FOSSILS - A Guide to Prehistoric Life - (A Golden Nature Guide) by Ana C. Ponticelli

GOLDEN NATURE GUIDES Bl RD S

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/ 481 ILLUSTRATIONS IN COLOR

OSSILS A GUIDE TO PREHISTORIC LIFE by FRANK H. T. RHODES Professor of Geology, University College of Swansea, Wales

HERBERT S. ZIM PAUL R. SHAFFER

ILLUSTRATED BY RAYMOND PERLMAN Professor of Art, University of Illinois

NA.NI A GOLDEN NATURE GUIDE

GOLDEN PRESS

�) NEW

YORK

FO R E W O R D

This g u i d e to l ife of the past d iffers from oth e r G o l den Natu re G u i des. In stead of d ea l i n g w ith a s i n g l e g ro u p of p l ants or a n i ma l s , it d ea l s w ith them all. In stead of b e i n g c o n ce r n ed o n ly w ith t h e i m med iate p rese nt, i t s scope covers over half a b i l l ion years. In stead of d ea l i n g w ith l ife first h a n d , t h i s g u i de m ust rely on o n l y scant c l u es b its of s h e l l , b o n e, or s u n d ry fos s i l i m p ress i o n s . S u c h c l u es a re scarce, so each m u st b e stu d ied m i n utely. De ta i l s a re i m porta nt and th ey h ave been stres sed i n the systematic s u rvey of fos s i l fo rms. M ost fos s i l s have o n l y scientific n a m es a n d these often refer t o g ro u ps rather than to species. We h ave many i n stitut i o n s and i n d i v i d u a l s to t h a n k for aid w ith th i s book. D i o ramas and m u ra l s of the C h i cago N at. H i st. M u se u m are the basis for many of o u r resto ra t i o n s. T h e Un i ve rsity of Il l i n o i s , the Il l i n o i s G e o l o g ical S u rvey, the U.S. N at i o n a l M u seu m , the Un ivers ity C o l lege of Swa n sea, the Ward 's Natu ral H i sto ry Esta b l i s h m ent, Inc. l o a n ed us spec i m e n s . So d i d M . W. Sanderso n , A . F. Hag ner, W. W. Hay and F. J. Koen i g . A n gela H eath and S h i rley O s b o r n e have assisted the s e n i o r author, and many m o re of our co l l eag ues have g iven u s p h otog rap h s , s peci mens, c o m m e nts, a n d s u g g esti o n s . F . H .T.R. H . S .Z. P . R.S . ©Copyright 1962 by Western Publishing Company, Inc. All rights reserved, including rights of reproduction and use in any form or by any means, in cluding the making of copies by any photo process, or by any electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowledge retrieval system or device, unless permission in writing is obtained from the copyright proprietor. Pro duced in the U.S.A. by Western Publishing Company, Inc. Published by Golden Press, New York, N.Y. library of Congress Catalog Card Number: 62-21640

CONTENTS LIFE, PAST AND PRESENT..

T h e eart h , its l ife and how l i v i n g t h i n g s h a v e evolved. INTRODUCTION TO FOSSILS 10

W hat foss i l s are. How they are formed. D ifferent types of fossi l s . FOSSILS F O R AMATEURS . . .

Eq u i p ment needed. W h ere, when and how to c o l l ect. M u seums and other exh ibits. LIFE O F THE PAST......

A s u rvey of l ife era by era. Paleozoic E ra . . . . . . . . . .. . Mesozoic Era . . . Cenozoic Era . . . . . . . . . . . . .

34 49 61

IN VERTEBRATE FOSSILS . . .

A systematic s u rvey of g ro u p s . P rotozoa n s . . . . . . . . . . . S p o n g es . . . . . . . . . . . . . . Coele nte rates ; cora l s . . B ryozoans . . . . . . . . . . . . Brac h iopods . . . . . . . . .. A n n e l i d s ; worms . . . . . . A rthropod s ; tril obites . E c h i noderms . . . . . . . . . . M o l l u s ks . . . . . . . . . . . . G raptol ites . . . . . . . . . . .

typical ... ... . . . . .

. . . . .

...

75 76 77 81 82 92 93 1 04 110 1 31

VERTEBRATE FOSSILS . . . . . . 132

A look at some c o m m o n g r o u p s . F i s h . . . . . . . . . . . . . . . . . . . . . 1 32 A m p h ibia . . . . . . . . . . . . . . . . 1 39 Reptiles . . . . . . . . . . . . • . . . . 1 41 B i rd s . . . . . . . . . . . . . . . . . . . . 1 46 Mammals . . . . . . . • . . . . . . . . 1 47 PLANTS . . . . . . . . . . . . . . . . . . .

. . . . 150 A brief s u rvey of some c o m m o n fo ssil p la nts, their evo l ution and th e i r i d entificati o n .

INDEX . . . . .

. .

.............

. .

. . . 157

LIFE, PAST AND PRESENT T h e earth teems with l ife. M o u nta i n s , p rai ries, deserts, beach es, l a kes, rivers and seas - every part of l a n d , sea and air is i n ha b ited by l i v i n g t h i n g s . The n u m b er of d ifferent s p e c i es of l i v i n g t h i n g s i s e n o rm o u s . M o re than 350,000 s pe足 cies of p l a n ts and 1, 120,000 species of a n i ma l s are kn own . H ow d i d th ese m a n y species o ri g i nate? Has l ife always been the same as it i s n ow? Men h ave asked th ese q u es足 t i o n s fo r t h o u sa n d s of years. To a n swe r them we m u st tu rn to foss i l s a n d to a knowledge of l i v i n g o rg a n i s m s a n d t h e i r structu re. O n ly a n u n de rsta n d i n g o f l i vi n g an i ma l s c a n p ut l ife i n the frag m e nts o f b o n es a n d s he l l s m i l l i o n s of yea rs o l d . T h e e l e p hant i s t h e larg est l i v i n g l a n d a n i m a l . B u t the stu dy of fo s s i l s s h ows not o n l y that e l e p hants a re a recent g ro u p in the l o n g h i sto ry of l iv i n g th i n gs but a l s o that early e l e p h ants l o o ked m o re l i ke hogs. As g eo l o g i sts t race e l e p h ant fos s i l s from o l d e r to you n g e r rocks t h ey p i ece tog ether the h i sto ry of e l e p h ant evo l ut i o n . Fo ss i l b o n es a n d teeth reveal the stru ct u re of early e l e p h a nts, but by stu d y i n g t h ese fo s s i l s i n the l i g ht of the a nato my of l i vi ng e l e p h ants, com p lete recon structio n s of exti n ct e l e p h ants can be made w ith reaso n a b l e acc u racy. S o m e u n u s ua l occ u r rences of m astodon fos s i l s w ith c r u d e fl i nt wea p o n s p rove that t h e s e e l e p h ants were h u nted b y o u r a n cestors. 4

EVOLUT I O N O F E LE P H A N T S

T R I LO P H O D O N U . M iocene-L. P l iocene 1 0-20 m i l l i o n years ago

L i v i n g ele p h a nts are s u rvivors of a n an足 cient, m o re w i d e s p read and varied gro u p , w h i c h evolved f r o m p i g - s ized ancestors of the Upper Eocene. (See the g e o l o g ic clock, p p . 30-31 .) O n l y a few of the m a n y ext i nct elephants and their kin a r e s h own.

OVER 1,000,000 ANIMAL SPECIES

1. 2. 3. ·�·...--... 4 . 5. 6.

A rth ropods-900 ,000 M o l l u sks-45,000 C h o rdates-45,000 P rotozo a n s - 30,000 Worm- l i ke p h y l a - 38,000 Other i n v e rteb rates - 2 1 ,000 A pproxi mately 1 ,000,000

A L L FO R M S OF L I FE have evo l ved from early beg i n n i n g s, s o m e th ree b i l l io n yea rs ago. F r o m rel atively few p ri m itive forms, the maj o r g ro u ps of p l ants a n d a n i m a l s deve l o p e d . L i v i n g th i n g s b e c a m e m o re c o m p l i cated a n d ada pted t o many d i ffe rent ways of l i v i n g . T h e n u m be r of d ifferent s pe c i es g rad u a l ly i n creased u nt i l t h ey rea c h ed the trem e n d o u s d i vers ity of today. The stu d y of fos s i l s (paleonto l o g y) t races the vari o u s paths by w h i c h a n i mals and p lants evo l ved to t h e i r present fo rms. S o m e , l i ke e l e p ha nts a n d h o rses, have c h a n ged g reatly ·th ro u gh the ages. Oth e rs, l i ke the h o rsesh oe c rab a n d cockroach, have not c h a n g ed i n h u n d reds of m i l l i o n s of yea rs . Sti l l ot h e r foss i l s s h ow l i n es o f develo pment that c a m e to a d ead e n d . G ia nt S l oth s, o n ce p l entif u l , are k n o w n o n l y as fos s i l s . GL YPTODONT, 9ft., an armo red mam

mal from the late Cenozoic, is a fossil that s h ows spectac u l a r and obvious ada ptat i o n . T h i s relative of the armadillos was protected a g a i n st carnivores and other e n e m i es by a th i c k , solid, d o m ed armor, w h i c h reached 5 ft. in len gth i n s o m e forms. T he h ead a n d ta i l were a l so armored, and in some species the tail te r m i nated i n a s p i ked, mace- l i ke c l u b . Yet despite, o r because o f , t h e s e u n u sual adaptions g l y ptodo nts became exti n ct.

ABOUT 350,000 PLANT SPECIES

1. 2. 3. 4.

Floweri n g P lan ts-250,000 Ferns, C o n ifers, etc. -10 ,000 M o s ses and Liverwo rts-23,000 A l gae, F u n g i , etc.-60,000 A bo u t 350,000 plant species

M o st p l ants a n d a n i m a l s ex i st o n l y be cause t h ey a re s u ccessfu l l y adapted to t h e i r e n v i ro n m ent s. Eac h d i sti n ct e n v i ro n ment s u c h as a desert, pond o r m o u n ta i n t o p s u p p o rts a m o re o r less d i sti n ct p o p u lati o n o f a n i m a l s a n d p l a nts. T h ose w h i c h , over l o n g p e r i o d s of t i m e , h a v e beco m e fitted t o c o p e w i t h local c o n d it i o n s h a v e s u r v i v e d . A l l t h e rest have become exti n ct. M a n y l i v i n g th i n g s a re u n i q u e l y adapted to parti c u l a r e n v i ro n m e nts. T h e strea m l i n e d s hape of a fis h a n d the struct u re a n d f u n ct i o n o f its fi n s a n d ta i l a re adaptat i o n s t o l ife i n t h e water. T h e fl e s h y ste m s o f a cact u s are adaptat i o n s that c o n serve water i n t h e desert. Such ada ptati o n s s u cceeded, b u t the fo s s i l record i s strew n with the rem a i n s of those t h at fa i l e d . T h e s l o g a n o f l ife m a y wel l be - a d a pt o r per i s h . A D A PT A T I O N

S u rvival i n a n i m a l s depends o n a d a pta t i o n s as varied and as i ntri cate as t h e a n i m a l s t h e msel ves. V i rt u a l l y every struc t u re of a plant o r a n i ma l may be regarded as a d a ptive. M a n y a n i ma l s have p rotec tive c o l o r i n g and a few forms, s u c h as the bottom-l i v i n g flo u n der, a re a b l e to c h a n ge t h e i r color t o c o n f o r m to their back g ro u n d . S u c h an i ntri cate adaptat i o n is rarely d i s cern i b l e in foss i l s. However, if the adaptati on affects b o ne or s h e l l , it may s h ow u p c l early i n the foss i l record.

EVOLUTION OF TH VERTEBRATES

A dapted from W. K. Gregory

ENT OF M O D E R N A N I M A L L I FE is d if足 fi c u lt to trace b ecause the fos s i l reco rd is i n c o m p l ete. E n o u g h i s known to s u g g est the g e n e ral pattern of evo l u 足 t i o n a n d t o reco n struct i n some d etai l h i story of g ro u p s i n 8

o o\"

\)IS sa

a <os 1'\e

\l's

PLACENTALS

those a reas w h ere foss i l s occ u r a b u n d a n t l y. T h e c h a rt s h ows relat i o n s h i ps a m o n g maj o r g ro u ps of v e rte b rates. Those a n i ma l s w i th i n a g i ven color p roba b ly d ev e l o ped from co m m on a n cesto rs. 9

INTRODUCTION TO FOSSILS Fossils are the remains of prehistoric life or some other direct evidence that such life existed. To become fossil足 ized a plant or animal must usually have hard parts, such as bone, shell, or wood.lt must be buried quickly to prevent decay and must be undisturbed throughout the long proc足 ess. Because of all this very few plants or animals that die are preserved as fossils. In rare cases whole animals may be preserved. In Siberia and Alaska fossil mammoths have been found in the frozen ground, completely refrigerated for some 25,000 years. In Galicia (Poland) an Ice Age Woolly Rhinoceros was well preserved in asphalt. In semi-arid South America, parts of mummified Ground Sloths have been preserved in caves. In each of these cases an unusual condition足 cold, chemical action and dryness-was involved.

Carbon ized leaf

I n sect p reserved in amber

SO FT P A RTS are rarely found intact but insects' exo足 skeletons and minute appendages have been preserved in amber, the hardened resin of ancient trees. Leaves and small, soft marine animals buried in mud which hardened into shale have sometimes left behind a thin film of carbon outlining their form and preserving delicate details of their structure. And, in western Canada, sandstone casts of dinosaur skins have been preserved.

HA R D P A RTS are often preserved with little or no alteration. Teeth of sharks and mammals are examples, and small jaws of ancient sea worms have been found. Bones may be preserved but more often have been altered and replaced by dissolved mineral matter. Shells fre足 quently remain intact and in a few places logs and stumps have been preserved in peat or coal. Foss i l b rach iopod w ith orig i n a l pearly l u st e r

J aw of marine w o r m

Cross sect ion of petr ified wood

A LTER A T I O N of hard parts preserved as fossils is common.

Circulating water dissolves chemicals from

shells and bones and leaves them light and spongy. More often as chemicals are dissolved they are replaced by others. Silica, lime and iron compounds are commonly deposited in fossils. Sometimes this replacement pre足 serves the original structure of the plant or animal com足 pletely. In some petrified wood, silica has replaced the original woody structure so perfectly that the cells and annual rings show clearly. In most petrified wood and most replacement fossils, the replacement is less perfect and shows only the general form. Brach iopod she l l replaced by d o l o m ite

2. Sand h a rdens to rock. S h e l l i nte rior u n ti l l ed.

3. S h e l l m at e r i a l d i s s o l ved. Cav ity wal l is m o ld of s h e l l .

4. D i s so l ved c h e m icals till mold to form cast.

5. Both m o ld and cast are foss i ls, rep l i cas of the o r i g i n a l s u rface.

M O L D S A N D C A STS

Not all fossils are bones, shells

and other remains. Some are mere indications of pre足 historic life. All the original plant or animal material may be dissolved away so that only a cavity remains-the walls of which are a natural mold of the fossil. Later, dissolved substances may fill the cavity, forming a natural cast of the original. Such casts are common fossil forms. Foot足 prints or trails of animals may harden as a mold. Filled with fresh mud, casts are formed and both may be pre足 served, as in the red sandstone (Triassic) of the Con足 necticut Valley which contains tracks of dinosaurs.

OTHER TY PES OF FOSSI LS include some curious forms, all of which are evidence of ancient life.

B O R I N G S of worms and mol m o l l us k borings

lusks indicate that these animals lived millions of years ago. Such fossils are common. Sometimes petrified wood shows borings also.

G A STR O L I THS rounded

pebbles

are

smooth,

found

rib

cages of dinosaurs. These stones probably aided the din osaurs' di gestion just as gravel in their giz zards helps chickens crush grain. Polished dinosaur gastroliths

gastroliths

are

found

on ly in "dinosaur country."

C O P R O L I TES are fossil excreta and give a clue to the diet of an cient animals.These lumpy fossils are usually associated with land animals of the past 50 million years. co prolite

A RTIFA CTS are stone tools or weapons made by ancient man. Found in many parts of the world, the oldest have been found with bones of animals n ow extinct. The

A urignacian han d axe

first stone artifacts were crude and difficult to recognize. More recent ones were chipped and polished to make beautiful im

N eo lithic s craper

plements.

S E D I M E N T A RY RO CKS con tai n nearly all the fos s i l s that are fo u n d . T h ese rocks are formed of sediments - m u d , s a n d , c lay-:-d e pos ited m e c h a n i ca l ly, c h e m i c a l l y or by o rga n i s m s , i n seas, lakes, caves, deserts a n d river va l leys.

G r a n d C a n y o n strata

STRATA o r layers a re a c h a rac

teristic of sed i m e ntary rocks. T h e botto m layers a re n at u ra l l y t h e o l d est. But n ot a l l sed i ments are eve n l y or c l early bedded . l i mesto n e

m a i n ly cal c i u m carb o n ate, c o m m o n i n warm, s h a l l ow s e a s , often has foss i l s. L I M E STO N E ,

S H A L E i s a fi n e-g ra i ned rock formed from s i lt and c lays. It p re serves foss i l s wel l . - � -�;

S A N DST O N E i s w i d e s p read i n

desert d e p o s its a n d i n s h a l l ow water s e d i m e nts. R I P P L E M A RKS A N D M U D C R A CKS c h a racterize many sed i m e ntary rocks formed i n shal low wate rs . R i p p l e m arks are com mon i n s ha l e . M u d c racks may form as m u d and c l ays d ry. T h ese i m p l y the p resence of s u n l i g ht, water and m o d e rate te m pe ratu res - co n d it i o n s related to the possi b i l ities of l ife.

' �

'-_

. .,

. -y -::: sandsto n e

!-�� ' �.

N o rth American sed ime nta ry formati o n s deposited d u r i n g the past 600 m i l l ion years. Small l o ca l beds of sed i m entary rock a re also found w ith in a reas of i g neous a n d m etamo r p h i c rock.

S E D I M E N TA RY ROCKS, often r i c h in fos s i l s, occ u r o v e r m u c h o f N o rth A m e r i ca. B u t i n ma n y p l aces t h e s o l i d roc ks a re cove red with so i l o r g l acia l d ep o s i ts , o r the fos s i l -beari ng layers lie deep ben eath oth e r rocks. H e n ce fos s i l h u nt i n g i s restri cted to outcrop s -p laces w h e re the sed i me nta ry rock i s exposed at the s u rface, as in c l iffs, river banks, road c uts o r q u a rri es. The fact that foss i l s a re fo u n d in sed i menta ry ro cks is n o co i n c i d e n ce. Oth e r rocks are su bjected to forces or c o n d i t i o n s w h i c h d estroy foss i l s ea s i l y. The p rocesses

Foss i l b o n y fi s h from Eocene G reen River formati o n , Wyom i n g .

that wear d o w n the eart h ' s s u rface prod uce the sed i m e nts from w h i c h s ed i m entary roc ks a re formed. T hese wea r i n g d own p roces ses (deg radat i o n) i n vo l ve ra i nfal l , evap o ra足 t i o n , w i n d , ru n n ing water a n d tra n s p o rtati o n a m o n g other th i n g s . And t h e fo s s i l fi s h p i ctu red a bove n ot o n l y p ro ves that fi s h es l i ved in t h e d i stant past, b ut that c o n d it i o n s i n the lake in w hich it lived were not g reat ly different fro m those i n many a reas today. T h i s a n d o l d e r foss i l s p rovide evid e n c e that basic p h ys i cal c o n diti o n s maki n g l ife poss i b l e today existed n ot o n ly 50 m i l l io n years ago w h e n th i s fi s h beca m e a fo s s i l b u t probably go back a b o ut two a n d a half b i l l i on years. Every foss i l , even the m ost c o m m o n, te l l s a fasc i nati n g sto ry of the c h a n g i n g s u rface of the ea rth and the deve l o p ment of l ife u po n it. 17

co ncret i o n

d o l o m ite "pse ud o-coral"

septar ian n o d u l e

Pseud ofossils, often shaped l i ke fossi ls, lack d etai l ed fossi l str u ctures.

PSEU D O FOSSI LS are rock str.uctures that resemble fossils. They may have any shape and often look like parts of plants or animals. A geologist will usually recog足 nize a pseudofossil at once, but an amateur may be misled. Pseudofossils resemble fossils only in external form. They never have the detailed structure of true fossils. They may occur in improbable situations, as for instance a "footprint" in rock formed long before any creatures walked on land. Pseudofossils are formed in many ways.

Some are

water-worn fragments of rock. Concretions which form in sedimentary rock may contain a fossil, though most do not. Concretions, harder than the rock in which they occur, are often found on the surface. Some minerals form den足 drites or fernlike deposits on or in rocks. Moss agates are dendrites, not fossil moss. pyro l usite den drites on d o l o m ite

po l ished moss a gate

THE RAREST FOSSILS are those of h u man bei n g s. This jaw bone u n earthed in Africa i n 1 961

p u shed the o ri g i n of h u ma n s o r near- h u m a n , tool- u s i ng a n i ma l s b a c k to n e a r l y 1 , 750,000 years a g o .

FOSSILS FOR AMATEURS Collecting and studying fossils can be an interesting hobby as well as an important science. Only during the past two centuries has paleontology, the study of fossils, moved to the professional level. Amateurs have collected and studied fossils much longer and today they enjoy field trips and collecting as much as ever. Major dis coveries have been made by amateurs and many have won acclaim from professional geologists. Unless the ground is covered with snow, collecting fossils is an all-year occupation. It takes you out-of-doors and off the beaten track. You learn to know your region intimately and enjoy the company of other local "rock hounds. " No other hobby can open such w ide vistas of time and space. The study of fossils still has many un solved problems which a serious amateur can tackle with some chance of personal success. Such a person will understand fossils better if he also keeps up a con t inued interest in living animals and plants.

