MGUH 29125, and 23 unnumbered specimens). Description. TeethdThe tooth crowns are slender, conical and somewhat compressed labiolingually. The apex is pointed and slightly curved lingually. Weak carinae extend from the base to the apex of the crowns. The enamel is ornamented with vertical striae that increase in size and number with increased tooth size (Fig. 4E).
VertebraedThe assemblage from the Rabekke Formation includes two isolated yet virtually complete vertebral centra measuring about 4.5 mm in length (Fig. 4F,G), in addition to a partial vertebra of similar size (Fig. 4I). The parapophyses of one of the vertebrae (MGUH 29122) are positioned craniodorsally and cover the neurocentral suture (Fig. 4F), indicating that this is a cranial thoracic vertebra. The other vertebral centrum (MGUH 29123) does not possess parapophyses, and thus probably originates from the mid-thoracic region (Fig. 4G). Both vertebrae are amphicoelous with a well-developed concavity at both the cranial and caudal articular surface. The vertebral centra are hour-glass-
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Fig. 5. Teeth and osteoderm of mesoeucrocodylians from the BerriasianVitaba¨ck Clays of Skåne, Sweden. A-B, undetermined isolated teeth (LO 10485) from VC3, C, Undetermined isolated tooth (LO 10486) from VC7, D, Undetermined isolated tooth (LO 10487) from VC11. Isolated incomplete osteoderm with partial dorsal keel (LO 10488) from VC11 in E, external and F, internal view. All pictures produced with a multi-focus camera. Scale bar for A–B and D–F is 2 mm, scale bar for C is 1 mm.
shaped, and their lateral surfaces are perforated by nutritive foramina. OsteodermsdAlthough incomplete, the osteoderms probably had a sub-rectangular outline. The external surface is sculptured with circular pits (Fig. 4H), and an incomplete median keel is preserved in a few specimens. The internal surface is smooth (Fig. 4H). Remarks. Conical and striated teeth are present in the rostral portions of the jaws in Theriosuchus, Bernissartia (Dollo, 1883; Buffetaut and Ford, 1979; Buscalioni et al., 1984), and a juvenile specimen of Goniopholis (‘Nannosuchus’) gracilidens (Owen, 1879; Joffe, 1967; Salisbury, 2002). These teeth are known to vary in morphology during different ontogenetic stages, and are thus insufficient for generic determination. Although the teeth under discussion most likely originate from one or more of the above mentioned taxa, it is currently not possible to exclude affinities with other contemporary mesoeucrocodylians with slender and conical teeth, such as various thalattosuchians and pholidosaurids (Buffetaut, 1982; Hua 1997; Hua and Buffetaut, 1997; Bonde, 2004; Pouech et al., 2006). The amphicoelous vertebral centra correspond morphologically to thoracic vertebrae of Theriosuchus pusillus (Owen, 1879; Salisbury and Frey, 2001) and T. guimarotae (Schwarz and Salisbury, 2005). However, because postcrania of juvenile Goniopholis are unknown, and because the vertebrae of adult individuals possess no taxonomically useful characters (Owen, 1878; Salisbury, 2001; Schwarz, 2002), it is not possible to exclude an affinity with e.g., Goniopholis. Similarly, the thoracic vertebrae of Bernissartia (Buscalioni and Sanz, 1990b; Norell and Clark, 1990; Salisbury and Frey, 2001) are not significantly different from those of Theriosuchus. Osteoderms may be distinguished by their shape, size, presence or absence of one or two external keels, and shape of the cranial articular peg. However, because none of these characters are preserved in the osteoderms from Rabekke, an unambiguous taxonomic assignment is currently not possible. Horizon and locality. Tornhøj Member, Jydegård Formation, Bornholm, Denmark. Material. Nine mandibular fragments (MGUH 29126), presumably from a single individual. Description. The fragments are all of comparable size and likely to originate from a single mandible, although they do not fit together. The most complete specimen (preserved length is 45 mm) is a post-symphyseal dentary fragment with two alveoli. As preserved, it is 19 mm high, although the bone is incomplete ventrally. The dorsal and lateral margins are straight. Two alveoli