FOSSILS RECONSTRUCT LIFE

FOSSILS PLOT GEOGRAPHY

They enable scienti sts to p i ct u re accu rate ly many ki nds of l o n g exti n ct p lants and a n i m a l s .

They i n d i cate ancient land and water a reas and show the c h a n g i n g conti nents.

WHY C O L L ECT FO S S I LS? M ost peo p l e c o l l ect for the s i m p l e fu n of it -for the fun of tram p i n g and ex p l o ri n g ; for the excitement of a rare fi n d ; for t h e c h a l l enge of "work i n g o ut" a p e rfect s p ec i m e n . But i n t h e c o u rse of d o i n g a l l t h i s , the layers o f sed i m enta ry rocks u nfold l i ke pages of a g ig antic book, revea l i n g the fas c i nat i n g sto ry ·of the eart h ' s l o n g and exciti n g past. Events 50, 1 00 o r 500 m ' i l l i o n years a g o become real beca u s e t h e fos s i l s y o u h ave fo u n d p rov i d e a clear co n n ecti o n with byg o n e ages. With the a i d of fos s i l s the reco n structi o n of p re h i sto r i c p l a nts a n d a n i ma l s w a s po s s i b l e , a n d t h e .story of the evo l ut i o n of l ife became c l ea r . With o ut t h e evi d e n ce of foss i l s , evo l ut i o n wo u l d sti l l be a t heory , n ot a fact. Foss i l s h e l p deter m i n e w h ether sed i m ents were formed i n s h a l l ow o r d e e p s e a s , i n r i v e r s , i n swa m p s o r i n deserts. T h u s they g ive a c l ue tb t h e geog ra p h y a n d eco l o gy o f t h e past and s h ow h ow the conti n ents a n d seas h ave c h a n g ed . Fo s s i l s p rove that A laska was o n ce co n n ected w ith S i beria a n d A u stralia with Malaya . The d i st r i b ution of s h a l low water m o l l u s ks a i d s in trac i n g a n c i ent s h o re l ine s . 20

petro l e u m

building stones

FOSSILS

HELP

CORRELATE

STRATA I n dex fo s s i l s esta b l i s h

the t i m e relati o n s h i p between rocks of d i fferent a reas.

d iatom s fo r fi l ters

FOSSILS ARE NATURAL RE足 SOURCES

Fossi l s a re a s o u rce of c oal , o i l , l i m e , p h o s p hate a n d b u i l d i n g stones.

Fos s i l s , in a d d it i on to b e i n g clues to a n c i e n t g e o g ra p h y , a re a l so c l u e s to the c l i m ate o f t h e past. Fo s s i l c o ra l s s h ow t h at warm, s h a l l ow s eas o n ce covered N ew Y o r k . A n d p l a nt foss i l s s h ow t h at the c l i mates of A nta rct i ca and G reen l a n d w e re o n ce m i l d . C e rta i n fos s i l s of l i m ited t i m e d i stri b u t i o n c l ea r l y m a r k certa i n b e d s o r st rata of r o c k s . T h es e are i n dex foss i l s a n d t h e i r o c c u rre n c e i n rocks l ocated m i l e s a p a rt p roves these rocks w e re formed at the same ti m e . T h i s u se of fos s i l s to c o rrelate strata is i m po rtant in m a p p i n g ro c k formati o n s a n d i n l o cati n g v a l u a b l e m i n e ra l d e p o s its. Foss i l s t h e m se l v e s o r rocks l o cated b y fos s i l s p ro v i d e n at u ra l res o u rces val u ed a t b i l l i o n s of d o l l ar s. N ea r l y a l l o u r f u e l s a re foss i l f u e l s . C o a l a n d o i l a re t h e rem a i n s o f a n c i ent p l a nts a n d a n i ma l s . Fo s s i l l i mesto n e s m a ke ex足 c e l l e nt b u i l d i n g sto n e s . Some are cut for o r n a m e ntal u se . M i c ro-fo s s i l s a re used as fi lte rs, fi l lers, i n p o l i s h es a n d f o r m a n y oth e r p u rposes. S o m e p h o s p h ate b e d s a re asso足 c i ated w ith l a rg e d e p o s its of fos s i l b o n es. A m be r a n d j et are fos s i l s u sed as j ewel ry. 21

Rockh o u n d s i n a quarry

STU D Y I N G FOSSI LS is s o m eth i n g l i ke m a k i n g a rab

bit stew-yo u fi rst m u st get a ra b b it. Co n s i d e r i n g t h e earth a s a w h o l e , foss i l s a r e rare. Many a r e b u ried b e n eath t h e s e a . Fo rests, g rass l a n d s , swa m p s , deserts, s o i l a n d r o c k d e b r i s c o v e r many m o re . Yet d e s p ite a l l t h i s , foss i l s a re often easy t o find . WHERE TO LOOK for foss i l s is eas i l y sett l e d . Look i n sed i m enta ry rocks, fo r these a re the p r i n c i p l e rocks w h i c h may conta i n fo s s i l s . Occas i o n a l l y fossils a re fo u n d i n b e d s o f v o l ca n i c a s h o r are even p reserved i n lava, b u t t h e s e are rare. Sed i m e ntary rocks (mai n l y s a n d sto n e , s h a l e and l i m eston e) a r e com mon, b ut n o t a l l o f th e m conta i n foss i l s . Maps i n t h i s b o o k s h ow w h e re s u c h sed i m ents a re exposed b ut t h i s rou g h data m u st be s u p p l e mented by d etai l ed maps and state g e o l o g i cal p u b licat i o n s (see p . 25) . I n g e n e ra l , fresh expos u res of rock a re best for c o l l ect ing . Look in road o r ra i l road cuts. Visit m i n e d u m p s, quar ries and p l aces w h e re rock i s b e i n g excavated fo r n ew constructi o n . Cl iffs, river banks, h ead l a n d s a n d oth e r natu ral e x p o s u res a r e good p l aces al so. R e m e m ber that a l l t h ese p l aces . i n volve a certa i n e l e m e nt of d a n g e r. Watc h for t raffic at roadc uts and get perm i s s i o n before enteri n g quarries. Loose rocks can b e a da n g er t o y o u a n d t o any one b e l ow you . 22

TOOLS for col l ecti n g foss i l s a re s i m i la r to those used

by any rockh o u n d . A geolog i st's , p l aste rer's o r b r i c k足 layer's h a m m e r is esse ntia l . So i s a knapsack or sto ut s h o u l d e r bag fo r carry i n g spec i m e n s . Foss i l s a re often d e l i cate. Take n ews paper a n d w rap each s p e c i m e n sepa足 rately as soon as it is c o l l ected . Put a label o r s l i p of paper with each s pec imen g i v i n g l o cati o n , fo rmati o n , d ate, and i d entificat i o n if k n ow n . A large a n d a s m a l l c o l d c h isel a re n eeded t o re move spec i me n s , for h a m m e ri n g alone i s ra rely e n o u g h . A s m a l l shovel a n d a steel w recki n g bar m ay a l s o p rove handy. You w i l l often need road maps and m o re d eta i l ed to pog ra p h i c o r g e o l o g i ca l maps to l ocate y o u r o utc ro p s . A mag n ify i n g g lass o r h a n d l e n s (5 t o 1 0 power) i s worth hav i n g . Ca rry a com pass, a fi rst-ai d kit a n d a pocket kn ife. You may need to carry yo u r own food and water too.

H OW TO C O L LECT Take t i m e to s u rvey the a rea. Look fo r rock s u rfaces where weathering has exposed fos s i l s . Weathered-out s p e c i m ens a re easy t o c o l l ect a n d m a y b e i n excel l ent c o n d it i o n . T u rn o v e r rock frag me nts a n d stu d y a l l s i d e s . B reak o p e n concreti o n s if t h e y o cc u r. S h o u l d you locate verteb rate b o n es or a n y foss i l you be l i eve rare, l eave it i n tact a n d g et profes s i o n a l h e l p . Va l u a b l e foss i l s h ave been r u i ned by b u n g led atte m pts to rem ove th em. P R E P A RA T I O N A N D CLE A N I N G s h o u l d be d o n e at h o m e afte r s p ec i m e n s have been removed . The d e l i cate task of c l ea n i n g and work i n g out a s pe c i m e n is best d o n e o n a sto ut tab l e w i t h good l i g ht a n d adequate too l s . O l d d enta l too l s a r e excel lent for th i s p u rpose. Electric-pow ered "h o b by sets" often conta i n s m a l l d r i l l s a n d g ri n d e rs w h i c h make the tas k easy. Bone a n d other d e l i cate foss i l s may req u i re a coati ng o f a p reservative s u c h a s s h e l lac o r Alvar to p revent c racki n g a n d deteri o ratio n . I D E N T I FI CA T I O N A N D EXH I B I T I O N o f y o u r c o l lection b ring y o u r w o r k t o a c l i max. Reg i onal vol u mes on fos s i l s s h o u l d be c o n s u lted for identificat i o n . Sec u re the aid of g e o l o g i sts at u n ivers ities a n d m u s e u m s . T h ese experts are u s u a l ly g lad to aid an a m ateu r. S p ot y o u r specimen with a d ro p o f q u ic k-d ry i n g enamel a n d p ut yo u r catalog n u m be r in I n d i a i n k on the s pot. Reco rd t h i s n u m b e r a n d the name, l ocation a n d oth e r d ata o n a card a n d a l so i n a separate cata l og . Foss i l s can be stored i n cardboard t rays of vary i n g sizes p u rchased f r o m scientific s u p p l y h o u ses. P u t yo u r label i n the tray b e n eath the spec i m e n . Keep s m a l l speci m e n s i n v i a l s . B u i l d ex h i b it cases o r a b a n k of shal low d rawers to h o l d trays and specime n s . 24

M A P S A R E I M PORTA N T beca use so m u c h info rma tio n is p rese nted in them about sed i m enta ry formatio n s, structu res a n d strata. With out maps the locatio n of fossil deposits is i m possib le; use all kin d s . Road maps: Obtain sets o f several kinds c overing your area. K e e p them u p

t o date. Mark small back roads that may n o t ap pear on the maps. K e e p one set at home for refe ren ce. Take an other set into the field with you. Topographic maps are produced by the U.S. Geological S u rvey. These are more detailed than road maps and show the la nd and water feat u res as well as c u lture (roads, b ridg es, towns, h o u ses. etc.). An I n d ex Map for your state can be o btai ned from the U.S. Geolog1cal Su rvey. Washin gton 25. D.C. Geological maps: These are often prepared by state geological s u rveys either as a state g e o l o gical map or in relationship to specific repo rts. Check with your state s u rvey and get their list of p u b lications.

BOOKS wil l h e l p you identify fossils, u n dersta n d basic geology and the story of evo l utio n . C h eck the p u b l icatio n s a n d rep o rts o f y o u r state geol ogical s u rvey. Write the S u pt. of Doc., Was h . 25, D.C. for a l i st of U.S. G o vt. p u b l i catio n s i n geology. T h e fo l l owin g list o f textbooks a n d gen eral refe rences wil l a l so h e l p . Arnold, C . A., A N INT R O D U C TION T O PALEOBOTANY. M c G raw-Hill, New York, 1 947. Bac k g r o u n d information on fos sil pla nts. Colbe rt. E. H .. E V O L U TION OF THE VE RTEBRATES, John Woley. N ew York, 1 955. U sefu l for general reading. Crone•s and K r u m bein, DOWN TO EARTH, An Introd uction to G e ology. U n iv. of Chicago P ress. Chicago, 1 936. A readable, lavishly ill u strated acco u n t o f geology o n a c o l l e g e level. Fenton a n d Fenton. THE FOSSIL BOOK, D o u bleday, Garden City. N.Y.. 1 958. An tntrod uctio n to paleo ntology with fi n e illustrations. Matthews, W. H., FOSSILS. Ba rnes a n d No ble, New York, 1 962. Excellent su rvey and introdu ction to p rehistoric life. Moo re, La licker and Fischer, IN VERTEBRATE FOSSILS, M c G raw-Hill, New York, 1 952. U seful for fossil identification. Moo re, R. C., INT R O D U C TION TO HISTORICAL GEOLOGY, M c G raw-Hill, New York, 1 958. A good s o u rce for the g eologic history of North America. Rhodes, F. H. T., THE E V O L U TION OF LIFE, P e n g uin Books, Baltimore, Md., 1 962. A n ill u strated, reada b l e account of the history of l ife. S i m p son, P itte n d righ and Tiffany, LIFE: An Introd u ction to Bio l o g y. Harcou rt, Brace & Co., New York, 1 95 7. An i ntrod u ctory text on biology. C o m p rehen sive a n d excellent.

M U S E U M S A N D EXH I B I TS wi l l show you exce l lent spec i m e n s a n d i nt ro d u ce you to foss i l s that do not occ u r locally. M a n y u n ivers ities and m ost large c ities have m u seu m s w i t h foss i l c o l l ecti o n s . S o m e o utsta n d i n g ones a re l i sted below. Ala., U n ive rsity -A la. M u seum of

New York, A l bany - N.Y. State

N atu ral H i story Ariz., H o l b rook - Petr ified Fo rest N ati onal M o n ument M u seum Cal., Los A ngeles-L.A. Co. M u s. Colo., Denver-Mus. of N at. H i s!., Boulder-U. Colo. M u s. Conn., New Have n - Peabody M u s. of Nat. H i s!. (Yale U n iv.) D.C., Was h i n gton - S m ithso n ian I n s!., U.S. N ational M useum Fla., G a i n e s v i l l e -Fia. State M u s., U n ivers ity of Flo rida Ill., C h icag o -Chic. Nat. H i s!. M u s., S p r i n gfield -Ill. State M u s. Kansas, Law rence-U. of Kansas M us. of Nat u ra l H i sto ry Mass., C a m b ridge - M u s e u m of Co m parative Zoology Mich., Ann A r b o r -U n ivers ity of M ic h i ga n M u seum Neb., L i n co l n -U n iv. of Neb raska State M u se u m

Mus., Buffa l o -B u ffa l o M u s . of Sci., N.Y. C ity -Amer. M u seum of Nat u ral H istory Ohio, Cleveland - C l eveland M u s. of Nat u ra l H i story Pe n nsylva nia , P h i !ad e lph i a Acad. of N at. S c i . , P itts b u rg h C a r n e g i e I n s!. M u se u m So. Dakota, R a p i d C ity- M u s. o f So. Da ko"ta S c h o o l o f M i nes Texas, A u stin - Texas Memorial M useum Utah, J e n s e n -D i no s a u r Nat. Mon., Verna l -Utah Field H se. of Nat. H i s!. Wash., Va ntage- G i n kgo Petrified Fo rest State Park M u s e u m CANADA, Ottawa, O ntario- N at. M u se u m of Canada Toronto, O nta rio- Royal Ontario Museum Montreal, Que bec- Redpath M u seum

living (d iameter a b o u t 6 i n .)

LIFE OF THE PAST Fo s s i l s are a l m o st always i n c o m p l ete. A fos s i l h o rse i s known by a s k u l l a n d a few b o n es . O n ly t h e s h e l l o f a fos s i l s h e l lfi s h i s fo u n d , a n d a n a n c i ent tree i s rep rese n ted o n ly by leaf frag m e n ts . Yet e n t i re p l a nts a n d a n i ma l s are re足 c o n structed on a s c i e ntific basis that uses present l i v i n g fo rms as a key to i nterpret t h e l ife o f t h e past. A stu d y of l i v i n g p l a nts and a n i ma l s i s essential to u n d e rsta n d foss i l s . Fos s i l a m m o n ites h ave been exti n ct for 70 m i l l i o n years, b ut t h e i r s h e l l s a re v e ry s i m i l a r to t h e l i v i n g Pearly N a uti l u s . G e o l o g i sts ass u m e t h at t h e i r s oft parts were a l so s i m i la r a n d make reco n st r u cti o n s accord足 i n g ly. A co m pa r i s o n of large verteb rate foss i l s with l i v i n g species s h ows h o w m u sc l es fit t o b o n e s . T h i s i n d i cates body stru ctu re. Li v i n g p l a nts h e l p u s u n d e rsta n d t h o s e known o n l y by fo s s i l frag ments. T h ese reco n structi o n s , with oth e r g e o l o g i c i nfo rmati o n , make i t poss i b le t o fo rm a n accu rate p i ct u re of the a n i mal a n d its enviro n m e n t. T h i s i n t e r p l ay of past a n d p resent i l l u st rates how man u ses science to d ev el o p n ew fro ntie rs-an i n c reased u n d e rstan d i n g of both past and p resent at the same t i m e . 27

GRAND CANYON rock forma足 t i o ns a re shown in cross sect i o n ab ove, n u m be red i n o rder o f a ge.

The l o west n u m bers a re the o l dest. Over 1 . 5 b i l l i o n yea rs of earth h i story a re reco rded here.

G E O L OG I C T I M E is the fourth dimension of the earth's past. Without it, objects and events cannot be placed in their proper relationship. Only the almost incomprehen足 sible length of geologic time can explain the great changes in life and in the earth itself. The development of a reliable scale of geologic time is one of the great feats of the human mind. Early steps were taken by observing the occurrence of sedimentary rocks in horizontal layers and noting the rate at which sediments formed in bays and basins. The simple observation that younger layers formed on top of older ones became the first key to the long geologic time scale. Studies show that the earth includes a vast series of sedimentary rocks, most with characteristic fossils. Even when layers are tilted, folded and broken, or when erosion has left only discontinuous remnants of strata, fossils re足 veal their order and relationships.

T h e re are ways by w h i c h t h e age of a roc k or fos s i l can be m ea s u red d i rectly in years. One m ethod i s based on the b reakdown of rad ioactive e l e m ents. T h ese e l e m e nts have u n sta b l e ato m i c n u c l e i that b reak dow n at a steady, meas u ra b l e rate to form more sta b l e e l e m e nt s . T h u s, u ra n i u m b reaks dow n i n to lead a n d h e l i u m at a v e ry s low rate t h at is i n d e p e n d e nt of h eat, p re s s u re. or ot h e r con d i tion s . O n e g ra m of u ra n i u m for m s 1 /7,000 g ra m of l ead every m i l l ion years. So a c h em i st who can accu rately meas u re t h e ratio of u ra n i u m to l ead in a rock can g et a n accu rate m ea s u re o f t h e age o f that roc k. W h e n u ra n 1 u m m i n e ra l s occ u r i n roc ks assoc iated with fos s i l s, t h e a g e of t h e fos s i l s can b e i n ferre d . T h i s m ethod a n d ot h e rs l i ke it, u s i n g thori u m, ru b i d i u m, potas s i u m a n d carbon, requ i re the most accu rate c h e m i cal a n a lyses. But, as a resu lt, t h e g eolog i c t i m e scale is becom i n g more re l i a b l e, year by year. Ot h e r data i n vol v i n g m eteorites a n d t h e fo rmation of the solar syste m s u g g est t h e earth i s fou r to five b i l l ion years old. Foss i l s two and a half b i l l ion years o l d have been d i scovered, thoug h fos s i l s did not becom e ab u n d ant u nti l a bout 600 m i l l ion years ago. Geolog i sts know from t h e rate that sed i m ents form today that m u c h t i m e was n eeded to make a l l the sed i m e nta ry rocks that tota l ov er 75 m i l es i n t h i c k n e s s . URANIU M T O LEA D B RE A K D O W N T h i s s i m plified d i a g r a m s h ow s o n e p atlern by w h i c h u ra n i u m 238 c h a n g es to v a r i o u s i so t o p e s a n d fin a l l y to l e a d 206.

Rad i u m 226

Astati n e 2 1 8 Polon ium 210

Polon i u m 2 1 8

\ •

LEAD 206

Eve n t h i s t i m e esti m ate fa l l s s h o rt because there were l o n g p e r i o d s d u ri n g w h i c h sed i m ents were worn away. Yet d es p ite these d ifficu lties the study of u n a lte red , foss i l 足 bea r i n g sed i me nts s h ows that they fi t i nto th ree g reat e ras of t i m e. T h ese eras, i n t u r n , a re d ivided i nto 12 g eo l o g i c p e r i o d s w h i c h a l so have been d i v i ded arid red i v i ded u nt i l each fo rmation can be g iven a name a n d a p l ace i n the g eo l o g i c time scale. This reco rd g oes back a b o ut 600 m i l l i o n yea rs a n d p rovides a relative dat i n g for fos s i l s . Yet th i s t i m e s c a l e (see chart, p. 31) c a n be a n d i s u sed every day. We s p eak of a J u rass i c fo s s i l just as we s peak of a C o l o n i a l m a n s i o n and k now ro ug h ly w h e re b oth fit i nto h i story. Periods a re d i v i d ed a n d red iv i d ed when con足 d iti o n s p e r m it u nt i l each strata i s i d entifi e d .

T H E G EO LO G I C "C LOCK" The larger c i rc l e represents o n ly the last 600 m i l l ion years. Eac h ''h o u r'' rep re足 sents 50 m i l l i o n years.

T he smaller c i rcle represents the a g e o f t h e eart h , a b o u t 5 b i l l i o n years. Life has exi sted about half t hat t i m e a n d t h e s m a l l segment i s 6 00 m i l l i o n yea rs-the p e r i o d of a b u n dant fo s s i l s .

QUATERNARY Recent Pleistocene

12 12 11 22 5 72

TERTIARY Pliocene Miocene Oligocene Eocene Paleocene

CRETACEOUS

JURASSIC

DEVONIAN

SILURIAN

ORDOVICIAN

I A dot i n d i cates extincti o n . �4 An arrow i n d icates that the � group persi sts to present. 31

P R E-C A M B R I A N T I M E i n c l u d es the vast p e r i o d of ea rth h i sto ry w h i c h elapsed b efo re the d e p o s i t i o n of t h e Ca m b rian fos s i l -bearing rocks. It covers a period of a b o u t 4,500,000,000 years -o r a p p ro x i mate ly 9/10 of t h e total age of the eart h . This g reat period of t i m e witnessed the de足 ve l o p m e nt of t h e eart h , seas and atm o s p h e re , t h e o r i g i n o f l ife, a n d t h e early devel o p m ent o f l i v i n g th i n g s . B u t v e ry few fos s i l s of o rg a n i s m s even from t h e late P re-Ca m b rian have been fo u n d . M o st of those a re p l ants. L i m e-secret i n g algae fl o u r i s h ed i n t h e seas o f M o ntana, A l be rta a n d R h odesia. P re-Ca m b rian d e p o s its o f anth racite a n d s o m e

l i mesto n e s a re i n d i rect e v i d e n c e of the ex i stence of l ife. P r i m itive aquat i c f u n g i and algae have been fo u n d i n Pre-Ca m b ri a n c h e rts from O nta rio, a n d i n rocks o f M i c h i gan , M i n n es ota, En g l a n d a n d Scotl a n d . P re-Ca m b ri a n a n i mal foss i l s a re rare. A j e l lyfi s h i s known f r o m t h e G ra n d C a n y o n a n d s o m e t ra i l - l i ke m a rk i n g s from rocks in M o ntana. Recently d i scovered A u st ra l ian d e p o s its have revea led m o re a n i m al foss i l s . It seems l i kely t h at P re-Cam brian a n i m a l s were s oft bod i ed a n d t h e refo re poorly p reserved as fo s s i l s . By early Ca m b rian t i m e s , a n u m ber of d ifferent g roups devel oped har d parts a n d fo s s i l s b e came m o re c o m m o n . T h e d i st r i b u t i o n o f P re-Cam b rian rocks i s w o r l d w i d e . T h e y a r e m o st exte n sively expo sed i n t h e s h i e l d a reas , w h i c h a p p ea r to have re mai n ed m o re o r less sta b l e , p o s i t i v e l a n d a reas t h ro u g h o ut g e o l o g i c t i m e . T h e l a n d s o f t h e s e P re-Ca m b rian d a y s m u st h a v e b e e n startl i n g l y d eso late - a barren w i l d erness of bare rocks. In t h e s h a l low seas that l a p p ed these a n c i e nt wastel a n d s , l ife evolved, alth o u g h fos s i l s g i ve b ut few c l u es to the o ri g i n of l ife a n d i t s e a r l y d e ve l o p m ent. H owever, b i o c h e m i ca l experi m e n ts s u g g est ways that early o rg a n i c materials may h ave formed. Late P re-Ca m b rian foss i l s from Edi acara Hills, South A u stral i a, are the o l d e s t w e l l - p r e s e rv e d a n i m a l s . (After Glaessner)

S E G M ENTED WORM , Spriggina {loundersi, 1 .5 i n . WORM , Dicl<insonia cos/ala, 2.5 i n . J E L LYFISH, Medusina mawsoni, about 1 i .

A M i d d le Cam b rian sea, based on

spec i m en s from the B u rgess Shale of British C o l u m bia. 1. jel lyfi s h ; 2. tri l o b ite Neolenus and 3. s keletal

remai n s ; 4. a rach nid Sidn eyia; 5. c rustacean Marella; 6. s p o nge Vaux足 ia; 1. worm Mis/wia; 8. inarti c u late b rac h iopod Acrothele.

PALEOZOIC ERA T H E C A M B R I A N P E R I O D (600 m i l l i o n years a g o , first

period of the Pal eozo ic) is n a m ed from Wa l es (Lati n , Cambria) , w here rocks o f t h i s a g e were first stu d i ed . I n the Lower C a m b r i a n , the first co m m o n a n d w i d e s p read foss i l s occ u r: a l g ae, a rt h ro p o d s , b rac h i o p o d s , s p o n ges, coe l ente rates, worms, m o l l u sks a n d ec h i n o d e r m s . A l l l ived i n t h e sea. I t is s u r p r i s i n g to fi n d s o m a n y relatively co m p lex g ro u ps in the o l d est fo s s i l-bea r i n g rocks. But i n many ways C a m b rian a n i mals a re p r i m itive. Brach i o pods a re rep resented by the i na rtic u l ate forms (p. 82) a n d the ech i n oderms by p r i m itive ed ri oastero i d s . Most tri l o b ites were la rge, b ut a few (th e a g n ost i d s a n d eod isci d s , p p . 94-95) were a m o n g the smal l est and least o rn a m ented . T h e first o stracods ap peared i n the Lower C a m b rian . Mo l l u s ks were m o stly rep resented by t i n y sea s n a i l s (gastro p o d s), 34

Two u n u s u a l ly w e l l - p reserved M id足 d l e Cam b r i a n trilo bites (Oienoides) w ith i m p re s s i o n s of antennae and legs. La rger cara pace 3.2 i n . l o n g .

From a photo by Smithsonian Institution

b ut b ivalves (pel ecypods) ap peared in the U p p e r Cam足 b rian. C a m b r ian a l gae were very s i m i l a r to the i r very s i m p le P re-Ca m b ri a n a n cesto rs. M i d d l e C a m b rian B u rg ess S h a l e in B ritish C o l u m b i a conta i n s rem a rka b l e foss i l s -i n c l u d i n g soft-b o d i e d worms and sea c u c u m bers. The seas i n whi ch t h ese c reatu res l i ved occ u p i ed two g reat s u b s i d i n g be lts (geosyn c l i n es) i n N o rth A m e rica. Cam b rian rocks have a thi c k n ess of over 12,000 ft. in parts of the Rocky M o u nta i n s . See pp. 72-74 and p . 75 onward for more examples and details o f the animals and plants shown in the h abitat groups of this section.

M id d l e O rdovician sea fl oo r, showing straight- s h e l l e d , nautiloid cephalopods 1. En doceras, 2. Saclo足 ceras; 3. t r i l o bite Flexicalymene; b rach iopods 4. Ra{inesquina, 5.

Rhynchotrema; c o ra l s 6. Strepte足 lasma, 7. Favistella; gastropods 8. Maclurites, 9. Cyclonema; 1 0. pelec足 ypod Byssonychia; 1 1 . b ryozoans Hallopora.

T H E O R D OV I C I A N P E R I O D (425 to 500 m i l l i o n yea rs

ago) was named for the O rd ovi ces, an a n c i ent C e ltic tri be. The O r d o v i c i a n Period saw the r i se of new a n i m a l g ro u p s of g reat i m po rta n ce. Bony frag m e nts f r o m t h e M i d d l e O r d o v i c i a n of C o l o rado a n d Wyo m i n g a re evidence of the o l d est verteb rates , but we do n ot yet k n ow m u c h a b o ut these fish-l i ke c reatu res . Tetracoral s , g ra pto l ites , ech i n o i d s , astero i d s , c r i n o i d s a n d b ryozoans a l l a p peared for the first ti me, wh i l e the a rti c u late b rach i o p o d s (p. 82) far o u tn u m be red the i na rt i c u late. Most of the tri l o b ites were d ifferent from those of the C a m b r i a n . S o m e cep hal o p o d s reac hed a l e n gth of 13 feet. . I n parts of N o rt h A m e rica a n d Eu rope, O r d o v i c i a n seas cove red a reas that had been l a n d d u ri n g C a m b r i a n ti mes. Vo lcan oes bel c h ed l ava l o ca l l y. U p l i ft a n d m o u n ta i n b u i l d i n g o cc u rred i n easte rn N orth A m erica. N ot a l l the 36

A frag ment of b o n y armor of an ostracoderm fi s h (Astraspis), the oldest known verte b rate. M iddle Or dovician, C o l o rado.

rocks l a i d d o w n in those ancient seas conta i n the same fos s i l s . L i m esto nes a n d s hales a ro u n d C i nc i n n ati , O h i o , conta i n beautiful l y p reserved b rach i o p o d s , cora l s , b ryo z oa n s , m o l l u s ks , tri l o b ites and cri n o i ds. B l ack s h ales of the same age in New Yo rk, Que bec a n d Wa les co n ta i n g ra pto l ites a n d occa s i o n a l tri l o b ites. D iffe rent O rd ovician envi ro n m e nts e n a b l ed d ifferent a n i mals to p ro s p e r i n each reg i o n . M ost co m m o n were s h a l l ow-water l i me a n d m u d depos its n oted f o r t h e i r wel l-p reserved fossi l s . T h e repeated a n d w i d e s p read i nvas i o n o f N o rt h A m e r ica by Ordovician seas has p r o d uced exte n s ive Ordovician sed i m e nts. Outcrops of these rocks occ u r w i dely over m uch of t h e c o n t i n ent. Some O rd ov ician s ed i ments a re i m po rta nt o i l p ro d ucel'!t, a n d O rd o v ician s lates a re q ua r ried i n Ver m o nt. O u t c r o p s of O r d o v i c i an r o c k s .

\ ,, •,,

S i l u rian coral reef showing crin oids 1. S cyphocriniles, 2. Eucalyptocri足 niles; 3. starfi s h ; 4. a eu rypterid Euryplerus, 8 i n . l o n g ; corals 5. Favo-

sites, 6. Halysiles, 7. Xylodes; 8. cephalopod Cyrtoceras; 9. g astro足 pod Beraunia (Cyclolropis); 10. tri lo足 b ite Cheirurus.

T H E S I LU R I A N P E R I O D (fo r S i l u res, an a n c i e nt t r i be

of the We l s h borderland) l asted from 425 to 405 m i l l ion yea rs ago. Its fau nas d iffer fro m th ose of the O rdovi c i a n i n t h e p resence o f n ew fa m i l ies a n d g e n e ra , rather t h a n ih the a p peara n c e of com p l etel y new g ro u ps of a n i ma l s . In fact, the m ost i m po rtant n ewcomers are n ot a n i m a l s , b ut p l a nts. Fos s i l s of the o l dest l a n d p l a nts come from the U p per S i l u rian of A u stra l i a ( p . 1 51 ) . Frag me nts of w h at may be sti l l earl i e r land p l a nts h ave rece ntly been fo u n d in the Ordovician of Poland a n d southeastern U n ited States. Some of the best S i l u ri a n foss i l s ( i n c l u d i n g a l g ae, cora l s , stro m ato p o ro i d s , b rac h i o pods, c r i n o i d s and trilo足 b ites) come from the a n c i ent reefs i n S i l u rian l i m esto nes, s u c h as those near C h i cago. Scorpi o n - l ike eu rypte r i d s , 38

J AMOYTIUS, 10 i n . , a p r i m itive ag nathan fi s h (p. 1 32) with scales, lateral eyes, a n d a term i n al mouth. Silu rian.

,c:l'i:�ai��mii;;;;;;;ijj;:> •

BIRKENIA, a n ag nathan fi s h a b o u t 4 i n . lo n g . lacks pai red fins and true jaws. Silurian, Scotla n d .

some n i n e feet l o n g , l ived in estuaries and lag o o n s . Sev eral types of fi s h a re we l l p reserved in parts of the U p per S i l u ri a n . S i l u ri a n vo lca n ic act i vity occu rred in many a reas , and i n Sca n d i navia a n d B rita i n m o u nta i n b u i l d i n g took p l ace at the close of the P e r i o d . In oth e r p l aces, d e s e rts and l a n d - l ocked seas were present in w h ich salt depos its accu m u l ated , s uch as those of N ew York, O h i o a n d Mich i g a n . Th ese dep os its a re st i l l w o rked as i m po rtant com mercial s o u rces of salt. O utcrops of S i l u rian rocks a re co m m o n in easte rn N orth A m er ica. A s i n t h e Ordovician Period, t h e c h a racter of the rocks a n d of the foss i l s i s eviden ce of w ides p read and g e n e ral l y s h a l l ow seas .

D evo nian fi s hes. A com pos ite d i ora ma sh()w i n g 1. Bothriolepis, a placo derm about 1 4 i n . lo n g , 2. Dinichthys, a g i ant 30-ft. m a r i n e placo d e rm,

largest vertebrate of this period, and 3. C/adosela ch e, a 3-ft.-lo ng primi tive s hark.

THE D E V O N I A N P E R I O D began a b o u t 405 m i l l i o n years ago a n d e n d ed a b o ut 6 0 m i l l i o n years later. It saw the g reat expa n s i o n of fi s hes, land pla nts, a n d the fi rst l a n d a n i m a ls ,. p ri m itive a m p h i b i a n s . Th e fi s hes ( p p . 132138) i nc l u d ed several k i n d s ofjaw less fis h (ostracoderms), plate-skinned fish (placoderms), sharks and the first bony

fi s h es (osteichthyes ) . From o n e g r o u p , the l o be-fi n fi s hes (crosso pte ryg i a n s ) , the fi rst a m p h i bia (ichth yosteg i d s) a ro se. These s h ow a m ixtu re of fish a n d am p h i b i a n char acte rs. These u n u sual fos s i l s , fro m a wa r m , m o i st envi ro n m e nt, were fo u n d in m o u nta i n s of G reen l a n d . S k u l l s of a Devo n i a n fis h , Eusthenop teron, and a p r i m itive a m p h i b i a n , l chthyostega. Correspo n d i n g b o n e s a r e i n s a m e color. N ote sim ilar bony

plates i n both skulls but also larger eyes, n ostrils, stouter jaws, a n d loss of gill cove r i n g i n the head and skull of the a m p h i bi a n .

A D e v o n i a n f o r e st w i t h 1 . a t ree t e r n ,

a p r i m i t i v e l y c o p o d Protolepidoden足

Eospermalopleris; 2. a s m a l l p r i m i 足 t i v e l e a f l e s s p l a n t , Psilophylon ; 3 . a s c o u r i n g r u s h , Calamophylon; 4.

dron; and 5. t h e o l d est- k n o w n a m 足 p h i b i an

and

fi rst

land

verteb rate,

/ chlhyoslega, 2Y, ft. l o n g .

The o l d est s p i d e rs, m i l l i pedes and i n sects ap pear i n the Devo n i an, as d o fresh -water clams. Ea rly l a n d p l ants were s i m p l e, lac k i n g true roots a n d l eaves, but with the vasc u lar o r c o n d u ct i n g system fo u n d in all later l a n d p l ants. Late i n t h e Devo n i a n , g reat fo rests o f s c a l e trees and seed fern s were w i d e s p read .

Corals 1 . Heliophyllum, 2 . Cylindrophyllum, 3. Hexagon aria, 4. Syn aptophyllum, 5. Heterophrentis,- 6. Pleurodictyum, 7. Chonophyllum; 8. bryozoan Fenes-

A Devonian coral reef.

trellin a; brachiopods 9. Leptaen a, 1 0. A tryp a; 1 1 . gastro pod Platyceras; 12. cephalo pod Michelinoceras; tri足 l o b ites 1 3. Ca/ymene, 1 4. Anchiopsis; 1 5 . crinoid Dolato crin us.

Devonian coral reefs include large cup corals two feet h igh and compound corals eig ht feet across. H orn corals were numerous and varied. Brachiopods and mol lusks continued to fl ourish ; the first common ammonites ap足 peared,

but true graptolites were already extinct and

trilobites were greatly reduced in numbers. In many con足 tinental areas thick deposits of red sands and muds ac足 cumulated.

A colony of M i s s i s s i p p ian c r i n o i d s 1 . Cyalhocriniles, 2. Taxocrinus, 3 .

Batocrinus, 4. Barycrinus, 5. Scylalocrinus; 6. a brittle star Onych asler.

T H E M I S S I S S I P P I A N P E R I O D is n a m ed for t h e l i m e足

sto n e b l uffs a l o n g the M i s s i s s i p p i R i v e r w h e re typ ica l o utcro ps occu r. It was a period (345 to 31 0 m i l l i o n years ago) of s h a l low, warm seas, in w h ic h cora l s , b rach i o p o d s , cri n o i d s , b lasto i d s , b ryozoan s a n d fo ra m i n ifera fl o u ri s h e d . I n p l aces t h ese foss i l s a re so a b u n dant t h at t h e y make u p m ost o f t h e rocks. O n l a n d , a m p h i b i a conti n u ed to deve l o p , w h i le l a n d p l a n ts s p read i n a l l m o i st a reas a n d antici pated the g reat coal swam p fo rests of the Pen n sy l va n i a n . Much of N o rth A m erica except t h e fa r west and t h e east coast was u n d e r wate r d u r i n g M i s s i ss i p p i a n t i m e .

A P e n n sylvanian coal swamp. T rees

i n c l u d e lycopods 1 . Sigillaria, 2. Lepidoden dron; 3. s p h enopsid Cal足 amites; 4. seed fern s ; 5. Cordaites;

6. a labyri nthod o nt a m p h i b i a n ; 7. Meganeura, an i n sect w ith a 30- i n . w i n g span rel ated t o the m o dern d ragonflies.

THE P E N N SY L V A N I A N P E R I O D - (31 0 to 280 m i l l i o n years ago) was named after t h e g reat coal-beari n g strata of P e n n sylvan i a. It saw the d eve l o p ment of lowl a n d s , g reat swa m p s , a n d de ltas s u rro u n ded a n d ofte n covered by s h a l l ow seas. Some of the land was ba rren san d deserts ( E n g l i s h Mi d l a n d s ) , o r salt bas i n s (Co l o rad o ) . G reat t rees , s o m e 1 50 feet h i g h , formed the coal fo rests i n low swa m p y l a n d that w a s often fl o o d e d . Most co m m o n were the sca l e trees (lyco p o d s ) , s e e d fe rns (pteri d o s p e r m s ) , h o rseta i l s and corda ites. H e re l i ved g iant "d rago nfl ies , " w ith a 3044

One of the o l dest known and s i m plest rep足 tiles, Tudilanus pun ctulatus. M i d d l e P e n n足 sylvanian fro m O h i o . 4 i n .

i nch w i n g s pa n , a n d many kinds of a m p h i b i a n s . Pen n s y l 足 van i a n rivers a n d deltas were i n habited by cou ntless clams, other s h e l lfish a n d fishes. This period a l so saw the e m e rg e n ce of the re pti l es from am p h i b i an ancesto rs. In ad d it i o n to Tuditanus (ab ove) , foss i l s rep resen t i n g fo u r g ro u p s o f p r i m itive rept i l es have been f o u n d i n t h e s h a l es of Kansas. The seas co nti n u ed to s u p po rt rich i nverteb rate l ife, w h ich i nc l u d e d a b u n da n t s p i n d le-s h a ped fora m i n ifera (fu s u l i n i d s ) , co ra l s , b rach i o po d s , m o l l u sks, b ryozoa n s , cri n o i d s , o straco d s a n d a few tri l o b ites. Outcrops o f P e n n sylva n i a n rocks.

A Perm i a n l a n d s ca p e . Reptiles i n clude 1 . Dimetrodon, 1 0 ft. l o n g, a " s a i l - ba c k e d "

carnivore ;

Sey-

mouria, 2 ft. lo n g . A m p h i bi a i n cl u d e 3. Eryops, 6 ft. l o n g a n d 4. Diplo caulus, 2 ft. lo n g ,

TH E P E R M I A N P E R I O D (280 to 230 m i l l i o n years ago)

began with ty p i ca l coa l -forest p l ants, w h ic h were later re p l aced by p rimitive co nife rs, especia l l y in se mi-arid u p l a n d regi o n s . I n parts of the Southern H e mi s p h e re the most co m m o n pla nts we re a d i sti n ctive g ro u p of t o n g u e f e r n s (Glossopteris). Ma ny n e w i n s ects appeared , i n c l u d i n g beet l es a n d true d rag o n fl ies. Strea m s a n d ponds conta i n ed a vari ety of fi s h es . Am p h i b i a n s fl o u r i s h ed a l o n g thei r ban ks, b ut were overshad owed by n ewer, m o re act ive repti l e s . Ea r l y repti l es d iffered fro m a m p h i b ia o n ly in d eta i ls of the s k u l l a n d verteb rae. Sey m o u ria m o rp h s were sq uat, l u m b eri n g rept i l es abou t two feet l o n g , with fl at, ' massive h eads. Fossil e g g s from the Lower Pe rmia n of Texas, the o l d est l a n d eg g s k n ow n , may b e l o n g t o t h e m . Ot her repti les were q u ite d ifferent. Dim etrodon , the sai l - backed l i zard , was a savage carn i 46

MESOSAURUS, a n e e d l e- t o o t h e d a q u a t i c r e pt i l e . Pe n n s y l v a n i a n - Perm i a n . 1 6 i n .

v o re, a b o ut 1 0 feet l o n g . Edaphosaurus, a vegeta r i a n , w a s a l s o a sa i l b ac k . The p u rpose of t h e s e s a i l s i s o b s c u re . They m a y h ave served as p r i m itive temperatu re c o ntro l s . Other Perm ian rept i l es i n c l u d ed mesosa u rs , s m a l l , l o n g 足 s n o uted , a q uatic c reatu res, a n d other s p e c i e s s i m i la r , b u t u n re l ated , to m o d e r n l i z ard s. A n other g ro u p , t h e t h e r i o d o nts ( b ea st teet h ) , k n o w n f r o m S o uth Afri ca a n d R u s s i a , were s m a l l , ag i l e ca r n i v o res, f r o m w h i c h m a m 足 m a l s a re d e s c e n d e d . Cynognathus w a s a ty p i c a l t h e r i o 足 d o nt, a b o u t 6 feet l o n g , with a d og l i ke s k u l l , a n d d iffer足 entiated teet h . Its l e g s , p l aced b e l ow the b o d y , l i fted it c l ear of the g ro u n d . T h i s was a better a d a ptat i o n to a A

Perm i a n

reef

west

T e xa s .