are widely separated from one another and are sub-circular in outline. The broken fragment of a tooth is visible in one of the alveoli, exposing a circular tooth base with a medially open pulp cavity. The lateral surface of the bone is sculptured with shallow, longitudinally directed grooves, whereas the medial face is broken off, exposing parts of the Meckelian canal and the bases of the dentary alveoli. Remarks. There are no taxonomically useful characters preserved in the mandibular material, rendering it impossible to determine whether it belongs to a large individual of one of the crocodyliforms described above, or represent another, larger taxon. Horizon and locality. Vitaba¨ck Clays (Bed VC3, VC7 and VC11 of Rees, 2002), Annero Formation, Skåne, Sweden. Material. Four teeth (LO 10485–10487) and two osteoderms (LO 10488, and one unnumbered specimen, Department of Geology, Lund University). Description. TeethdThree conical, pseudocaniniform teeth have been found in VC3. Two of the teeth include parts of the root (Fig. 5A,B), whereas the third, and much smaller specimen, only comprises the crown. The smallest tooth crown has a basal diameter of 1 mm and a height of 2 mm, while the two larger teeth measure 3 mm in basal diameter and 8 mm in height. The tooth crowns are curved medially and lack basal constrictions. They are somewhat compressed mesiodistally. The teeth taper apically and end in a narrow yet rounded apex, which is clearly offset from the rest of the crown. Carinae are weakly developed on the distal (?) margin of the crowns. The enamel forms distinct ridges, which are widely spaced and extend apicobasally. At the base of the tooth, the ending of the glossy enamel marks the transition to the root. A tooth crown with a similar morphology was found in VC11 (Fig. 5D), in addition to a very small (2 mm high) conical tooth that lacks striations. An incomplete conical tooth crown (apex missing) with a height of 5 mm was found in VC7. The crown is stout and bears mesial and distal carinae (Fig. 5C). With the exception of a few wrinkles on the apical half of the crown, the enamel is virtually smooth. OsteodermsdTwo incomplete and externally sculptured dorsal osteoderms are morphologically similar to the corresponding elements from the Rabekke Formation. One of the specimens appears to have had an oval outline, indicating that it is a caudal, or possibly a nuchal osteoderm. The other osteoderm has a sub-rectangular shape and possesses remnants of a medial keel, suggesting that it is part of a dorsal or caudal osteoderm (Fig. 5E,F). The internal surface is smooth in both specimens. Remarks. The isolated conical teeth from the Vitaba¨ck Clays can, because of their stoutness, the presence of coarse striae, distal
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carinae and a distinct smooth tip, be excluded from Pterosauria. The presence of carinae and the widely spaced striations excludes them also from Plesiosauria. The isolated teeth resemble a tooth tentatively assigned to Pholidosauridae by Bonde (2004). However, there are some differences with respect to the coarseness and amount of the striae, which prevent a confident assignment. Archosauriformes Gauthier, 1986 Archosauria Cope, 1869 Archosauria indet. Fig. 4D Horizon and locality. Skyttegård Member, Rabekke Formation, Bornholm, Denmark. Material. One tooth (MGUH 29127). Description. The tooth crown has a length of 2.2 mm and a height of 1.6 mm. It is strongly compressed labiolingually and has a leafshaped lateral outline with convex mesial and distal margins (Fig. 4D). The carinae are limited to the apical two-thirds of the crown and bear distinct denticles. In occlusal view (Fig. 4, right hand illustration), the cutting edge is flexed labially and lingually into an ‘S’-shaped structure. The apex of the crown is formed by an enlarged denticle. The base of the tooth crown is inflated and less constricted than in the teeth described above. The enamel is smooth. Remarks. MGUH 29127 cannot be unambiguously assigned to any known mesoeucrocodylian. Denticulated carinae occur also in a number of archosaurian groups including ziphosuchian crocodyliforms, some Triassic pterosaurs (Dalla Veccia, 2003) and dinosaurs (e.g., Farlow et al., 1991; Holtz et al., 1998; Ortega et al., 2000). In contrast, some other vertebrate groups, such as varanids and mosasaurid squamates and fishes, possess carinae with fine serrations, but no distinct denticles are formed at the cutting edges (compare e.g., Jagt et al., 2005). Triassic basal archosaurs such as Euparkeria (Ewer, 1965), erythrosuchids (e.g., Modesto and BothaBrink, 2008), phytosaurs (e.g., Hungerbu¨hler, 2000), or rauisuchians (e.g., Nesbitt, 2005) can be ruled out because of their considerably older appearance and different, blade-like tooth morphology. Theropod dinosaurs can equally be ruled out by their significant differences in tooth morphology (Farlow et al., 1991; Abler, 1992; Holtz et al., 1998), which is also the case for the leafshaped, denticulate teeth of prosauropods (e.g., Barrett, 2000). The overall crown morphology and regular denticles are consistent with teeth of the ornithischian (?) dinosaur Pekinosaurus (Hunt and Lucas, 1994). However, this taxon is reported from the Upper Triassic of North Carolina (USA), and is therefore considerably older than the specimen from Bornholm. Among non-eusuchian mesoeucrocodylians, denticulated serrated teeth occur in Theriosuchus ibericus (Brinkmann 1989, 1992), Dakosaurus andiniensis (Gasparini et al., 2006), and in the Ziphosuchia (Ortega et al., 2000). The overall shape and serration profile of MGUH 29127 corresponds roughly with those of T. ibericus and the ziphosuchian ‘‘Araripesuchus’’ wegeneri (Ortega et al., 2000) from the Lower Cretaceous of Niger, although it lacks enamel striations. It is thus possible that MGUH 29127 represents a taxon distinct from the other described crocodyliforms, another species of Theriosuchus, or an unidentified ziphosuchian. 5. Taphonomy and size estimates The majority of the crocodyliform teeth from the Rabekke Formation and Vitaba¨ck Clays are well preserved and show little or no sign of transportation. However, they lack roots and have often worn and broken apices, indicating that they were lost during the normal process of tooth replacement (Kieser et al., 1993). The
presence of replacement teeth indicates that the localities were situated close to the habitat of these crocodyliforms. A few teeth show some abrasion, suggesting that they were transported over some distance. Transportation may also have damaged the vertebrae by separating, at least in immature individuals, the neural arches from the centra. However, the method of collecting these fossils by sieving and chemical preparation might also have contributed to abrasion and breakage. It is thus possible that parts of the material at hand were embedded after a short transportation from the surrounding environment, and other parts were embedded within the environment. The crocodyliform teeth and bones from the Rabekke Formation are generally small and cannot have belonged to animals larger than about 60 cm in total body length. This is in accordance with the estimated size range of Theriosuchus, which reached a length of about 50 cm (Schwarz and Salisbury, 2005), and Bernissartia, with a body length of some 60 cm (Salisbury, 2001). The recovered material suggests that both taxa are probably represented by both juvenile and adult individuals. In contrast, Goniopholis could attain body lengths in excess of three metres (Salisbury, 2001), and consequently this taxon must be represented by juveniles only. The absence of adult specimens of Goniopholis may be a result of environmental specificity linked to dietary changes from juvenile to adult animals (Cott, 1961; Trutnau, 1994), or could be a result of taphonomic factors. 