Diclyoclostus. 2 . Dielasma; 3. p ro d u c t i d ; 4. Leptodus Brachiopods

s h el l s ; s p o n g e s 5. Girlyocoelia, 6. Heliospong ia; c e p h a l o p o d s 7. Stenopoceras, 8. Coap eroc eras.

m o re active l ife t h a n t h e s p raw l i n g legs of a m p h i b i a n s a n d p r i m itive rept i l es . The c l ose of th e Perm ian ma rked the e n d of the PaleoÂ zoic Era -the first g reat c h apter in the reco rded h i sto ry of l ife. By t h e n , m a n y a n i mals a n d p l a nts w h i c h had d o m i Â n ated t h e Paleoz o i c scene h a d become exti n ct. F u s u l i n i d fo ra m i n ifera, vari o u s b ryozoa n s , rug ose cora l s , p ro d u ct i d b rac h i o p o d s , t ri l o b ites a n d b l asto i d s a l l van i s h ed , a s well as m a n y c ri n o i d s a n d cep h a l o p o d s . G i ant s c a l e trees d w i n d led in n u m bers. Âˇ Most h o rseta i l s and m a n y fe rns became ext i n ct. A m p h i b ia and some fish u n d e rwent a d rast i c red u cti o n . Why t h i s happened i s n ot c l ear, b ut it may have been c o n n ected with extreme c l i matic c h a n ges d u ri n g t h e late Permian when seas were very restri cted and l a rge, h i g h conti n e nts e m erged. In m a n y a reas, c o ra l reefs fri n g ed t h e s h o res of deserts a n d vast i n l a n d salt lakes fo r m e d . Exte n s ive g l ac i e rs cove red parts of the Southern H e m i s p h e re. N ew m o u nta i n c h a i n s slowly rose, the A p pa l ac h i a n s and the U ra l s among them .

TYR A N N OS AURUS, the largest carnivorous d i n o sau r, was a bo ut 50 ft. l o n g with a 4- to 5-ft. s k u l l . C reta ceous o f M o nta n a .

T H E MESOZOIC ERA The M esozoi c ( M i d d l e Life) Era covers a p e riod of a bout 1 65 m i l l ion years, d u ri n g w h i c h rept i l es so overs hadowed all ot her a n i m a l s t h at it i s often cal l ed t h e " A g e of Rep t i l e s . " G reat c h a n g es took p l ace in some i n verteb rates too. N ew form s replaced those w h i c h had b ecom e exti nct at the e n d of t h e P a l eozoi c. A m mon ites d ev e loped ra p i d l y u n t i l cou ntless n u m b ers l i ved i n the seas. B i rd s , m a m m a l s , floweri n g p l a nts a n d many mod e rn i n s ects a p peared for the first t i m e . El m , oa k, m a p l e and other mod e r n b road l eaved trees became com mon. The d evelop m e n t and s p read of some flower i n g p l a nts d e p e n d ed on t h e para l l e l d evelop m e nt of i n sects w h i ch pol l i n ated t h e flowe rs. Ot h e r i m porta nt g eog ra p h i c c h a n g es were a l so taki n g p l ace. N ew patte r n s of l a n d s a n d seas for m e d . N ew mou n tai n r a n g e s s low ly e m e rg e d . A s the res u lt o f severa l re lated g eolog i c p roc esses, g reat m i n e ral d e posits were form ed. S i xty m i l l ion years later, we sti l l d e pe n d on many of these d e posits for ou r m eta l s a n d o u r f u e l s . 49

A Triassic s e m i - a r i d l a n d scape. The

repti l es i n c l ude 1. Cynogn alhus, a 7-ft. m a m m a l - l i ke ca r n i vore ; 2. Ma足 chaeroprosopus, an a l l i g ato r-like

phytosa u r ; 3. Salloposu chus, a 4-ft. thec o d o n t ; 4. Kannemeyeria, a 6-ft. herbivorous d i cy n o d o nt m o re com足 mon i n the u p l a n d s.

T H E T R I A SS I C P E R I O D (230 to 1 80 m i l l i o n years ago)

was n a m ed from a th reefo l d d i v i s i o n of its rocks. In many p l aces T riassic rocks resem b l e those of the Perm i a n P e r i o d -th ick seq u ences o f r e d s h ales a n d s a n d sto nes, d e p o s ited i n te m p o ra ry l a kes, deserts a n d bas i n s. Vo l 足 can i c acti v ity w a s co n s i d e ra b l e, as i n easte rn N o rth A m e r ica fro m Vi rg i n ia to C o n necticut. A g a i n st th i s backg ro u n d the repti les develo ped a n d esta b l i s h ed t h e i r maste ry. The i r adva nced b o d y structu re a n d s h e l l - p rotected eggs e n a b l ed them to s u rv i ve c h a n g 足 i n g a n d ofte n adverse cl i m ates , a n d t o co l o n ize n ew a reas w h ich were fo r b i d d e n to the wate r-tied a m p h i b i a . The fi rst d i n o s a u r s a p pea red ; th e i r footp r i nts a re a b u n d ant in some rocks, as i n th e Co n n ectic ut Va l l ey. 50

N o r was the d o minance of reptiles co nfi n ed to la n d , for i n o p en oceans d o l p h i n - like ichthyosau rs swept th ro u g h t h e water. Late r 15- t o 20-foot l o n g p l e siosau rs pad d l ed thei r way t h ro u g h Triassic seas. N ew types of s p o n ges and p rotozoans deve l o ped. The modern hexacora l s ap peared , and n ew g ro u ps of b rac h i o pods re p l aced t h e i r Permian fo rebears. Gastro p o d s a n d pelecy p o d s i n c reased i n n u m bers. A m m o nites fl o u rished a n d u n d e rwent c o n s i d e ra b l e c h a n g e . Lo b ster-like a rt h ro pods and mod ern ech i n o i d s and c ri n o i d s fi rst appeared in the Triassic. Cycads and p r i mitive c o n ifers fl o u rished o n u p la n d areas. The Pet rifi ed Fo rest o f A ri z o na c o n ta i n s fossi l s o f t h ese trees. Fe rns a n d sco u ri n g r u s h e s p ro s pered i n l ower, m o i st a reas. .

.. �� .__,(' ..., ,/:. /

;

G e n e ra l i zed d i o rama of J u rassic mari n e rept i les s h ow i n g 1 . Ichthyo足 saurus, 1 0 ft. lo n g ; 2. Plesiosaurus, about 1 2 to 20 ft. l o n g ; 3. Eurhinosau-

THE J U R ASSI C PER I O D is named from the J u ra

M o u ntai n s . It began about 180 m i l l i o n years ago a n d lasted about 45 m i l l i o n years. Of a l l its a b u n dant a n d exotic l ife, n o n e was m o re typ ical than the d i n os a u rs of w h ich there were th ree ma i n J u rassic g ro u ps : first, the sau ropod s , l o n g - n ecked , l o n g -ta i l e d , fo u r- l e g g ed m o n sters, w h ich i nc l u d ed the largest land a n i mal (Diplodocus, 87 ft. l o n g ) ; seco n d , steg osau rs, a r m o red repti l es that weig h ed u p to 1 0 to n s (w ith o n l y a 3-oz. brai n ) ; th i rd , the ca r n ivo rous theropods w h ich wal ked o n their h i n d legs, i ncl u d i n g Allosaurus, a savage, 35-ft. creatu re. Others were m o re s l e n d er, a n d s o m e were o n l y 3 feet l o n g . A few early, 52

rus, about 1 7 ft. lo n g ; 4. Cryplocleidus, about 1 0 ft. l o n g , U p p e r J u ras足 s i c ; 5 . s q u i d - l i ke b e l e m n ites fleeing in a p rotective c l o u d of " i n k . "

d uck-b i l led h e r b ivoro u s d i n o sau rs l u m b ered across the swa m p y l ow l a n d s . Flyi n g re pti les g l i d i n g t h ro u g h t h e a i r i ncl u ded s par row足 s i zed s pecies a n d others up to 4 feet l o n g w ith s l e n d e r cl u b - l i ke tai l s . Ichthyosau rs a n d p l esiosau rs were t h e carn iv o r o u s m a sters o f the ocea n s . H osts o f a m m o n ites (some up to 6 feet in d iamete r) t h ro n ged the shal l ow seas , tog ether with gastro p o d s , pelecypods, s q u i d s (belem足 n ites ) , ech i n o i d s , cri n o i d s a n d fo ram i n ifera. The J u rass ic a l so saw the deve l o p m ent of two g ro u ps that were later to estab l i s h thei r d o m i nance. The o l d est mammals are known from foss i l f rag m e nts of rat-s i zed 53

S h o re of a J u ra s s i c lagoon at S o l e n h ofe n , G e r m a n y . 1 . fi rst b i rd , Archae opteryx; 2. fl y i n g reptiles, Rhamph�

rhynchus; 3 . s m a l l b i p e d a l d i nosau r, Compsognalhus about 2 ft. lo n g ; a n d 4 . cycadeoid plants.

jaws and teeth from western Un ited States and E u ro pe. The S o l e n h ofen J u rassic l i m esto ne of Bavaria conta i n s rem a i n s o f A rcha eopteryx, t h e o l dest k n ow n b i rd . J u rassic p lants i n c l u d ed the n ow exti n ct cycadeo i d s w i t h s h o rt, th ick t r u n ks . T h ese were crowned w ith frond l i ke l eaves a n d o rnate re p ro d u ctive st ru ctu res w h i c h c l o s e l y resem b l ed mod ern fl owers. Cyca d s , c o n i fers, ferns and g i n kg o s were com m o n . G i n kg os were w i d e s p read a l l t h ro u g h t h e Mesoz o i c b ut later b ecame a l m o st ext i n ct. Today o n ly a s i n g le species s u rv i ves but t h i s is w i d e l y p l a nted . O v e r a t h ousand species o f i n sects a re k n o w n , i n c l u d i n g m a ny m odern forms. 54

A J u rassic swamp w i t h h e r b i v o ro us

d i no sau rs. 1 . Brontosaurus, a 67-lt. l o n g s a u r o po d ; 2. Diplodocus, a

s i m i l a r , but mo re s l e n de r , 87-ft . - l o n g a n i m a l ; 3. Stegosaurus, a 20-ft . - l o n g a rmo red d i n o s a u r .

A d i o rama of C reta ceous reptiles.

D i n o sa u rs i n c l u d e 1. Triceratops, y o u n g a n d a d u lt, 20 ft. l o n g ; 2. Trach-

odon, a 40-ft. d u c K-b i l l d i n osau r ; 3. Tyrannosaurus, a powerf u l c a r n i足 vore, 50 ft. l o n g ; 4. o s t ri c h - l i ke Slru-

THE C RETACEO U S PER I O D (na m ed f rom c h a l k , its

most c h a racte r i stic d epos it) began about 135 m i l l ion years ago and la sted som e 70 m i l l ion yea rs. It was one of the most i m po rta nt of a l l g eolog ic p e riod s, m a r ked by a m ajor ad vance of the sea in many parts of t h e worl d , a n d b y t h e g reat t h i c kness of both marine and continenta l sed i m ents . A g reat d e p ress ion connected the A rcti c Ocean w ith the G u lf o f M e x i co. M i d d l e Eu rope w a s a l so s u b m erged except for a central land mass. Towards the c lose of th i s period ea rth movem ents p rod u ced mountain rang es w h i c h a re now the And es and the Rockies, as we l l as mou nta ins in Anta rct ica a n d n orth easte rn A s i a . The C retac eou s Period m a rked both the c u l m ination of Mesozo i c l ife and th e foresh adowing of a n i m a l s and 56

lhiomim us, 5 ft. h i g h ; 5. Brachio saurus ( Lower C reta c eo u s) ; 6. Pter anodon, a fl y i n g rept i l e w ith a 25-ft.

w i n g span. Pla nts i n c l u d e 7. cyca d e o i d s and 8. p r i m itive a n g i o sperms o r fl owering p l a n t s .

p l a nts that were later to d i s p lace it. The m ost i m p o rta nt new arrivals were the fl oweri n g p l a nts (an g i o s p e r m s ) . T h ey first ap peared i n the Lower C retaceo u s , b ut eventu ally t h ey beca m e the d o m i nant p l a nts o n every conti n ent. Many fa m i l iar l i v i n g trees and sh r u b s, i n c l u d i n g th e p o p lar, mag n o l ia, oak, m a p l e , bee c h , h o l ly, i vy and l a u re l ap pea red d u r i n g t h e C retaceo u s . The s p read of the fl ower ing p l a nts also had i m p o rtant effects o n a n i mal l ife, for they p ro v i ded n ew s o u rces of food f.o r m a m m a l s , b i rd s , rept i l es a n d i n sects. T h e s u bseq uent expa n s i o n of mam ma l s a n d b i rd s d ep en ded very largely u po n these n ew food s u p p l i e s . D i n o sa u rs exte nded thei r d o m i n a n ce a c r o s s C retaceo u s l a n d s . T h ey a re k n o w n from every conti nent, a n d i n c l uded 57

In a C retaceous seascape 1 . Tylo足 saurus, a 26-ft. mosasaur, c h ases 2. Arch elon, a 1 2-ft. marine t u rtle.

Ham merheaded fl yi n g repti les, 3. Pter anodon, w ith a 25 ft. w i n g s pan, are overhea d .

many u n u s u a l types. H o rned d i n o sa u rs (ce rato p s i a n s ) were co m m o n , as w e r e t h e a r m o red a n ky l o sa u rs , a n d the b i zarre d uck-b i l l s with t h e i r stri k i n g a m p h i b i o u s adapta足 t i o n s . The g reat q u a d r u ped d i n osau rs d ecl i n ed in t h e C retaceo u s b u t savage carn i v o res w e r e co m m o n . Tyran足 nosaurus stood 20 feet h ig h a n d had a sku l l over 3 feet l o n g . Oth e r ca r n i v o res were m uch s m a l l e r. Flyi n g rept i l es were rep resented by Pteranodon , a tooth less, h a m m e r足 headed creatu re with a w i n g s pa n of 25 feet, the l a rgest a n i ma l ever to fl y . I n the s e a s , g i ant t u rtles ( Arch elon) reached a l e n g t h o f 1 2 feet, a n d s o m e plesiosa u rs g rew o v e r 40 feet l o n g . Ichthyosau rs decl i n e d . Savage, serpent-l ike m osasa u rs , some 3 5 feet l o n g , were sea-g o i n g l izards. 58

A late C retace o u s sea ftoor s h o w i n g a rich variety of m o l l u sks. A m mo足 n ites 1. Heliocer as, 2. Baculites, 3.

Placenlicer as; gastropods 4. Turri足 lella, 5. oth e r ; pelecypods 6. oysters, 7. Pecten.

Two wel l -k n ow n types of fos s i l b i rd s occu r in C reta足 ceo us rocks. /ch thyornis, a s le n d e r, te r n - l i ke b i rd a b o u t 8 i nches h i g h , w a s a stro n g fl i er. Hesp erornis, i n co m p l ete co ntrast, was about 4 X feet h i g h , a d i v i n g b i rd , with power足 ful sw i m m i ng legs b ut o n ly vestiges of w i n g s . It also had l o n g , to oth ed jaw s . Ma m m a l s were s m a l l a n d relatively i n s i g n ificant. Th e i r rem a i n s a re rare, re p resented b y s m a l l p r i m itive fo r m s that s u rvived f r o m t h e J u rassic a n d a l so by two n ew g ro u ps, t h e o p o s s u m-l i ke po uched mars u p i a l s a n d t h e i n sectivores, fo reru n n ers o f the s h rews. The foss i l s a r e m o stly teeth a n d pa rts of l ower jaws, w h ic h , beca u s e of th e i r u n i q u e structu res, a re sufficient to d i st i n g u i s h t h ese true mammals from m a m m a l - l i ke rej't i l e s . 59

I n the s h a l l ow seas i n v e rteb rates l i ved i n g reat d i vers ity. The dom i n ant g ro u p was the a m m o n ites, w h i c h s h owed many u n u s u a l fo rms. Be l e m n ites, pelecypods and gastro pods of rat h e r modern ap peara n ce, cora l s , sea u rch i n s a n d fora m i n i fera also fl o u r i s h e d . Modern bony fi s h (te l e osts) were c o m m o n . T h e cora l s , a b u n d ant loca l l y i n C retace o u s beds, show a bas i c s i xfold s y m m etry. C r i n o i d s also deve l o ped n ew forms, i n c l u d i n g a free-sw i m m i n g , ste m less cri n o i d with s l e n d e r arms u p t o 4 ft. l o n g . Inoceramus m o l l u s ks ( p . 1 1 8) , som eti mes 3 t o 5 ft . across, were w i d e l y d i stri b uted . The close of the Cretaceo u s saw the w i d e s p read ex t i n ct i o n of many of the d o m i nant a n i m a l s of t h e Mesoz o i c Era. D i n o sau rs, pterosau rs, i c hthyosa u rs , p l e s i osaurs, mosasa u rs , a m m o n ites, true b e l e m n ites, many pelecypods a n d cora l s a l l became exti nct. It was as t r u l y the e n d of an e ra i n the l o n g h i sto ry of l ife as was the Perm i a n , a n d the c a u s e s for t h i s w i d es p read decl i n e are n o less d iffi c u lt to i d e ntify. It is p ro b a b l e , h owever, that t h e g reat geo l o g i cal c h a n ges, and the changes i n p l a n ts exerci sed a p rofou nd effect on many g ro u p s of a n i ma l s .

BRONTOT HERIUM, an 8-ft . - h i g h N o rth A m e ri can g raz i n g m a m m a l , o n e of t h e ext i nct titanothe res. O l i gocene of South Dakota.

THE CEN OZOIC ERA The C e n o z o i c Era i n c l u d es the last 70 m i l l i o n years of earth h i sto ry. It i s far m o re fa m i l i a r t h a n p rev i o u s eras, for alth o u g h some a n i ma l s and pla nts d i ed o ut other k i n d s h ave s u rv ived without d rastic c h a n ge and a re a l i ve today. S l ow but stri k i n g c h a n g e s i n c l i m ate took p l ace d u ri n g t h i s t i m e. P o l a r reg i o n s c o o l ed and the g e n e ra l warm tem perate c l i mate gave way t o a w i d e r c l i matic ra n g e . T h e conti n e nts were s i m i l ar to those of today, alth o u g h t h e re was m o u nta i n b u i l d i n g , conti n e ntal warp ing and v o l ca n i c activ ity. C e n o z o i c strata in t h e G u lf Coast, Cal ifo r n ia, t h e M i d d l e East a n d the East I n d ies are n ow i m p o rta nt petro l e u m p ro d u cers. C e n o z o i c l ife (the A g e of Mam mals) is d o m i nated by t h e m a m m a l s a n d fl oweri n g p l a nts. M a m ma l s re p l aced the ru l i n g re p tiles of the Mesoz o i c i n every e n v i ro n m e nt. T h e fl oweri n g pla nts became b road ly s i m i lar t o l i v i n g f o r m s . A m p h i b i a and repti les beca me relatively i n c o n s p i c u o u s . Bi rds c o n t i n ued t o e x p a n d i n n u m bers a n d variety. T h e b o n y fi s h (te leosts) o utn u m bered a l l oth er fi s h by twenty t o o n e . M a r i n e i n verteb rates to o k o n a m o d e r n l o o k . Gastro pods and pelecypods became the m ost a b u n da nt, a n d cep h a l o p o d s a n d b rac h i o p o d s were g reatly red u ced . T h i s t h e n i s the last g reat era i n t h e l o n g h i sto ry of l ife -the · p re l u d e to t h e p resent. 61

A d i ora ma of Lower T e rtiary life. 1 . Diatryma, a 7-ft . - h i g h carnivoro u s b i rd . M a m ma l s i n c l u d e 2. Notharctus,

a l e m u r - l i ke p r i mate ; 3. Coryphodon, a 3-ft.-h i g h a m b l y pod ; 4. Hyracoth e足 rium ( E o h i p p us) the a n c estral 4-

T H E LO W E R T E RT I A RY P E R I O D ( P a leocene, Eo足

cene, and O l i g oc e n e) in N o rth A m erica is re p resented by g reat conti nenta l , bad land d e p o s its w h i c h conta i n m a n y m a m m a l i a n fo ss i l s. Th ick m a r i n e d e p o s i ts fo rmed i n south -eastern U. S . a n d a l o n g t h e Pac ifi c Coast w h e re volcanoes a l s o e r u pted . Lower T e rt i ary fo s s i l s a re stri k i n g ly d i ffe re nt from those of t h e C retaceo u s . Ma m m a l s i n c reased e x p l o s i vely, s p read i n g i nto a l l env i ro n m e nts a n d b eco m i n g adapted to many ways of l ife on l a n d , water a n d in the a i r. Mam足 m a l i a n h i story va r i e d . In i s o lated Tertiary S o uth A me ri ca a g reat d iv e rs ity of m a rs u p ial m a m m a l s d ev e lo ped. Other mars u p ia l s stil l s u rv i ve i n t h e i s o lati o n of A u st ra l ia. Ea rly Tert i a ry m a m ma l s i n c l u d ed p r i m itive rodent-s i z ed fo rms, i n s ectivores a n d mars u p ia l s , t h at h ad persi sted 62

toed, 1 2- i n c h - h i g h h o rse ; 5. Uinla足 therium, a rh i n o c e ro s-si zed h o r n ed m a m mal. T rees are palms and b road-

leaved a n g i o s p e r m s s i m i lar to mod足 ern te m p e rate or s e m i -t ro p i cal s pecies.

from the C retaceo u s . N ew species i n c l u d ed two m a i n g ro u ps, h o ofed m a m m a l s and carn ivore s . C reodonts, fo re r u n n ers o f the carn i v o res, and c o n d y足 larth s , fo re ru n n ers of h oofed mam mal s, were s o m ew h at s i m i l a r, p ifferi n g m a i n l y i n deta i l s of teeth a n d feet. Both were s q uat, h eavy- l i m be d , about t h e size of a co l l ie, w ith d o g - l i ke h eads a n d five b l u ntly c lawed toes o n eac h l i m b . T h e i r b ra i n s were s m a l l a n d p ri m it ive. Other n ew a rrivals were ancest ra l rodents and p r i mates, rep resented by lem u r- l i ke a n i m a l s . A m b l y p o d s were h eavy, c l u m sy, hoofed m a m m a l s , w ith b road feet. The early ones we re s h eep-s i z e d , b ut the l ater k i n d s ( u i ntathe res) were seven feet h i g h , as big as a l a rg e rh i n oceros, w it h t h ree pa i rs o f b l u n t h o r n s . The m a l e s had large d o w n -cu rved t u s ks . 63

An O l i g ocene l a n d scape i n c l u d es 1 . Mesohippus, a th ree-toed h o rse, 2 ft. h i g h ; 2. Bronlops, a 1 4 ft. h o r n ed titan oth e re ; 3. Orecdon, a s h ee p s i zed h e rb i vo r e ; 4. Baluchilherium,

a 1 8-ft.- h i g h r h i n o ceros, the largest land m a m m a l ; 5. Prolapiris, a tap i r ; 6 . Hyaenodon, a c reodont c a r n i vore ; a n d , 7: l a n d tortoises. Slylemys, (feed i n g on g rasses).