6. Palaeobiogeography The crocodyliform assemblages from Bornholm and Skåne are similar in their composition of more than two fossil crocodyliform taxa (i.e., Bernissartia, Theriosuchus, Goniopholis and additionally, small-sized taxa or a larger taxon such as Pholidosaurus) to a number of contemporaneous faunas of west-central Europe (Fig. 6), including: (1) Guimarota in Leiria, Portugal; ‘‘Guimarota-Strata’’ of the Alcobaça-Formation, Kimmeridgian (Upper Jurassic). Partial skeletons and isolated dental and skeletal elements of Machimosaurus hugii (Krebs, 1967, 1968), Bernissartia sp. (Brinkmann, 1989), Lisboasaurus estesi (Buscalioni et al., 1996), Goniopholis baryglyphaeus (Schwarz, 2002), Lusitanisuchus mitracostatus (Schwarz and Fechner, 2004), and Theriosuchus guimarotae (Schwarz and Salisbury, 2005). (2) Langenberg/Oker in northwestern Germany; Langenberg Formation (Kimmeridgian). Partial skeletons of Theriosuchus, Goniopholis, Machimosaurus, and Steneosaurus (Thies et al., 1997; Thies and Broschinski, 2001; Karl et al., 2006). (3) Andre`s in Pombal, Portugal; Alcobaça-Formation (Kimmeridgian–Tithonian). Isolated skeletal remains of Theriosuchus sp. and Goniopholis sp. (Malafaia et al., 2006). (4) Boulogne-sur-Mer and Wimille, Boulonnais, France; Formations gre´seuses, ‘‘Montrouge’’ and ‘‘LaRochette II’’ (Tithonian/ Portlandian). Teeth and incomplete bones of Goniopholis cf. simus (Sauvage, 1874, 1882; Buffetaut, 1986; Salisbury et al., 1999) and Theriosuchus sp. (Cuny et al., 1991). (5) Swanage, Dorset, Great Britain (several localities); Purbeck Limestone Group, ‘Beckles residuary marls’ (Salisbury, 2002) (Berriasian). Partial skeletons and isolated teeth and bones of Theriosuchus pusillus, Goniopholis crassidens, G. simus, Pholidosaurus purbeckensis (Salisbury, 2002), cf. Bernissartia (Owen, 1878, 1879; Salisbury, 2002), and cf. Lisboasaurus (Evans, 1994). (6) Cherves-de-Cognac, France; Gypsum and marlstone units equivalent to Purbeck Limestone Group (Berriasian). Skeletons of Theriosuchus spp., Goniopholis simus, G. crassidens, a single
D. Schwarz-Wings et al. / Cretaceous Research 30 (2009) 1345–1355
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Fig. 6. Geographic map with Upper Jurassic and Lower Cretaceous localities yielding mesoeucrocodylian communities with Goniopholis, Theriosuchus, and Bernissartia. Numbers refer to section 6, Palaeobiogeography; crosses refer to the localities on Bornholm and SkĂĽne described in this paper.
(7)
(8)
(9)
(10) (11)
(12)
skull of Pholidosaurus purbeckensis, isolated mandible of Bernissartia fagesi, isolated teeth of these taxa (Pouech et al., 2006; Mazin and Pouech, 2008; Mazin et al., 2006, 2008). Isle of Wight, Great Britain; Wessex Formation, Wealden (Hauterivian-Barremian). Cranial and postcrania of Goniopholis crassidens (Owen, 1842; Hooley, 1907), teeth of Pholidosaurus sp. (Owen, 1842), teeth of Bernissartia sp. (Buffetaut and Ford, 1979), and a single skull of Theriosuchus sp. (Buffetaut, 1983). Galve/Teruel, Spain; El Castellar Formation and Camarillas Formation (Hauterivian-Barremian). Skull and teeth of Bernissartia sp. (Buscalioni et al., 1984), teeth and bones of Theriosuchus sp. (Buscalioni and Sanz, 1987b), and skeletal elements of Goniopholis (Buscalioni and Sanz, 1987a,b; Sa´nchez-Herna´ndez et al., 2007). ˜ a/Cuenca, Spain; Un ˜ a-Formation (Barremian). Partial skelUn etons of Unasuchus reginae and Theriosuchus ibericus, isolated skeletal elements of Goniopholis sp. and Bernissartia sp. (Brinkmann, 1989, 1992), dentary of Lisboasaurus (Schwarz and Fechner, 2008). ˜ a-Formation (Barremian). Teeth Pio Pajaro´n,Cuenca, Spain; Un of Theriosuchus ibericus and Bernissartia sp. (Winkler, 1995). Buenache de la Sierra, Spain; La Hue´rguina Limestone Formation (Upper Barremian). Isolated teeth of cf. Goniopholis gracilidens, Theriosuchus sp., Bernissartidae indet., and Crocodylomorpha indet. (Buscalioni et al., 2008). Vallipo´n and La Cantalera, Teruel, Spain; Artoles Member (Barremian-Aptian). Isolated remains of Goniopholis sp., Bernissartia ˜ aca and Canudo, 2001). sp., and Theriosuchus sp. (Ruiz-Omen