D u ri n g Eoce n e t i m e s m o re adva nced m a m m a l s d i s p l aced m a n y o l d e r forms i n N o rth A m e rica a n d E u ro pe. These n ew arrivals i ncl u d ed true rodents, m a i n ly s q u i rrel l i ke s pecies, a n d a variety of rh i n oceroses ( o n e O l i g ocene g iant, Balu chith erium, m eas u red 18 feet h i g h at the s h o u l ders). A n cestral ta p i rs, tita n otheres a n d t h e first even toed h o ofed m a m m a l s also ap peared . T h e ea rly tita n o theres w e r e S fT! a l l , h o r n l ess b rowsers w ith c l u m sy b o d i e s a n d t i n y b rai n s . C o n d y l a rt h s , creo d o nts a n d u i ntat h e res persi sted for a t i m e , b ut l o st o ut to l ater arrivals s uch as ea rly h o rses (the th ree-toed , co l l ie-si zed Mesohippus) , g iant p i g s , ancestral ca m e l s , o reodo nts, masto d o n s a n d l a r g e sabe r-tooth ed cats . 64

O reodo nts were s h ee p - s i zed, l o n g -ta i led h e rb ivo res that s u rv ived u nt i l the P l i ocene. Tita n otheres were h u ge, g rotesq ue h o rn ed beasts. The cat fam i l y fi rst appeared in the form of the earl i est sabe r-toot h , Hoplophon eus, abo ut the s i z e of a m o u ntai n l i o n . Lower Tertiary b i rds were mod ern i n a p pea rance, but i ncl u d ed n u m b ers of large, g ro u n d -l i v i n g g e n e ra, o n e of w h ich , Dialrym a, was 7 feet h i g h . Fi s h , too, were of m o d e r n aspect. The fine fresh -water sed i m ents o f the G reen R i ver beds of Wyo m i n g have y i e l ded t h o u s a n d s of beautif u l , we l l - p rese rved fi s h fos s i l s . Ma r i n e i n ve rteb rates were very m uch l i ke m od e rn fo rms. Large fora m i n ifera ( "Numm ulites") a b o u n ded i n the s h a l 足 low s e a s of the Med iterran ean and Cari b bea n . P la nts re足 sem b l ed l i v i n g fo rms, b ut pal m s g rew i n Canada, a n d te m p erate o a k a n d wa l n ut fo rests i n A laska. There was m o u nta i n b u i l d i n g and cru stal d i stu rbance in the A l p s , Carpath i a n s , Pyren ees, A p e n n i n es, and H i malayas. The Coast Ran g e of western N o rth A m erica was the sce n e of m o u n ta i n b u i l d i n g too, with volcan ic activ ity.

A M i o c e n e l a n d scape. 1 . a w i l d p i g , Dinohyus; 2. a s m a l l r h i n o ceros, Diceratherium ; 3. ho rse- l i ke Moro-

pus; 4. a fou r-tusked masto d o n , Trilophodon ; 5. a h e r d o f p r i m itive camels, Stenomylus.

U P P E R TERT I A RY P E R I O D ( M i ocene a n d P l i oce n e) lasted a b o ut 2 5 m i l l i o n years, e n d i n g a b o ut a m i l l i o n years ago. It is ma rked by the conti n u ed rise of m o d e rn m a m m a l s . C ha n g es i n v o l v i n g b ra i n , l i m bs a n d teeth and the acco m pan y i ng expa n s i o n o f m a m m a l s a s a g ro u p were closely re lated t o cl i mat ic c h a n g es. Over wide a reas of N o rt h A m erica conti n ental u p l ift p ro d uced d ri e r c l i mates , and co nverted l u s h lowland fo rests i nto g rassy p ra i ries. The o l d est co m m o n g rasses come f ro m t h e Mi oce ne. Ma n y m a m m a l i a n c h a n g es were associated with the c h a n g e from b rows i n g to g raz i n g h a b its. C h a n g es of t h i s kind are particu l ar l y wel l i l l u strated i n the h o rse fa m i l y. S o m e of t h ese chan ges were correlated with i ncrease in overa l l s i ze, b ut others were n ot. Th u s h o rse teeth beca m e larger a n d deeper, b u t they a l s o be足 came h i g h -crow n e d , with a s q u a re, i nfo l d e d , chew i n g s u rface. T h e l i m b s became l o n g e r a n d chan g ed i n re l ative p r o p o rti o n s , b ut the n u m ber of g ro u n d-to uch i n g toes was TH E

E V O LUTI O N OF TH E H O RSE RESTO R A T I O N

4-toed

red u ced . T h i s refl ects a rad ical c h a n g e from a fl at-footed to a ti p-toe, s p r i n g-h oofed po stu re. Feed i ng o n to u g h p ra i ri e g ra sses demanded to u g her teeth , a n d t h e advan tag e of s peed o n the hard, open prai ries favo red t h e new foot structu re. W i d e s p read c h a n g e s also took p l ace in ot her g ro u ps of m a m m a l s . A n cestral e l e p hants, cam e l s , r h i n oceroses, dogs and s m a l l e r carn ivores a bo u n ded. Oth e r fo rms have n o l i v i n g desce n d a nts. Moropus resem b l ed a c l u m s i l y c o n structed h o rse w i t h c l aws. O n e g iant p i g h a d a s ku l l fo u r feet l o n g . Th ere were g i raffes, cam e l s , a n d the pa thetic ante l o p e , Syn dyoceras, with the stra n g est h o r n s of any of its tribe. Sabe r-toothed cats cont i n ued, and ape l i ke c reat u res (Dryopithecus) s p read across E u rope a n d Africa. M a n y o f the o l d e r type m a m m a l s became exti n ct towa rds t h e c l ose of P l i ocene t i m e s . M o st U p per Tertiary mari ne i n verteb rates a n d p l a nts a re barely d i st i n g u i s h a b l e from modern s pecies. Re n ewed earth m ovements in the A l ps , H i m a l ayas and a l o n g t h e Pacific Coast o f N o rth A m erica com p l i cated a n d ex ten ded ex i sti n g m o u nta i n ra nges. O u r h u rried exc u rs i o n t h ro u g h g e o l o g i c t i m e has taken us, w ith g iant steps, over a period of m o re than half a b i l l i o n years from the l ate P re-Ca m b rian to t h e e n d of t h e Tert i a ry. T h e l ate Tertiary world i s modern except fo r m i n o r species deve l o p ment i n c l u d i n g the ex p l o s i ve d o m i n a n c e o f m a n . T h o u g h fos s i l c l ues a re m eager, the pano rama of l ife i s u n de rstandable becau se of t h e l e n gth of g e o l o g ic t i m e . The slow o rga n i c c h a n ges w h i c h led to ext i n ction o r s u rvival a re the b u i l d i n g bl ocks of evo l ut i o n a n d , f o r t h e i r o peratio n , time i s needed. M a n ' s develop ment i s a matter of o n l y a few m i l l i o n years , but a b i l l i o n years o f p reparati o n l i e beh i n d it. 68

A P l eistocene l a n d sc a pe with 1 . woolly m a m m o t h , Elephas primi足 genius, 12 ft. h ig h ; a n d , 2. a w o o l l y r h i n o ceros, Coe/odonla, 6 ft. h i g h .

T H E Q U AT E R N A RY P E R I O D i n c l u des the m o ment i n

w h i c h we now l ive, together w i t h the P l e i stocene E p o c h , w h i c h b e g a n a b o u t one m i l l i o n yea rs ago. C o n t i n ental i ce s h eets, u p to ten t h o usand feet t h i c k, s p read over m uc h of the N o rth er n H e m i s p h e re in at l east fou r g la c i a l advan ces, the last of w h i c h retreated a b o ut 1 1 ,000 years ago i n N o rth A m er i ca. A n ta rct i ca and the m o u nta i n s of the S o uthern H e m i s p h e re were a l so g l aciated . There i s e v i d e n c e of repeated fl o ral a n d fa u na l m i g ra足 t i o n s in res p o n se to c l i matic c h a n g es . D u ri n g the c o l d e r e p i sodes vast h e r d s of w i l d p i g s , c a m e l s , b i s o n a n d e l e足 p h a nts ra n g ed across N o rt h A m e rica, E u rope a n d A s i a . There w e r e fo u r A m erican s pecies of e l e p h a nts, i ncl u d i n g t h e I m pe r i a l Mam m ot h , 1 4 feet h i g h at t h e s h o u l d e r, with c u rved t u s ks 13 feet l o n g . 69

S MILODO N , la rgest of saber足 toothed cats, had upper ca n i n e teeth 8 i n . l o n g . N o rth A me r i ca. P l e i stocene.

Majestic woo l l y m a m m oths, w h ich roa med acros s the tu n d ra of E u ro pe , A s i a a n d N o rth A m e rica, a re p i ctu red in early cave pa i n t i n g s . Most of th ese l a rg e m a m m a l s be足 ca m e ext i n ct near the e n d of the P l e i stoce n e. Carn i vo res , i ncl u d i n g wol ves, foxes, bad gers, a n d the terri b l e saber足 tooth Smilodon , a re w e l l known from the P l e i stoce n e ta r p o o l s of Ca l ifo rn ia. H u ge armad i l l o - l i ke g l y pto d o nts a n d g i ant (20 ft. h i g h ) g ro u n d s l oths h a d evo l ved i n South A m e rica a n d s p read i nto N o rth A m e rica w h e n the l a n d b r i d g e b etween t h e t w o cont i n ents w a s re-esta b l i s h ed i n late P l i ocene ti m e s . I n th i s a r i d a n d partly frozen w o r l d , man e m e rged .

T H E E M E R G E N C E OF M A N CRO-MAGNON m a n , fi n e l y b u i lt,

ta l l , m u sc u l a r, with modern brain a n d facial feat u res, r e p l aced Nean d e rthal. H e m a n ufactu red fi n ely wo rked tools f r o m stone, ivory and bone, practiced cere m o n ial b u rial and was probably advanced socially as w e l l . Cro-Magnon cave paintings, d raw i n g s a n d sc u l pt u re are beauti fully executed . NEANDERTHAL m a n l ived over a w i d e area of E u r o p e a n d N o rth Africa d u ri n g the l ast g l acial advance. He was s h o rt, stocky, stooped, with h eavy brows, retreat i n g forehead a n d a p ro m i n e n t but c h i n less jaw. A cave d w e l l e r and s k i l led h u nter, he practiced c e r e m o n ial b u ri a l . H e b e c a m e ext i n ct after about 1 00,000 years. Not a n cestral to m o d e r n m a n , but probably from same sto ck.

scraper

PITHECANTHROPUS (the ape

man) i s k n o w n from specimens about 500,000 years o l d from Java and C h i n a . H e i g ht about 5 ft. , semi erect posture, heavy b rows, power ful jaws with man l i ke teeth a n d a brain capac ity between that of the large apes a n d modern man. C h arred bones found with s i m p l e stone tools s u g g est c a n n i b a l i s m . h a n d axe of S o . Africa a n d h i s relative, Zinjan lhropus , of O l d u vai G o rge, E. Africa, a re m o re than 1 Y, m i l l i on yrs. o l d . A recent O l d uvai d i scovery is an ad vanced fossil man, Homo habilis, a h u nter w h o p r o b a b l y b u i lt s i m p l e s h e lters a n d made m o st o f the too l s fo u n d with t h e s p l it bones o f game h e ate. Oth e r d i scoveries have p u s h ed the age of m a n ' s d i rect a n cesto rs back to about 20 m i l l i o n years.

kn ife

AUSTRALOPITHECUS

I N V E RT E B R A T E FO S S I LS The fossils described on pages 72-1 29 all represent ani足 mals that lack backbones (invertebrates). Most lived in the sea, and most are now extinct. For these reasons they are less familiar than most vertebrates and plants, and the terms used to describe their structure are not widely known. H owever, small structures are important in iden足 t i fication of invertebrates. The following diagrams (pages 72, 73, 74) show structures of the most common inverte足 brate fossils. They provide a gu ide to ten major groups, and indicate the meanings of terms used later in the text.

For m o re a b o u t i n v e rteb rate fo s s i l s read : Buchsbaum,

A N I M A LS W I T H O U T

B A C K BO N E S ,

Rev.

Ed.,

Univ.

C h i c ago P r e s s , 1 959. A very c l e a r a n d read a b l e c o l l e g e text. G o l d r i n g , W . H A N D BO O K O F PA L E O N T O LO G Y FOR B EG I N N E R S A N D A M A T E U R S , P a l e o n t o l o g ic a l R e s . I n s t . , I t h a ca, N . Y. A n o l d e r g u i d e with e m p h a s i s o n N e w York State. M o o re, La l i c k e r & F i s c h e r , I N V E RT E B R A T E FOSS I LS , M c G raw-H i l l , N . Y.,

1 952. A c o m p l ete and a u t h o r i tat ive a d v a n ced c o l l eg e text. S h r o c k and T w e n h of e l , P R I N C I P L ES OF I N V E R T E B R A T E P A L E O N TO L O G Y , M c G raw- H i l l , N . Y . , 1 953. A m o d e r n , c o m p r e h e n s i v e refe r e n c e .

T Y P I CAL I N VERTEBRA TE S T RUCTU R E S B R YOZ O A N

S I M PLE CORA L c o l u me l l a

c o ra l l i te

aperture of zooec i u m

POSTE R I O R

DORSAL

h i n ge line

AN足 TERIOR

ribs

pa l l ial l i n e ANTERIOR

B R A C H I O PO D GASTR O P O D

scars

VENTRAL

P ELECY P O D CEP H A LO P O D exte r n a l v i e w

transverse o rn a m e n t

i nternal sect i o n

ante r i o r canal

' :r:.

g labella

ia l s u t u r e

��=��

c rm

�;�

genal spine

thorax

seg m e nt

TR I LO B I T E

CRINOID

EC H I N O I D

G RA PTO L I T E t u bercle

u n iserial

b i se r i a l

R A D I O LA R I A

P ROTOZO A N S a re m i n ute, aq uatic o r paras itic a n i

mals w h ose s i n g l e c e l l performs a l l t h e l ife f u n ct i o n s . A few s pecies a re v i s i b l e, b ut most a re m i c ro sc o p i c . Of t h e many d iff�re n t g ro u p s of p rotozoa n s , o n l y fora m i n ifera a n d rad i o l a r i a (Class Sa rco d i na) are co m m o n as fos s i l s . Fora m i n ifera (Ord o v i c i a n - R ece nt) u s u a l l y have tests o r s h e l l s of c e m e nted fore i g n particles, o r o f l i m e. The s h e l l s o f rad i o l aria (Ca m b ri a n - Rece nt) a re o f s i l i ca o r o f stro n t i u m s u l p h ate. Fo ra m i n ifera ( i l l u strated b e l ow) and rad i o l a ria (a bove) a re so a b u n d ant that t h e i r t i n y s h e l l s cover t h o u s a n d s of s q u a re m i les of ocean fl o o r a n d form g reat d e p o s its of ooze. S o m e l i m e sto n es are com posed largely of foram i n ifera. Petro l e u m g eo l o g i sts use fora m i n ife ra to i d e ntify a n d correl ate strata. FORAMI N I FERA

Globigerin a

Hyperammina

Endothyra

Triticites

Cam erina

D entalin a

.....

STRUCTU RE OF A S I M PLE SPON GE

S P ICULES serve as a

HYD N O CERAS, Dev.-

" s keleto n " i n many s p o n g e s . They a re c o m m o n m i c rofoss i l s .

Miss., a n octag o n a l , c o n ical s i l ica s p o n g e . Length a b o u t 5 i n .

S P O N G E S o r Porife ra ( p o re-bea rers) a re t h e s i m p lest

m u lticel l u lar a n i ma l s . Wate r i s d rawn i nto the sac-l i ke body t h ro u g h m a n y m i n ute p o res a n d is swept a l o n g by the w h i p - l i ke flagella of t h e co l lar ce l l s . Micro sco p ic food particles a re taken from the wate r, w h ich i s expelled t h ro u g h the top o pe n i n g of the s p o n g e . The s p o n g e ' s s u p p o rt comes fro m a skeleton o f need l e足 l i ke s p i c u l e s , made of l i m e or s i l ica, or from a fl e x i b l e skeleton o f s po n g i n , a s i n t h e bath s p o n g e . S p icu les a re co m m o n m icrofo s s i l s . M ost s p o n ges are mari ne, g row足 ing attached to the botto m . Some may be as s m a l l as a p i n h ead, oth ers m o re than 40 i nches l o n g . Foss i l s p o n g e s a re fo u n d i n Cam b ri a n t o Rece nt rocks . ASTRAE OS P O N G IA,

VE N TRICUL ITES ,

RECEPTACU L I TES,

S i l u r i a n . S a u c e r- s haped s p o n g e , w i t h p r o m i n ent s p i c u l e s . D i amete r 2 i n .

C ret. C o n i cal s p o n g e , w ith i rregu lar, perforated wal l s . Length 4 i n .

Ord.- D ev . G l o b u lar t o d i s h - s h a p e d . Affinities o b s c u re. D i a meter 6 i n .

C o m m o n Sea A n e m o n e

Fossil Coral

COE L E N T E R A T E S are s i m ple aq uatic a n i m a l s i ncl u d 足

i n g co ra l s , s e a a n e m o n es, sea p e n s a n d fa n s , t h e t i n y h yd ra a n d the exti nct stro m ato po ro i d s . Mo st coe lenterates l i ve in the sea ; many a re co l o n i a l . T h e i r sac- l i ke b o d i es have a two -layered wa l l a n d a s i n g l e o p e n i n g s u rro u n d ed by tentacles. They h ave sti n g i n g ce l l s ( n e m atocysts) b u t lack adva nced o r g a n syste m s , s uch as t h e res p i rato ry, excreto ry, ci rcu l atory and n e rvo u s systems of h i g h e r a n i 足 ma ls . J e l l yfis h lack hard parts, b ut co ra l s a n d thei r k i n secrete h o r n y o r l i m y " s keleto n s . " T h e b o d y p l a n o f coe足 lenterates has a rad i a l sym m etry. T h e i r re p r o d u ct i o n often alternates a sexual stage, the f ree-sw i m m i n g m e d u sa, w ith an asex u a l stage, the attached p o l y p . C o r a l s are i m p o rtant rock b u i l d ers. Ma n y trop ical i s l a n d s are w h o l l y o r part l y coral l i mesto ne. Liv i n g reef- b u i l d i n g cora l s a re co n fi n ed t o a n e q u ato rial belt o f wa rm, s h a l l ow waters. Most req u i re a m i n i m u m water temperat u re of 70属F. a n d d o n ot g row o n m u d d y b otto m s o r, beca use of darkness, at d e pt h s g reater than about 1 50 feet. Foss i l coral reefs a re m o re w i d e l y d i strib uted. S o m e o f t h e m a re imp o rtant petro l e u m reservo i rs. T h e i r p resence i n b oth the A rctic and A n ta rctic i n d icates c l i matic co n d it i o n s very d ifferent f r o m t h e p rese nt. Coelente rate fo s s i l s a re fo u n d from t h e Pre-Ca m b ri a n to Rece nt. 77

STROMATOPOR O I D i nt e r n a l v i ew s h owi n g layers external view s h o w i n g po res COELE N TERATE FOSSILS i n c l ude stro

TABULATE CORAL Favosiles

m ato p o r o i d s , ext i n ct s p o n g e - l i ke co l o n ial forms with s p h erical, bran c h i n g o r e n c r u sting s kel eto n s of l i me. C a m b r i a n - C retaceo u s . T h e corals (Class A n t h ozoa) i n c l ude fi v e m a i n g r o u p s , t h ree of w h i c h are extin ct. Tabu l ate corals ( O rd . - J u r.) are c o m p o u nd with stro n g l y d eveloped tabu lae, weak or absent septa a n d no col u m e l la. S c h i z oc o ra l s ( O rd . J u r. ) , often classified u n der tabu late c o rals, m u l t i p l i ed by fi s s i o n a n d u s u a l ly lac ked true s epta. T etraco rals o r r u g o s e c o rals have the m a i n se pta develo ped i n fo u r q uad rants. S o l i ta ry species a re ca l l ed h o rn corals ( O rd . P e r m . ) . The two l i v i n g s u b - c l a sses of coral a re the c o l o n ial octocorals (alcyonarians, T rias.-Rec.), w ith h o rny o r limy skeletons and e i g ht tentacles, a n d hexacorals (Trias.-Rec.), with a s i x-fold se ptal patte rn, i n c l u d ing reef b u i l d i ng corals.

TETRACORAL Caninia

P A LEOZO I C C O R A LS

STRE PTELA S MA, O r d . - Dev. Deep calyx.