(13) Bernissart, Belgium; Sainte-Barbe clays, Wealden (BarremianAptian). Complete skeletons of Goniopholis sp. and Bernissartia fagesii (Dollo, 1883; Buffetaut, 1975; Salisbury et al., 1999). Geographically, the Scandinavian localities represent the easternmost and northernmost distribution of typical continental Jurassic-Cretaceous crocodyliform communities in Europe (Fig. 6). During the Late Jurassic and Early Cretaceous, most parts of Europe were covered by shallow epicontinental seas (Ziegler, 1990; Smith et al., 1994). Continental islands existed, such as the Iberian Meseta, and the localities listed above were placed along their margins. Whereas the general south-to-north distribution and position of these localities (Fig. 6) was not different during the Cretaceous thank it is today, the whole area was situated farther to the south, stretching between a latitude of 30 at the southernmost Spanish locality Buenache de la Sierra and of 45 at the northernmost locality in SkĂĽne (Smith et al., 1994, and: http://jan.ucc.nau.edu/~rcb7/nat. html). The common crocodyliform genera Goniopholis and Theriosuchus have been documented partly by bone material, but also by frequent ďŹ ndings of isolated teeth, and their occurrence in an area slightly more north- and eastward than hitherto known is not surprising. In contrast, Bernissartia is a rarer element, and its occurrence on Bornholm extends the geographical range of this taxon considerably. The Berriasian age of the Bornholm and SkĂĽne localities demonstrates that already in the earliest Cretaceous, this kind of crocodyliform assemblage was far distributed, corresponding to the coastal margins of the islands (Smith et al., 1994). Additionally to these more common taxa, some of the localities listed above have yielded evidence of very rare, or even endemic taxa: Lisboasaurus,
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Lusitanisuchus, and Unasuchus as well as a mixture of phylogenetically divergent taxa (Buscalioni and Vullo, 2008). All of these localities are contrasted by the Late Jurassic ‘‘Plattenkalk’’ localities Cerin/ France (Lortet, 1892) and Solnhofen in Germany (Wellnhofer, 1971), and the Berriasian ‘‘Plattenkalk’’ locality El Montsec in Spain (Buscalioni and Sanz, 1990a), which yield crocodyliform assemblages with exclusively small atoposaurid taxa, and in the case of Cerin, the relatively small mesoeucrocodylian Crocodileimus. A shift in the crocodyliform faunas at the end of the Early Cretaceous caused replacement of these faunal assemblages of non-neosuchian mesoeucrocodylians by eusuchian-ziphosuchian faunas (Buscalioni and Vullo, 2008).
Acknowledgements The fieldwork was carried out on a number of occasions with financial support from Lund Geological Field Club, the Royal Swedish Academy of Sciences, the Natural History Museum in Copenhagen, and Nordisk Forskerutdanningsakademi (NorFa). We thank Mikael Siverson and Regitze Benthien for assistance in the field and for donating important specimens. DSW thanks Gabriele Drescher for her assistance with the SEM photographs, Henrik Sto¨hr for his assistance with the multi-focus camera, and Oliver Wings for discussion of the palaeogeographic situation. JR and JL acknowledge the Swedish Research Council (Vetenskapsrådet) for funding their research. We thank Steven Salisbury and an anonymous Cretaceous Research reviewer for their helpful comments.
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