Septa n u m e rous, altern ately long a n d s h o rt, th ickened at peri p h e r y ; d i s s e p i m ents weak. Length a b o ut 2 i n . HAL Y SITES, U . Ord.-L. Dev. C o m p o u nd " c h a i n-cora l , " s l e n d e r c o ra l l ites arranged in b ran c h i ng row s . Septa weak or a b s e nt ; tab u l ae str o n g . D i a m eter of c o l o n y about 2 o r 3 i n . LIT H O STROT I O N , M i s s . - P en n . C o l o n i a l coral w i th cyl i n d rical or p r i s m atic c o r a l l ites, stro n g septa, cen tral ta b u l ae, co l u m ella and peri p h e ral d i ssep i m e nts. Max. diam. of c o ral l ites a b o ut 0.5 i n . CYSTI P H Y L LU M, S i i . -Dev. S i m p le o r com pound cora l s of variable s h a p e ; i nterior fi l l ed w ith ves i c u lar d i s s e p i ments. Length a bout 2 i n . SYR I NGO PORA, S i i .- P e n n . , is c o m p o u n d ; cora l l ites d i sti nct with transverse con nec t i o n s , tabu lae f u n n el - s h a p e d , s e pta s p i n e- l ike. D ia m eter of c o l o n y a b o ut 3 i n . LO P H O P H Y L LI DIU M , P e n n .-Perm. S i n g le coral with p ro j ect i n g co l u m e l l a ; septa alter n ate in l e n gth ; a rc h ed ta b u la e ; no d i s sepi ments. Length a b o u t 1 i n . NEOZAP HREN TIS , M i s s . S m a l l , sol itary coral w i th o n e m a i n sept u m l o n g , o p p o s i ng one s h o rt ; o b l i q u e f o s s u l a on c o n vex s i d e of coral. I n c o m p l ete ta b u lae. No d i s s e p i m e nts. Length a b o u t 1 i n .

Cysliphyllum

Syringopora

M E SOZO I C A N D C E N OZ O I C C O E L E N T E RATES M ONTLIV AL TIA , T r i a s s i c to Ter tiary. A s i n g l e c o ral, c o n ical o r fl at tened, with a w r i n kled s u rfa ce, n u c m e r o u s s e pta, o uter e d g es toothed o r ridged, n u m e r o u s d i ssep i ments. Length from 1 to 3. 5 i n .

Triassic to Tert i a ry. C o m p o u n d c o ral with d e p ressed, fl ower- l i ke s u rface ; w a l l s of c o ra l l ites i n d i st i n c t ; septa strong, j o i n i n g adjacent c o r a l l ites ; small c o l u mella. D i a m . of c o lony 3-4 in.

STY LASTER. A n Eocene t o Re

EUSMILIA, O l i g o c e n e to Recent.

cent genus of c o l o n ial h y d rozoan with s l e n d e r bran c h i n g a n d with rad i ati ng apertures. A l so, pits with b u l g i ng margins are p resent. Length of ty p ical b ra n c h 2-3 i n .

A c o l o n i a l , bra n c h i n g , stony c o r a l . Septa are p r o m i nent a n d a re s e e n i n t h e w a l l s . No c o l u m e l la. O n e o f a n i m p o rtant and n u m e r o u s g ro u p . Length a b o u t 1 .5 i n .

T H A M N A STERIA ,

STRUCTURE OF AN INDIVIDUAL BRYOZO A N

BUGULA. A b u s hy col· o n y of a recent b ryoz oan. Each b r a n c h c o n s i sts of 4 c h a m bers (zooecia). B r a n c h e s 2·3 in. h i g h .

retracto r m uscles

B R YOZO A N S o r Mos s A n i ma l s are aq uatic, co l o n i a l a n i m a l s w ith encrusti n g , b ranch i n g , o r ta n - l i ke g rowt h . T h e s u p p o rti n g structu res a re h o r n y o r l i m y, a n d t h e m i n ute i n d i v i d u a l a n i ma l s a re h o used i n t i n y c u p s . B ryo zoans rese m b l e cora l s b ut a re m o re co m p l ex . They have n e rvo u s and m u sc u l a r syste m s and co m p l ete, U-s h aped d i g estive tracts. Most b ryozoans are marine a n d a re rela tively co m m o n foss i l s. I n co n s picuous b ryozoans a re u se f u l in co rrelat i n g st rata. O rd ov ician-Recent. ARCHIME DES, M i s s . ·

RHO MBOPORA,

FENESTRELLINA,

Perm. Lacy colony, g ro w i n g from a s c rew l i ke a x i s . 2 s p e c i e s s h o w n . Length 1 -2 i n .

Ord.·Perm. Slender b r a n c h e s , ofte n s p i n y ; c o n s p i c u o u s a p e rtu res. Length about 0.3 i n .

S i i . -Perm . Fan- or f u n n el-shaped c o l o n y ; two rows of a pertures o n one face. Len gth about 2 i n .

B R A C H I O PO D S o r La m p S h e l l s a re s m a l l m a r i n e i n 足 verteb rates. T h e i r va r i a b l e s h e l l s e n c lose the s oft body a n d oth e r i nternal str u ct u res i m p o rta nt i n i d e n tificati o n . T h e s h e l l i s made o f two u n eq ual valves. A t t h e poster i o r e n d of o n e ( t he ped i c l e val ve) i s an o pen i n g t h ro u g h w h i c h a fl eshy a n c h o ri n g stem (the ped i c l e ) emerges. T h e other valve i s t h e b ra c h i a l valve. O n e g ro u p , t h e i n a rt i c u late b rach i o p o d s ( b e l ow), has va lves of c h it i n a n d cal c i u m p h o s p hate h e l d toget h e r o n l y b y m u scles. T h e seco n d a n d l a r g e r g ro u p , a rti c u l ate b rac h i opods, has s h e l l s of l i me h e l d together by teeth a l o n g the h i n ge as w e l l as by m u sc l e s . T h e re a re ab out 200 species of l i v i n g b rac h i o pods a n d a b o ut 30,000 fo s s i l fo rms, fo u n d from the Cam b rian to the p resent. Ca m b rian b rac h i o po d s a re m a i n ly i na rt i cu足 l ate. Late r, a rti c u l ate fo rms became m uch m o re commo n w h ile i n a rt i c u l ate forms d e c l i n e d . B rac h i o po d s a re a m o n g the m o st a b u n dant Paleozoic fos s i l s . S o m e g rew u p to 9 i n ches across. M ost were about an i n c h in d i a m eter. A l th o u g h a d u lts l i ve m a i n l y attached, t h e y beg i n l i fe as free-swi m m i n g la rvae, w h ich I N A R T I C U LATE

B R A C H I O PODS

L I NG U L A , O rd ovic ian t o Recent. T h i s l i v i n g fo s s i l , a

widely d i s t r i b uted b u r rowing form, has a th i n p h o s足 p hate s h e l l a n d a l o n g ped icle. Length about 1 to 1 .5 i n . O B O LE L L A , Lower Cam b. ; equal, sub-circular valves marked by fi n e con centric g rowth l i n es. Length about 0.2 i n .

LINGULEL L A , Cam b. t o

L. Ord. i s b roadly tea rs h a ped w i t h a g ro ove i n s i de the ped i c l e valve. M a x i m u m l e n gth 1 i n .

A RT I C U L A T E B R A C H I O PO D S A rt i c u l ate brac h i o po d , Magellania, shows ( 1 ) the p e d i c l e valve above and b rac h i a l valve below. The red d ot ma rks the end of the h i n g e l i n e . I nterior structures ( 2 ) i n c l u d e t h e brac h i d i a ( b l ue), m u sc l e s ( r e d ) ,

m u sc l e scars (g ray) a n d p e d i c l e (yel l ow). T h e i nterior of t h e b rac h i a l valve ( 3 ) s h ows t h e l o o p e d brac h i d i a ( b l u e ) , m u s c l e scars ( g ray), a n d h i nge sockets (black). Foss i l s show足 i n g i n terior struct u re may occur.

acco u nts for t h e i r w i d e g eo g ra p h ic d i st r i b uti o n . Lack of a ped icle o pen i n g i n the s h e l l i n d icates that some fo s s i l b rach i o p o d s d i d not have a f u n cti o n a l ped icle. N e a r l y a l l fos s i l fo r m s l i ved i n s h a l l ow wate r. So d o m o st o f the l i v i n g s peci es , t h o u g h s o m e h ave beco me a d a pted t o g reater depth s . P LA N ES O F S Y MMETRY

S u perfi c i a l l y , b rach i o p o d s res e m b l e p e l e c y p o d s ( p . 1 1 6). B o t h h ave 2 s i d ed o r b i l ateral s y m m etry. I n brac h i o p o d s a l i n e d i v i d i n g the s h e l l

i nto t w o s i m i l a r h a l v e s r u n s t h r o u g h t h e valves (as s h o w n above). I n pelecypods t h e l i n e r u n s between t h e two valves.

LOWER PA LEOZ O I C D I NORT H I S , M i d d l e t o U p p e r O r足

d o v i c i a n , is an e x a m p l e ot a l a r g e c o m m o n g r o u p ( o rt h i d s ) . A l l h a v e b i co n vex p rofi l e , a stra i g ht h i n ge l i n e a n d fi n e rad i a l r i b s . L e n g t h 1 i n . p e d i c l e v iew

p rofi l e

H E B E RT E L LA,

M iddle to

Upper

O r d o v i c i a n , i s a m a s s i ve s h e l l w i t h ped i c l e v a l v e r a t h e r fi a t . B ra c h i a l

pedicle v iew

v a l v e stro n g l y c o n v e x ,

s o m et i m e s

w i t h a s t r o n g f o l d ; fi n e rad i a l r i b s . L e n g t h 1 .2 i n . ZYGOS P I RA,

Middle Ordovician

to L o w e r S i l u r i a n , i s a s m a l l , s t ro n g l y n b b e d s h e l l w i t h a s u b ro u n d e d o ut足 l i n e and

b i c o n v ex p ro fi l e .

Ped i c l e

v a l v e d e e p e r t h a n b ra c h i a l , w i t h a b r a c h i a l v i ew

p e d 1 c l e v 1 ew

strong

fo l d .

Common

t h r o u g h o ut

t h e O h i o V a l ley a n d in the A p p a l ac h ia n s . L e n g t h 0.3 to 0.7 i n .

RAF I N E S Q U I NA, M i d d l e

to U p p e r O r d o v i c i a n ,

is a

l a r g e , fi a t , s e m i c i rc u l a r s h e l l w i t h a l o n g , s t ra i g ht h i n g e l i n e . B r a c h i a l v a l v e i s flat o r c o n cave ; the p e d i c l e v a l v e i s c o n v e x . F i n e r i b s , s o m e足 ti mes

a l t e r n at i n g

size.

T h i s b r a c h i o p od a p p a ren t l y l o s t its p e d i c l e at m a t u r ity.

b r a c h i a l v i ew

Length 1 .3 to 1 .7 i n . p ro fi l e

BRACHIOPODS PLATVSTRO P HIA, M i d d l e Or d o v i c i a n to M i d d l e S i l u r i a n , has a massive, stro n g l y ri bbed s h e l l with a c o n vex o u t l i n e and a long, stra i g ht h i ng e l i n e. L e n g t h to 1 .7 i n .

PETROCRANIA o n Ra{inesquina, M i d d l e O r d o v i c i a n to P e r m i a n . A s m a l l , l i m y i n a rt i c u late b rac h i o p o d . P e d i c l e v a l v e c e m ented (often to an other s h e l l ) ; brachial valve l ow, c o n i c al. Length 0.3 to I i n . LEPIDOCVCLUS (Rhyn colrema) .

M i d d l e to U p p e r O r d o v i c i a n , has a r i b b ed s h e l l often with " h e r r i n g b o n e " pattern. Stro n g l y i n flated , s u b - c i r c u l a r p r o fi l e . S h o rt h i n g e l i n e Brac h i a l valve has a f o l d . Parti c u l a r ly c o m m o n i n the O h io V a l ley. Length 0.3 to I .3 i n .

p ro fi l e STRO P H O M E NA, M � d �

t o U p per O r d o v i c i a n . O u t l i n e s i m i l a r to Ra{inesquina, b ut with a c o n cave p ed i c l e valve a n d a c o n vex b rac h ia l v a l v e . It has its str o n g e st c u rvat u re near t h e a nterior edge ; fa ne r i b s . L i k e Ra{ines quina, it p r o b a b l y l o st its p e d i c l e at matu rity · a n d rested o n t h e bott o m . Length 0.6 t o 1 .4 i n .

LOWER

AND

M I D DLE

A T R Y P A , M i d d le S i l u rian to lower M i s s i s s i p p ia n . Ventral valve s l i g htly, a n d brachial stro n g l y c o n vex ; ribs varia.ble, sometimes frilled. A wi d e足 s p read foss i l . Len gth 1 to 1 .3 i n .

poste r i o r v i ew

D A L M A N ELLA, Lower S i l u ri a n . A

s m a l l brac h i o pod with a s u b - c i r c u l a r o u t l i n e . V a l v e s c o n vex, ped i c l e stro n g l y so. F i n e r i b s a n d g rowth l i nes. Oth e r c h a racteristics i nternal. Length a b o u t 0.4 i n .

p rofile p rofile

EOSPIRIFER, M id d l e S i l u rian to

lower Dev o n i a n . An early, not very typical s p i r ifer. Su b-oval outl i n e, convex valves with a b road fold a n d very fi n e ribs. Has s p i ral b ra c h i d i a . L e n g t h 1 to 1 .3 i n .

DICOELO SIA, f o r m e r l y called B i l o b ites, U p per Ordovician to lower

Devon i a n , h a s a stro n g ly b i l o bed outl i n e , n a r row h i n g e a n d very fi n e r i b s . L e n g t h a b o u t 0.3 i n .

anterior v i ew

P A L EOZO I C B R A C H I O PO D S SCHUC HERTELLA, Lower Devo足 n i a n to P e r m i a n , i s a brac h i o p o d with a wide h i n g e l i n e ; v a l v e s ftat o r g e n t l y c u rved ; fi n e r i b s . O t h e r c h a r足 acters are i n te r n a l . Length about 1 i n .

i n t e r n a l cast

p ro fi l e

p rofi l e

MER I S T I N A, M i d d le S i l u r i a n , h a s a l a rge, stro n g l y c o n vex s h e l l w i t h a l ow fold in t h e b r a c h i a l valve. Smooth su rface. Other i d e ntify i n g featu res a re i nterna l . Length about 1 i n .

b ra c h i a l v i ew

P E N T A MERUS, M i d d l e S i l u r i a n . A large, stro n g l y co nvex s h e l l with s m ooth valves and a strong beak. I nterior casts, as i l l u strated, s h ow a strong vertical p l ate in the ped i c l e v a l v e . M a x . l ength 3 i n .

RHYNCHOTRETA , S i l u r i a n , is t ri a n g u la r in o u t l i n e w ith a s ha r p b e a k , p r o m i n e n t p ed i c l e o p e n i n g and v e r y s t r o n g r i b s . L e n g t h 0.5 i n .

p rofile

B R AC H I O P O D S

pedicle v i ew

LEPTAENA is a c o m m o n a n d w i d e足

s p read b ra c h i o p o d of M i d d l e O rd o足 v i c ia n to M is s i s s i ppian age. The pedicle va l ve is co n vex a n d the b ra c h i a l val v e i s c o n cave, g i v i n g the STROPHEODONTA, Devonian. S e m i -ci rcu l a r outline w ith a wide h i nge. B rac h ial v a l ve is gently con足 cave, pedicle valve convex ; fi n e r i b s. Has large m u sc l e scars a n d other featu res internal. M a x i m u m l e n gth about 1 in.

s h e l l a n u n u s u a l p rofi l e. Valves are stro n g ly bent near the a nte r i o r edge a n d along the s i d es. The s u rface is cove red with v e ry fine radiating ribs and c o n c e n tric g rowth l i nes. Length 1 to 1 .5 i n . M i d d l e S i l u rian to Lower M i s s i s s i p p i a n , has a l a rg e, flat, trian g u lar area between h i n ge l i n e a n d beak of arched p e d i c l e valve. Larg e ped i c l e o p e n i n gs. Small, con足 vex b rachial valve. Length 0.7 i n .

CYRTINA,

p e d i c l e view

LINGULA, Ordovician to Recent.

I n a rt i c u late brac h i o pod has dark, broadly tear- s h a ped s h e l l with rat h e r fl a t p rofi l e . Stra i g ht anterior marg i n . See page 82 f o r l i vi n g species. Length 1 to 1 .5 i n . ped i ca l view

DIELASMA, M i s s i s s i p p ian to P e r

m i a n , has a l o n g oval o u t l i n e . Both b rach ial and p e d i c l e valve a re g e ntly convex. S u rface s m ooth with few mark i n g s . L e n gth to 0.8 i n .

Ordovician to P e r m i a n . I n a rt i c u late. Dark, s h i ny, c o n i cal b ra c h ial valve with c i rc u lar outl i n e a n d fi ne rings. T h e t i p of this valve i s frequently a bit off-center. D ia m ete r u s ua l ly a b o ut 0.5 i n . ORB.ICULOIDEA,

SPIRIFER, M i s s i s s i p p ian to Lower P e n n sylvan i a n , i s the typical mem b e r of the s p i riferid g ro u p of brach i o p o d s , w h i c h are c o m m o n i n many Paleozoic strata. S p i rifers s how g reat variat i o n in form but have i n ternal s p i ra l b rac h i d ia, a more or less triang u la r o utl i ne, a n d most have rad ial r i b s . Spirifer itself has a w i d e h i n g e l i n e, stro ng ribs and a c o n v ex p rofi le, with a c o n s p i c u o u s f o l d . I n some s pecies i n t e r n a l struc t u res are i m p o rtant i n identificat i o n . L e n g t h about 1 i n .

p rofi le

MUCROSPIRIFER, M i dd le to U p

per Devo n i a n , is m u c h w i d e r h i n g ed than Spirifer, w ith s h e l l often w i n g e d . C o n s p ic i o u s ribs and fold present ; other feat u res i nternal. Length a b o u t 1 in.

N EOS P I RI F ER, Pen n sylvanian to

P e r m i a n , a l a rge, ma ssive s p i riter with a wide s h e l l , is co nvex i n p ro fi l e . N ote the p r o m i nent h i n g e,

strong r i b s , and strong b u t vari a b le fo l d . Neospiri{er i s c o m mon t h ro u g h out the m i d -c o n t i n e n tal a rea. Length 1 to 1 .3 i n .

p e d i c l e valve

A RT I C U LATE

exte r i o r

i nterior

M E SOLO B U S , Lower Pe n n syl vanian, has a w i d e, stra i g ht h i nge, s e m i - c i r c u l a r o u t l i n e , a n d a d e p res sed p rofile. Note the s h a l low fold on the b rach ial va l ve and the v e ry fine ri bs. Length about 0.3 i n .

M i s s i s s i p p i a n to P e r m i a n . Large s h e l l s with wide h i n g e a n d strong beak. P r o m i nent r i b s , w i t h s o m e c o n c entric g rowth l i n es a n d a few s p i n es . P ed i c le v a l v e i s c o n vex. Length 1 to 1 .5 i n . D I CT Y OCLOST U S ,

b r a c h i a l v iew

p ro fi l e

M i d d l e S i l u rian to P e r m i a n , has a s e m i - c i r c u l a r o u t l i ne a n d a w i de h i nge with s p i n es a l o ng m a rg i n . B rach ial va lve con cave ; pedicle convex. F i n e r i b s a n d g rowth l i n es . Length 0.4 to 0.9 i n . CHONETES,

p e d i c le view

b ra c h i a l v i ew

COM POS I T A , M i ssi s s i p p i a n to P e r m i a n , is s u b - c i r c u l a r i n o u t l i n e a n d c o n vex i n profile. T he s h e l l i s fa i r l y s m o oth w ith fi n e g r o wth l i n es. Ped i c le valve h a s a s u l c u s . M ax i m u m l e n g th about 1 i n .

p rofi l e

P e n n sy l v a n i a n to P e r m i a n , has a s h e l l w h i c h is s e m i c i r c u l a r i n o utl i n e , with a stra i g ht h i n g e . Beak is p r o m i n e n t ; p e d i c l e

JURE S A NIA,

valve stro n g l y c o n vex ; brachial valve con cave. Spines o r s p i n e scars are found o n both valves. M ax i m u m l e n g t h about 1 . 5 i n .

BRACH IOPODS M A RG t N I FE R A , M i s s . - P e r m . , is a s m a l l s h e l l with a w i d e h i n g e . ,Pedi cle valve stro n g l y c o n vex ; b rac h i a l v a l v e c o n cave. M e d i u m r i b s . S h e l l may h a v e s o m e s p i nes a n d a p r o m i n e nt s u l c u s . Length 0.5 to 1 i n . L I N OPR O DUCTUS, M i s s . - P e r m . Very l o n g ped i c l e valve, often wri n k led near the h i n ge and stro n g l y c u rved near t h e bea k ; flatte r at front. R i b s are p r o m i n ent and s i n u o us. S p i n es may be present. Length about 1 in.

P e n n sy l v a n i a n to P e r m i a n . A s m a l l s h e l l , g l o b u lar i n outl i n e a n d i n p ro fi l e . T h e s u rface of the s h e l l i s wavy with very fi n e r i b s s u p e r i m p o s.e d . Other feat u res are i nterna l . Length a b o u t 0.5 i n .

E N TELETES,

R H YNCH ONELLA i s t h e overall

n a m e ·for a group of c o m m o n brach i o po d s ( r h y n c h o n e l l i d s ) of t r i a n g u l a r outlin e a n d with a s h o rt h i n g e. Most i n the g r o u p have a c o n vex p ro fi l e and stro n g r i b s a n d a s u l c u s . Length 0.5 to 1 .5 in. Ordovician to Recent.

p e d i c l e view

p rofi l e

p ro fi l e

p rofi le

b r a c h i a l v i ew

A N N E L I D S (above) a n d related w o r m s a re u n c o m m o n foss i l s . T h ey p l ay an i m po rtant part i n g e o l o g ical p roc esses by pass i n g sand and soil t h ro u g h t h e i r a l i m entary tracts. Fos s i l worm b o ri n g s , casti n g s , a n d tra i l s are fo u n d . M i n ute jaw p i eces (scolecodo nts) o f m a r i n e w o r m s are c o m m o n m i c rofo s s i l s . Some m a r i n e worms sec rete l i m y tu bes w h i c h m ay beco me fo s s i l s , a n d t h e c o n i cal a n d pyra m i d a l foss i l s , Tentaculites a n d Con ularia, m ay rep re sent rem a i n s of worm - l i ke a n i ma l s . Worms a re fo u n d i n rocks from P re-Ca m b ri a n t o Recent. - =- ·� - •· )

. . ' ,/

::IF...

..- ·

S C O LE CODO N T S , O rd o v i c i a n to

Recent, a re m i n ute c h i t i n o u s fo s s i l s, representi n g t h e jaw parts of ma rine a n n e l i d worms. H ig h ly m a g n ified. C O N U LARIA, length to 6 i n ., O rdo

v i c i a n to J u rass ic and TEN TACUL ITES, l e n gth to 2 i n . , O ra o v i c i a n to

Devo n i a n , a re o bs c u re ext i n ct f o r m s ; possibly worms.

SER P U LA, S i l u rian to Recent, i r r e g u l a r calcareo u s t u bes, s h own h e re on a b rac h i o pod, a re secreted by s m a l l w o r m s . Length to 0.2 i n . W ORM BORINGS a re somet i m es f o u n d in s e d i m e n tary rocks. O ften t h ey are p e r p e n d i c u la r to the bed d i ng of the rocks. B o r i n g s a re a l so made by m o l l u sk s .

A RT H R O P O D S a re a g reat a n d s u ccessfu l p h y l u m of

i n verteb rates . They have seg me nted bod i es and pai re d , j o i nted l i m b s , a h a rd exte rnal coveri n g , with fl ex i b l e j o i nts, a n d wel l-develo ped ci rc u l atory, nervo u s , d i gestive and re p ro d uctive syste m s . Seven g ro u ps of a rt h ro p o d s (sp i ders, ticks, m i l l i pedes a n d centipedes, l o bste rs, cra bs, bar nacles, i n sects) i nc l u d e over a m i l l i o n s pecies of g reat d i vers ity. T h i s tremen d o u s p h y l u m is vari o u s l y d i v i ded b y experts i nto classes -the fo u r most i m p o rtant of w h ic h are below. A RT H R O P O D S I M PORT A N T AS FOSS I LS TRILOBITES ( p p . 94-97) , C a m b r i a n to Per

m i a n , a re c o m m o n th ree- l abed m a r i ne a rt h ro p o d s , c o n s p i c u o u s l y seg mented , and have th ree body d iv i s i o n s . Le ngth Y. to 27 in. See p . 74 for names of external parts. CRUSTACEA N S (pp. 98- 1 00), Camb rian to

Recent. C o m m o n , mostly aq uatic with two pai rs of anten nae and u s u a l l y several pai rs of two- b ra n c h ed a p p e n d a g es . I nc l u d es crabs, l o b sters, s h r i m ps and ostracod s . CHELICERATES ( p p . 1 01 - 1 02), Cam b rian

to Recent. Lack anten nae. A p pe n d ages may be m o d ified to form p i n cers. The g r o u p i n c l u d es a i r b reat h e rs ( s c o r p i o n s , m ites, ticks a n d · s p i d ers) a n d water b reat h e rs (euryp terids). IN SECTS (p. 1 03), Devonian to Recent.

W i n g e d a rt h ro p o d s , g en e ra l l y with 3 pai rs of w a l k i n g l e g s . T h e most n u merous arth ro pods both i n k i n d s and i n d i v i d uals. T h rive o n l a n d a n d i n fresh water.

T R I L O B I TES , Ca m b rian to Perm i a n , are ext i n ct m a r i n e

a rth ropods o f g reat d i versity a n a i m po rta nce as Paleo zo i c g u i de fos s i l s . T h e b o d y h a s th ree m aj o r d i v i s i o n s a n d the t h o rax has th ree l o bed seg me nts (see p . 74 for deta i l s of structu re) . T h ey were p ro ba b l y b ottom-feed i n g scave n g ers and p redato rs. CAM B R I A N T R I L O B I T E S

� OLENELLUS,

Lower C a m b rian. A tri l o b ite with semi-circular c e p h a lo n , large c rescent-shaped eyes a n d a long, seg me nted g l a b e l la. The l o n g t h o rax had many segm ents ; fi rst 15 normal, t h e rest narro w ; some w ith s p i ne s . Len gth 9 i n .

.....

AGNOSTUS, Cambrian. M i nute c e p h

a l o n and pygid i u m s i m i l a r in s i z e ; no eyes ; tho rax of two seg me nts. L e n gth about 0.2 i n . Lower C a m b rian from maritime Canada and W . E u rope, has an oval outl i n e ; s e m i - c i r c u l a r cephalo n , l o n g a n d narrow g labella, w i t h l o n g s p i ne. C rescent-s haped eyes. Very s m a l l py g i d i u m . Maximum l e n g t h a b o ut 6 i n . CAL L A V IA,

�

ELRATHIA, M i d d l e C a m b r ian, h a s a n

oval outl i n e ; sem i- c i rc u la r cephalon with broad , b l u nt, s h o rt g la b e l l a ; pyg i d i u m flat, sem i- c irc ular w i t h a s mooth m a r g i n . Length 1 t o 2.5 i n .

OGYGOPSIS, M i d d le Cambrian, a Cor-

d i l leran form, has a large cephalon a n d pyg i d i u m , s e m i - c i r c u l a r i n o u t l i n e , a n d s m a l l eyes. G rooved t h o racic segments. Pyg i d i u m segme ntati o n is c o n s p i c u o u s . Max i m u m l e n g t h about 3 i n .

�

......

M i d d le C a m b r i a n , has a b r o a d , s e m i - c i r c u l a r c e p h a l o n w i t h tape r i n g g la b e l l a ; e y e s s m a l l . Body n a r rows posteriorly. Length about 3.5 in . PTYCHOPARIA,

......

EODISCUS, Lower a n d M i d d l e Cam

b r i a n , m i n ute, s i m i lar to Agnostus, but with s h o rt g l a b e l l a and neck spine a n d d i s t i n ctive pygid i u m . Length a b o ut 0 . 3 i n . CO NOCORYPHE, M i d d l e C a m b r i a n o f

�

eastern N. America a n d E u rope, is s u per fi c i a l l y s i m i l ar to Ptychoparia but has no eye s ; 1 4 or 15 t h o racic segm ents ; s m a l l a n d s mooth pyg i d i u m . The g l abella i s s h o rt a n d tapered . Len gth a b o u t 2 i n . PARADOXIDES, Middle Cam

M i d d l e C a m b rian of W . N o rt h A m e rica, has the g l a b e l la fu rrowed ; crescent- s h a ped eyes ; 7 to 9 t h o racic s e g m ents ; s e m i - c i rcu lar, well seg m e nted pyg i d i u m . Length about 1 . 5 in. BATHYURISCUS,

brian, is large with s e m i - c i r c u l a r cephalon a n d forwardly expand ing g labella. It has h eavy t h o racic s e g m ents and a small p yg i d i u m . Length 1 0 i n .

LO W E R A N D M I D D L E DAL MANITES, S i l u rian to Lower

DIKELOCE PHALUS, U p per Cam

Devo n i a n . G l a b e l la expanded a n d furrowed. E y e s a re l a r g e , rai s e d , w i t h many facets. 1 1 g rooved, s p i ned thoracic segments. Maximum l e n gt h a b o u t 6 i n . ; u s u a l l y about 3 i n .

b r i a n , has a b road c e p h a l o n with a w i d e b r i m a n d s h o rt, b l unt, f u r rowed g l a b e l l a ; 1 2 t h oracic seg ments ; pyg i d i um with two spi nes. Max i m u m l e ngth about 6 i n .

FLE X ICAL Y MENE, Ordovician to S i l u ri a n , is s i m i l a r to Calym en e b ut w ith a l i p-l i ke pre-g l a b e l la m a rg i n . C o m m o n i n E u rope a n d N orth A m e r ica. Max i m um l e n gth a bout 2 in.

TRINUCLEUS, Ordovician - a g ro u p of t r i l ob ites. Large c e p h a l o n with b r o a d pitted border a n d an i n flated g l a b e l la. N o e y e s . L e n g t h 1 i n .

a n t e r i o r a n d d o rsal v i ews of e n ro l l ed specimen

S i l u ri a n t o M i d d l e Devo n i a n , is a s m ooth t r i l o bite w ith a f u rrowed g l a b e l l a ; 13 g rooved t h o racic s e g m ents ; pyg i d i u m s e m i c i rc u lar. L e n gt h 1 .5 to 3 i n .

CAL YMENE,

P A L EOZO I C T R I LO B I T E S BUMASTUS, O r d o v i c i a n t o S i l u r i a n , has a n o v a l o u tl i n e ; w i d e axial lobe. G l o b u la r c e p h a l o n a n d pyg i d i u m l a c k seg m e n tat i o n . K i d n ey s haped eyes. M a x i m u m l e n g t h about 4 in.

ISOTE LUS, Ordovi c i a n , has both

A S A P H U S , O rd o v i c i a n ( a n " e n r o l l e d " spec i m e n ) , has a large s e m i c i r c u l a r c e p h a l o n a n d i n d i st i n ct g la bella ; 8 t h o racic segme nts, g rooved but b l unt. B road axis. Length a bo ut

P HACO P S , S i l u ri a n to Devo n i a n , h a s a s e m i - c i r c u l a r c e p h a l o n with rou n d e d c o r n e rs a n d i nflated g l a bella. I t has 1 1 g rooved t h o racic s eg m ents. Len gth u s ua l l y 2 to 3 in.

c e p h a l o n a n d pyg i d i u m s m ooth a n d s u b-tria n g u lar i n s h a p e ; g l a b e l l a b l unt and u n fu rrowed. T h oracic seg m e nts with wide axis. Length a b o ut 4 i n . ; a few f o r m s m u c h larger.

M i ss i s s i p p i a n , has a n o v a l , s m ooth outl i n e ; g l a b e l l a e x p a n d e d forward a n d f u r rowed. Eyes s m a l l ; 9 t h oracic seg ments. Pyg i d i u m with 13 to 1 6 seg m ents. Length t o 2 i n .

GRIF F I THIDES,

N ote the large, ra i sed m u lti-faceted eyes.

C R U ST A C E A N S are a maj o r g ro u p of mari n e, f resh足 wate r, a n d l a n d a rt h ro p o d s . M a r i n e forms, m ost c o m m o n a n d i m p o rtant today, i n c l u d e crabs, l o b sters, s h r i m ps a n d barnacles. C rayfis h l i ve i n fresh wate r ; s o w b u g s o n l a n d . C r u stacea n s d eve l o p t h ro u g h several l a rval stages, m o lt足 i n g t h e i r s h e l l s as they g row. A l l h ave two pai rs of a nte n 足 nae ; most b reat h e t h ro u g h g i l l s . Ostracods are i m po rta nt foss i l cru stacea n s .

Lower S i l u ri a n to U p per Devo n i a n . La rge, o b l o n g s h e l l ; stra i g ht, s h o rt h i n g e ; valves u ne q u a l . L e n gth a bout 0.4 i n .

LEPERDITIA,

DREPA N ELLA, M i d d l e Ordovician to Lower S i l u ri a n . Stra i g ht h i n g e ; l o n g marg i n a l rid g e a n d two o r more i s o lated lobes. L e n gth 0.1 i n .

OST RA C O D S a re s m a l l , b i val ved c r u stacea n s a b u n 足 d a n t i n ocea n s b u t a l s o l i v i n g i n fresh wate r. T h e a n i ma l o cc u p ies a late ra l ly c o m p ressed s h e l l , h i n ged a l o n g t h e u p per marg i n . O n e v a l v e ofte n o v e r l a p s the o t h e r . S h e l l s have lobes, p its, s p i n es a n d r i b s . Ostracods m o lt a s they g row, and i m m at u re m o l t stages often occ u r as foss i l s . Becau se t h ey a re co m m o n , ostracods a re w i d e l y u s ed i n correlat i o n o f strata of C a m b r i a n to Recent A g e . L I V I N G OSTRACOD

FOSS I L O S T R A C O D

FOSS I L OSTRACODS DIZYGOPLEURA, S i l u rian t o Devo n i a n . Has a s u b-oval outl i n e ; f o u r stro n g vertical l o b e s , the i n n er ones conti n u o u s ventra l l y . T h e left valve overlaps t h e rig ht. Len gth 0.04 i n .

BOLLIA, O r d o v i c i a n t o Devo n i a n , u s u a l l y has a swo l l e n , l o n g o uter r i d g e, wit h i n w h i c h is a para l l e l central, h o rse shoe r i d g e . The s u rface i s g e n e r a l l y p itted . Le ngth 0.04 i n .

KIR K B YEL LA, M i d d l e S i l u r ian t o P e n n sylva n i a n . A n e q u i valved ostracod with a central, d o rs a l , n otc h - l i ke s u l c u s . It i s s u b-oval to f o u r-s i d ed i n outl i n e ; s u rface netted or p itted . Length 0.04 i n .

M i ss i s s i p p i a n to P e r m i a n . Has a s u b-oval o u t l i n e with stra i g ht h i n g e . Valves u n e q u a l with right overl a p p i n g l eft ; median pit a n d p r o m i nent h o ri z ontal r i b s . Length 0.04 i n .

G L Y P T O PLEURA,

C YTHEREIS, C retaceous. F r o n t e n d i s deep ; b a c k e n d is c o m p ressed a n d ro u n d e d . V a l v e s a re u n e q u a l ; top a n d bottom m a rg i n s stra i g ht. O r n a ment of a variable a m o u nt. C o m p l ex h i n g e struc ture. Length 0.03 i n .

CYTHEREL LOIDEA, J u rassic t o Re

cent, has a s u b-oval o u t l i n e with a stra i g ht h i n ge. O r n a m e n t variable, but u s u a l ly a few stro n g , h o r i z o ntal r i d g es . Len gth 0.03 i n .

B A L A N US, Eocene to Recent. The acorn barnacle h as a pyra m i dal足 s h aped s h e l l , made of six fixed a n d t w o s m a l l movable plates. G r o w s at t i d e level on ro cks. Maxi m u m h e i g ht a b o ut 2 i n . ; often s m a l ler.

GOOSENECK B A R N ACLES are atta c h ed by l o n g stalks. P l ates a re s i m i l a r to t h o se of acorn barnacles, but a re larger, thin, a n d smooth. May be a more p r i m itive form.

B A R N A C L E S a re u n u s u al c r u stacea n s . F ree-sw i m m i n g l a rvae settle h ead down a n d g row overl a p p i n g l i my p l ates. The a n i m a l feed s with its frin ged feet. Foss i l s n ot com足 m o n th o u g h known from early Paleozo i c. Some paras itic fo rms lack a s h e l l . S H R I M P S , C R A B S , A N D L O B S T E R S are re lated to sow b u g s , c rayfis h and many oth er fo rms. A l l m o lt a n d s hed th.e i r s h e l l s as they g row. A n i m po rtant g ro u p today b u t l e s s co m m o n as fos s i l s . AEGER, J u ra s s i c, is s h ri m p - l i ke with a latera l l y co m p ressed body and a p roject i n g "beak." D i st i n ctive l i m bs and a long a b d o m e n . M a x i m u m l e n g t h a bo u t 6 i n .

1 00

J u rassic, is a s m a l l l o b ster-like d e c a p o d with a very b road carapace, about e q u a l i n length to t h e a b d o m e n . Length a b o ut 4 in.

ER Y O N ,

E U R Y PT E R I D S , m ost c l osely related to h o rseshoe crabs, are fo u n d fro m the O r d o v i c i a n to the Perm i a n . Mo st c o m m o n i n the O r d o v i c i a n and S i l u ri a n , s o m e g rew 9 ft. l o n g to become the l a rg est Paleoz o i c a rt h ro po d s . T h e i r fl atte n e d , seg m e nted bod ies were cove red with c h iti n . The cep h a l o t h o rax (fused h ead a n d t h o rax) had two pai rs of eyes and six pai rs of a p p e n dages - o n e pai r of p i n cers, fo u r pai rs of walki n g legs a n d o n e oar- l i ke pai r. Beh i n d the c e p h a l ot h o rax came tw elve tape r i n g s e g m e nts u s u a l l y e n d i n g i n a s p i ke. Eu rypte r i d s were powerf u l sw i m m ers o f b rackish wate rs. They were p ro ba b l y ca r n i v o ro u s , feed i n g o n s m a l l e r i n verteb rates. STYLONURUS , S i l u rian t o D e足

v o n i a n , has p r o m i nent, central ey.es a n d g reatly e l o n g ated a ppendage&. The head ( p roso ma) is a n g u lar to s e m i -oval i n o u tl i n e a n d the s l e n d e r tape r i n g b o dy has a l o n g , poi nted ta i l . Length about 8 i n .

Ordovician to Permian. H a s a s e m i - c i rc u lar head a n d widely spaced c o m p o u n d eyes. B l u ntly ro u n d ed body outl i n e ; ap足 p e n d ages s h o rt, t h e last p a i r largest a n d pi ncer-l i ke. B l a d e-l i ke ta i l. Length a b o u t 3 i n . HUGHMILLERIA,

101

A R A C H N I D S A N D M Y R I A PO D S a re h i g h ly d evel o ped g r o u p s of a rt h ro p o d s common now b ut n ot as fos sils. Centi pedes a n d m i l l i pedes are myriapo d s . A rac h n i d s a re re lated t o eu rypte rids a n d i n c l u d e s p i ders, daddy- l o n g l e g s , a n d s c o rp i o n s . Scorp i o n s a re s m a l l ( 2 t o 8 i n . ) , seg mented l a n d an i ma l s w ith five pa i rs o f a p pendages ; t h e f r o n t pai r a re p i n cers, the rest a re wal k i n g legs. They have a l o n g , j o i n.ted ta i l . Foss i l s o cc u r from t h e S i l u rian , b u t i t i s n ot certa i n if the o l dest were air b reathers. S p i ders have o n ly e i g ht l egs. M o st h ave e i g ht eyes and poison fa n g s to para l yze their p rey. T h e body i s d iv i d e d i nto a ce p h a l ot h o rax a n d a b d o m e n . A l l l i v i n g fo rms have s p i n nerets, b ut n ot all make webs. Foss i l forms occ u r from t h e Devo n ia n t o Recent. ARC HITAR BUS, P e n n sy l v a n i a n , is an archaic s p i d e r ; a m e m b e r of a g r o u p with broadly j o i ned cepha lot h o rax a n d s h o rtened a b d o m e n . Carapace s h a p e i s d i s t i n ctive. Length about 3 to 4 i n .

PALAEOPHONUS, from t h e S i

l u ri a n , i s a p r i m itive s c o r p i o n , w i t h c h a racteristic s h ort, w i d e a p p e n d a g e s . It m a y h a v e been an a q uatic form rat h e r· than terrestria l . Length 1 .5 to 2 i n .

ACANTHERPESTES, P e n n s y l va n i a n , i s a giant m i l l i pe d e with s h o rt d i v i d e d legs. T h e e n t i re g ro u p i s conservative a n d has c h a n g e d very l ittle. Max i m u m length about 8 i n .

1 02

I N S E C T S , t h e larg est g ro u p of a rt h ro p o d s , co m p rise a b o ut th ree-q u a rters of a l l l iv i n g a n i ma l s - over 900 , 000 species a re k n o w n . Some a re e n o r m o u s l y a b u n dant a n d p l a y an i m p o rta nt ro l e i n h u m a n affa i rs . I n sects a r e ada pted to many d ifferent e n v i ro n m ents a n d are s u ccessfu l i n most o f t h e m . They h ave a d i st i n ct h ead, th o rax a n d abdo足 m e n , o n e pa i r of anten nae, th ree pai rs of l e g s , a n d o n e or two pai rs of w i n g s . Some are w i n g less. I n sects a re rare as fos s i l s . The o l dest a re w i n g less fo rms fro m t h e Devo n i a n . In P e n n sylva n i a n ti mes ( A g e o f I n sects) s o m e i n sects g rew to g ia nt p r o p o rtio n s a n d m o re than 4 00 s pecies a re k n o w n . Ma n y l i v i n g i n sects s h ow l ittl e c h a n g e from a n c i ent fo rms in the l ate Paleoz o i c . Mesoz o i c s p e c i e s a re m o re c o m m o n ; o v e r a t h o u sa n d have been desc r i b e d . a lace足 wing from the J u ra s s i c . Lacew i n g s ( n e u ropte r i d s ) , w h i c h a re d i sti n 足 g u i s h ed by t h e i r ti n e w i n g venati o n , ra n g e f r o m P e r m i a n t o Recent. Length about 1 i n . MESOPSYCHOPSIS,

COC KROACHES ( b l atto i d s ) are

an ancient and w i d e s p read g r o u p ( P e n n sylvanian to Recent). S o m e w e r e u p to 4 i n . l o n g . 800 U p p e r P a l e o z o i c species a r e k n o w n .

a J u rassic dra g o n fly wit h a wi n g s pan of about 2 i n . O utstretc hed wings a re typical of the group, which o c c u rs from Permian to Recent.

TARSOPHLEBIA,

1 . CRINOID 2. A S T E RO I D 3 . O P H I U RO I D 4 . H O L OTH U R I O I D

5. ECH I N O I D 6. E D R I OA S T E RO I D 7. C YSTO I D 8. B L A ST O I D

L i v i n g e c h i n o d e r m s ( 1 - 5 ) . F o s s i l fo r m s (6-8) .

ECH I N O D E R M S are a ph y l u m of m a r i n e a n i mals cov足 ered with l i my p l ates o r s p i n es. Plates a re fixed in sea u rc h i n s (ec h i n o i d s) , fl ex i b l e i n some starfi s h (aste ro i d s ) , a n d i so lated i n sea c u c u m be rs ( h o l ot h u r i o i d s ) . E d r i oas足 tero i d s , cysto i d s , b lasto i d s and c r i n o i d s l i ved attac hed ; the rest are free mov i n g . Th i s p h y l u m co n s i sts of e i g ht c o m m o n c l a sses i l l u strated above. Below are ty p i cal i nternal str u ct u res. D i g est ive system i s g reen ; water足 vas c u lar system o ra n g e . Exoskeleton is p u r p l e . These an i mals also have a wel l -deve l o ped n e rvo u s syste m .

BLA STOI D

1 04

tooth

E D R I O A S T E RO I DS a re ext i n ct, attached ec h i n oderms w ith ro u n d o r fl atte ned, often a sy m m etrical b o d ies cov ered with s m a l l , i r reg u lar, fl e x i b l e p l ates. Each h ad a cen tral m o uth s u rro u n d ed by five s l e n d e r, s i n u o u s , attac h ed arms. C a m b rian to M i s s i ss i p p i a n . CYSTO I D S , a n other exti n ct g ro u p o f ec h i n o d e r m s , a l so

had ro u n ded b o d i e s made u p of many i r reg u l a r p l ates with tria n g u l a r p o re o p e n i n g s . They lacked the s i n u o u s arms o f t h e e d r i oastero i d s . O r d o v i c i a n t o Devo n i a n . Ordovi cian. A g l o b ose cysto i d of m a n y i r r e g u l a r p o l y g o n a l p l a t e s . Central with s h o rt a m b u lacral mouth g rooves. Pyram i d a l a n a l covering near mouth. B o u n d aries between p lates often i n d isti nct. D i a m eter 1 to 2 in. ECHIN O S P HAERITES,

CARYOCRINITES, O r d o v i c i a n to

S i l u r ian, a cysto i d , with a g l ob u lar body of large, regu larly arra n g ed p l ates. M o uth and a m b u l acral g rooves co n cealed b e l ow plates. 6-13 feeble arms. P y ra m idal anal p l ates ; l o n g ste m . D ia m eter a b o ut 1 i n . D e v o n i a n to Mississippian. An e d r i oaste roid with five narrow, s i n u o u s a m b u lacral g rooves ; t h ree c u rved r i g h t , t w o left. Peri p h e ry has p ro m i n e nt r i n g s of s m a l l p lates. D i a m eter a b o ut 1 .5 i n . AGE LACRIN ITE S ,

O r d o v i c i a n to Devon ia n . An e d rioastero i d with a t h i n , flatte n ed body a n d five s h o rt, radiating a r m s , s u r ro u n d ed by a r i n g of large p l ates a n d marg i n al r i n g s of s ma l ler o n es . D i a m eter about 0.8 i n . HEMICYSTITE S ,

1 05

B L A STO I DS (Ordov i c i a n to Per m i a n ) , an ext i n ct c lass .

of ec h i n o d erms, a re especial l y c o m m o n i n M i s s i s s i p p ian rocks. The fos s i l s c o n s i st of a X- to 1 - i n . , c u p l i ke body w h i c h was atta c h ed at the base to a s h o rt ste m . Each "cup" h as 1 3 plates, sym metrica l ly arra n g ed , with five peta l-s h aped am b u lacral g rooves. The l i v i n g a n i mal g rew i n s i d e t h e c u p as s h ow n o n pages 74 a n d 1 04. sj d e

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CODA STER, S i l . t o P e n n . , h a s a

pyra m i d a l c u p , s ha rply poi nted be足 low and five-sided i n c ross secti o n . P l ates a ro u n d base a n d on the s ides a re l o n g ; t h o se near mouth a re s h o rt. A m b u lacra l g rooves a re s h o rt and trian g u l a r. H e i g h t 0 . 5 to 1 i n . PE N TREMITES, M i s s . t o P e n n . ,

has a s m a l l , b u d - l i ke c u p w i t h s m a l l basal plates a n d very l o n g s i d e plates a r o u n d t h e b road a n d petal足 l i ke a m b u l a c ral g rooves. C o m m o n i n M i ss i s s i ppi V a l ley. H e i g h t a bo ut 1 to 2 i n .

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from the M i s s i s s i p p i a n , has g l o b u la r cup with very l o n g a m b u l a c ral g rooves which lack pores o n o uter edg es. Plates along the sides a re large and overlap those a r o u n d t h e mouth. H e i g ht about 0.5 i n .

CRYPT O B L A STUS,

SCHIZ O B L A STUS, M i s s i s s i p足 p i a n to P e r m i a n , has an ovoid c u p. Plates a r o u n d mouth are l a rge, with p ro m i nent pai rs of o p e n i n g s near the top. Base i s usually d e p ressed. A m b u lacral g rooves a re l o n g a n d n a rrow. H e i g ht 0 . 8 i n .

side

1 06

radial p l ates

C R I N O I D S , o r sea l i l ies, are flower- l i ke ec h i n o d e r m s , often beautif u l l y c o l o red, w h i c h g row i n c o l o n ies o n t h e sea fl o o r. Some foss i l f o r m s were free swi m m i n g b ut most were fi xed by a stem formed of va r i o u s l y s h aped d i scs o r c o l u m n a l s ( p . 74) s u r m o u nted by a c i rclet of a r m s . A l l have a fi ve-f o l d rad ial s y m m etry, but vary i n s h a pe, p l ates a n d a r m s . O rdovrc i a n to Recent.

has a d e e p c u p , c o m posed of a f e w p l ates, often with a rou g h s u rface. The l o n g a r m s are b ra n c h e d . M i s s i s s i p p i a n to Per m i a n . M a x i m u m h e i g h t of crown of t h i s c r i n oid about 2.8 i n . , but it is often smaller.

PLATYCRINITES

T r i a s s i c - Tertiary, and the s i m i l a r Pentac r i n ites, have long, b ra n c h ed arms a n d star shaped c o l u m n a l s . Both of these stem-bea r i n g , arti c u late c r i n o i d s a re c h a racte rized by a l a r g e crown a n d a s m a l l d o rsal c u p . Crown to 2.5 i n .

ISOCR I N US,

GL YPTOCRI N U S , Ordov i c i a n to

S i l u ri a n . The c u p of t h i s c r i n o i d w i t h i t s star- s h aped o r n a m e n t i s small in comparison with rest of crown. T h e a r m s are l o n g , s l e n d e r and b ra n c h i n g . M a x i m u m h e i g ht of c rown 2.5 i n . TAXOCRINUS, D e v o n i a n t o M i s

s i s s i p p i a n , has a s m a l l cup s u r m o u nted by m a s s ive, b ra n c h i n g , e m b ra c i n g a r m s . T h e d i s c - l i ke plates of the stem of t h i s and s i m i l ar forms are the most c o m m o n c r i n o i d fos s i ls. H e i g ht of crown about 2 i n .

IS shaped co l u m na l s

STA R F I S H a n d B R ITTLE S T A R S ( A stero i d s a n d O p h i u ro i d s) a r e free- m o v i n g ech i n oderm s . Sta rfis h have five b road arms with t u b e-feet a l o n g the g rooves o n t h e i r lower s u rface. B rittle stars have a wel l-defined ce ntral d i sc a n d s l ender a rms fo rmed of d i screte "verte b rae " . Both g r o u p s a r e rare as fos s i ls. HUDSONASTER, M i d d l e t o U p

per O r d o v i c i a n , is an early starfish with t h i c k, s h o rt, ta pering arms cov ered with large, reg u larly arranged p lates. It has p r o m i n ent a m b u lacral g rooves on the lower s u rface. D i a m eter a b o ut 1 i n .

( D E V O N A ST E R) is an O r d o v i c i a n - D ev o n ian starfi sh with sharply poi nted arms and reg u lar radiat i n g o rn a ment on the u p p e r s u rface. It has a central d i sc with many s m a l l plates. A m bu lacral g rooves p r o m i nent. D i a m eter about 1 . 5 i n . MESOPALAEASTER

URASTERELLA i s an O rd o v i c i a n t o Pen n sy l v a n i a n sta rfi s h with l o n g , s l e n d er, fl e x i b l e a r m s but with no o b v i o u s central d i s c . It has promi n e n t a m b u la c ra l g rooves on the lower s u rface a n d small, i rreg u l a r p l ates. D i a m eter about 2 i n .

AG A NASTER is a M i s s i s s i p p ian brittle star with a l a rge, flower- l i ke central d i s c a n d s h o rt, s l e n d e r arms. Brittle sta rs d eveloped i n the Ordo v i c i a n but were not common u ntil the Mesozoic. Often represe nted by i s o lated arm p l ates. D i a m . a bout 1 i n .

E C H I N O I D S (sea u rch i n s, sand d o l l a rs a n d their ki n ) h a v e s p i n y , g l o b u lar, fl attened o r h ea rt- s h a ped s h e l l s o r tests made of smal l , limy p l ates. The test often has fi ve fo l d rad i a l s y m m etry. A l l Paleozoic echi n o i d s (as Lovene chin us) were reg u l a r ; m a n y later forms (as Micraster ) a re irreg u l a r . Fo u n d from the O rd o vici a n to Rece nt. LOVENECHI N U S, M i ss i s s i p p i a n ,

h a s a large s p heri cal test, w ith l o n g , a m b u l ac ral a reas, e a c h m a d e of f o u r c o l u m ns of s m a l l plates. Be tween the g rooves are four to seven c o l u m n s of l a rger p l ates. D i a m eter 3 to 4 i n .

CIDARIS , U p per Triassic t o Re

cent, i s a g r o u p name for ech i n o i d • w i t h a r o u n d test a n d m o u t h a n d a n u s a t o p p o s ite p o l e s . A m b u l a c ra l o n g a n d narrow ; the s paces be tween are broad, with large tubercles a nd spines. Maximum d ia m eter about 3 i n .

CLY PEUS, J u ra s s i c , i s a n i rreg

u l a r s a n d d o l l a r with flattened test a n d a c i rc u l a r o r five-sided o u t l i n e bearing peta l - l i ke a m b u lacral a reas. T h e m o uth is at the c e ntral point of the test w h ic h is covered by v e ry s m a l l t u b e r c l es. D i a m . to 4 i n .

MICRASTER, C retaceous t o M i o cene , has a t h i c k, heart-sha ped test. The a m b u l acral a reas are s u nken and the spaces b etween a re fi l led w ith large p l ates. T h e m o uth is near the ante r i o r border. S u rface a ran u lar. Length about 2 i n .

1 09

= d i gestive tract F = foot

M O L L U S KS i ncl u d e five c l asses o f si m i lar struct u re but d ifferent exte rn a l a p pearance, as s h ow n ab ove. Mo l l u s ks are an o l d and s uccessf u l g rou p ; most a re mari ne, m any fre s h -wate r, a n d s o me l i ve o n l a n d . A few a q uatic fo rms a re free float i n g o r free s w i m m i n g but the maj o rity a re b otto m dw el l ers i n sand or m ud . Some b u rrow i nto rocks o r t i m bers. A b o ut 150,000 l iv i n g s peci es a n d th o u sa n d s o f fos s i l f o r m s h ave b e e n d escri bed . Mo l l u sks ra n g e i n s i ze f r o m 60-ft. G i a nt S q u i d s a n d Tridacn a c l a m s weig h i ng over 500 p o u n d s down to a l m ost m icrosco p i c s pec ies. S h e l l structu re va ries from the c o i l ed fo rm of s n a i ls to the sy m m etrical b i va l ves of clams and the ei g ht p lates of chitons. Two l i v i n g classes , the pelecy p o d s (c l a m s , oys足 ters, m u ssels) a n d gastro pods (w h e l ks, s n a i l s , l i m pets ) , are a b u n dant. Fo s s i l s of th ese g ro u ps and ce p h a l o p o d s a re co m m o n b ut ch ito n s a n d tusk s h el l s are rare, th o u g h both occu r i n t h e ea rly Paleozo ic. Many m o l l u s ks are excel l e n t i n dex foss i l s . 1 10

G A S T R O P O D S have a b road , m u s c u l ar foot, a w e l l deve l o ped h ead with eyes, m o u t h , a n d ten tac l es. S o m e have a file- l i ke to n g u e ( rad u l a) w h ic h c a n b o re t h ro u g h t h e s h e l l s o f other m o l l u sks. Most gastro p o d s have l i my s p i ral s h el l s. Of over 50,000 s pecies, 35,000 a re l iv i n g . The shell o p e n i n g may be c l osed by a l i d ( o percu l u m) w h en the a n i m a l d raws i n . O n ce c o nfi n ed to sea s , l ater s n a i l s became adapted t o l ife i n p o n d s , i n stream s a n d o n l a n d . LO W E R P A LEOZO I C G A ST R O P O D S HYPSELOCONU S , U p per Cam-

b r i a n to Lower O r d o v i c i a n , is a p r i m itive gastro pod with a h i g h , con ical, u n co i l ed shell, the apex of which i s often off-center. Form variable. 0.7 i n . HOR MOTO MA, O r d o v i c i a n t o Si

l u ri a n , i s a w i d e l y d i stributed, h i g h spi red s h e l l , with w h o r l s ro u n ded a n d sepa rated by deep notches. A p e rt u re notched ; s u rface q u ite smooth. 2 to 2.5 i n .

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MACLUR I TES is a nea rly fl at O rd o v i c i a n gastropod w ith low but stro n g ly rounded w h o rls a n d a b road, deep cent ral d e p re s s i o n on t h e u pp e r s i d e . S u rface smooth. 2 to 3 in.

basal v i ew

P A L EOZO I C A N D BE L LEROPHO N , Ordovician to T r i a s s i c . A flatly c o i led gastropod with t h e outer whorl e m b ra c i n g e a r l i e r o n es. B r o a d a p e rt u r e , with s i n u s . S i m ple o r n a m ent. Max i m um d ia m eter about 2 i n . PLAT YCER A S , S i l u r i a n t o Per

mian. A loosely c o i led form often with i r reg u larities i n the s h e l l due to c e m e ntat i o n to other objects. S p i ral ..111111 or tra n sverse o r n a m e nt. Max i m u m ""'' d i a meter about 1 . 5 i n .

...

P L ATY OSTO M A , S i l u ri a n to De v o n i a n , i s a form of Platy ceras with a low- s p i red, g l o b u l a r s h e l l . Several w h o r l s , the last much t h e larg est, a re all i n contact. H e i g ht a b o ut 1 . 5 in .

WORT H E N I A, M i s s i s s i p p i an to P e r m i a n , has a w i d e , low-s p i red s h e l l . The outer l i p has a s h a l low s i n u s w h i c h becomes ti l led i n a ro u n d the who rls. Variable but well d evel o ped o r n a m e n t. H e i g ht a b o ut 1 .3 i n .

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STRAPAROLLUS

or Euompha

lus, S i l u r ian to P e r m i a n , is flatly c o n

ical o r n early fl a t with a b road c e n t ral d e p re s s i o n . W h o r l s a re ro u n d to trian g u l a r ; feeble o r n a m ent. D i a m eter about 2 i n .

M ESOZO I C G A STRO P O D S N ERIN EA, J u ra s s i c t o Cretac eous,

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is a h i g h - s p i re d , o ften s l e n d e r s h e l l . W h o r l s often c o n cave ; apertu re with s h o rt notch. Variable o r nament. Max i m u m height about 5 i n . MURCHISO N I A , S i l u rian t o Pe r m i a n , is a n ot h er h i g h - s p i red s h e l l , rat h e r l a rge, with w h o r l s r o u n d e d t o a n g u l a r . G rowth l i nes present. Outer lip with a s i n u s . H e i g h t f rom 1 to 2 i n . (far right). PLEUROTO M ARIA , J u rassic t o C retaceo u s , has an ac utely c o n i c a l s h e l l with a p r o m i n e nt s l it on outer lip a n d s i n u s fi l l ed i n o n w h o r l s . C o n s i d e ra b l e ornam ent. M ax i m u m h e i g h t a bout 2 . 5 i n . .....

CER I T HIUM is a g ro u p name for

�

J u rassic to Recent gastropods with h i g h - s p i red, m a n y - w h o rled s h e l l s , o ften t u r reted a n d w i t h c o n s i d e r a b l e o rname nt. M a x i m u m h e i g h t a bout 5 in. T U R R IT E L L A , C retaceo us to Re-

cent, is a g r o u p name for s l e n der, h i g h - s p i red shells with i n c i s ed s u tu res and w i t h s p i ra l o r transverse o rnament. S i m p l e a perture. Maxi m u m h e i g h t about 4 i n .

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cross sectio n

C E N OZO I C C ret. -Rec. A g r o u p of ac utely c o n i c a l , s h ort- s p i red s h e l l s . W h o r l s w i t h strai g ht s i d es. L o n g , n a rrow apertu re. M a x i m u m h e i g ht about 2 i n .

C O N U S,

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DE N T A L I U M , O r d o v i c i a n t o Re cent. A s c a p h o p o d ( p . 1 1 0) . T u s k s h a ped s h e l l , c u rv e d , t a p e r i n g , with b o th e n d s open. M a x i m u m l e n gth about 5 i n . ; u s u a l l y s m a l l er. P O L YGYRA, Paleocene to Recent. A l a n d s n a i l . T i g htly c o i led, l ow . s p i red s h e l l , flatte ned below. I n d ented aperture. M ax i m u m d iameter about 1 i n .

�

..,.

VOLUTA, Tertiary t o Recent. A g ro u p of moderately s p i red s h e l l s w ith a n g u l ated, ri bbed w h o r l s and n a rrow apertu re. M a x i m u m h e i about 4 i n .

F U S U S, C ret.-Rec. A g r o u p o f nar row, l o n g s h e l l s , with h i g h s p i re and r o u n d ed w h o r l s. Lo n g , na rrow a nte r i o r canal. Ornament va riable. Maxim u m h e i g ht about 2.5 i n . V I VIPAR U S , J u rassic t o Recent. A fre s h -water gastro pod with a l ow s p i red s h e l l . W h o rls are rou n d or flatte ned and the s utu res are in dented. Max i m u m h e i g ht a b o ut 1 . 5 i n .

1 14

�

GASTRO PODS PLA N O R B I S , J u rassic t o Recent. A g ro u p of fres h-water species. F latly coiled, with entire s p i re en c l osed i n body whorl. M ax i m u m d ia m eter a b o u t 0 . 9 i n .

VERT IGO, Eocene to Recent. Land

snail with b u l bo u s , oval outl i n e ; few s m ooth w h o rl s ; a p e rt u re con stricted. H e i g ht a b out 0.05 i n . NATICA, Triassic t o Recent. A g r o u p of low-s p i red forms, with large, b u l bo u s fi nal w h o r l ; s u rface g e n e ra l l y s mooth. M a x i m u m h e i g ht about 2 i n .

bottom view

side v i ew

CRE P I DULA, U pper C retac e o u s to R e c e n t . S l i p per s h el l s ; beak twisted ; a p e rt u re large, partly cov e red by a t h i n p l atfo rm. M a x i m u m l e n gth a bo ut 2 i n . ......

.....

Paleocene to Re cent, i s a thick, low- s p i red a n d o v o i d s h e l l with l a s t w h o r l larger than rest of s h e l l . S m ooth o r weak s p i ra l orna m ent. M ax i m u m h e i g ht about 1 in.

"L ITTOR I NA ,

115

P E LECY P O D S , " hatc h et-fo ot" or b i va l ved m o l l usks , a re mo st l y mari n e , b ut some l i ve i n fres h wate r. Oyste rs , m u ssels, a n d c l a m s are l i vi n g types. The two val ves of the shell, usually s i m i lar, are j o i n ed a l o n g a h i n g e line and a re h e l d together by teeth a n d m u scles, w h i c h leave im足 p ress i o n s o n the i n s i de of the shell. The c o m p ressed body of t h e a n i m al i s e n c l osed by the s h e l l . The s h e l l can o p e n to expose the foot a n d the s i p h o n s by w h i c h the a n i mal ta kes food a n d oxygen fro m the wate r. M o st p e l ecypo d s a re botto m dwel l e rs but some are active sw i m m ers. Oth e rs b u rrow in sand and m u d , s o m e a re b o rers a n d s o m e c e m e n t themselves t o fi x e d objects . Pel ecypod s (O rd o v i c i a n - Recent) a re c o m m o n foss i l s i n m a r i n e a n d some n o n-mari ne rocks. I n E u ro p e pelecy p o d s a re known as lame l l i b ra n c h s , o r p l ate-g i l led m o l l u s ks. I n oth er area s , al l p e l ecypods a re k n own as c l a m s , th o u g h s o m e types may b e called m u s sels, s c a l l o p s o r oysters.

B O D Y P L A N OF A CLAM

P A LEOZO I C P E L ECY P O D S CTE N OD O N TA h a s equ ivalved,

oval shells with s m ooth s u rfaces, sometimes with fi n e , concentric g rowth l i n es. N u m e rous s i mi lar teeth along h i n g e p l ate. O r d . - S i l . l e ngth about 1 i n .

�

.....

h a s a s harp, stee p l y i n c l i n ed beak n ear e n d of h i n g e ; u s u a l ly stro n g rad ial ribs. These e q u ivalved shells a re com mon i n U p per O rd o v i c i a n . Len gth a bout 1 i n . BYSSON YCHIA

has a p r o m i nent, b l u nte d , i n c u rved beak a n d a sub oval o u t l i ne. A d eep, o b l i q u e fold runs ac ross the valves. S i l u rian to M i ss i s s i p p i a n . M a x i m u m l e ngth about 2 i n .

G RA M M YSIA

PTERINEA h a s a w i d e h i n g e l i n e w h i c h exte n d s i nto "ears." Oppo site valves d i s s i m i lar a n d lack sym metry ; o r n a m ent of fine, c o n centric l i n es. It has two unequal m u scle scars. O rd . - Pe n n . M a x i m u m l e n gth about 1 . 5 i n .

G O NIO PHORA, S i i . - Dev. A l o p

sided s h e l l w ith p ro m i n e nt b e a k from w h i c h a r i d g e exte n d s to t h e r e a r marg i n . M ax i m u m l e n g t h a b o ut 2 in.

MODIOLO PSIS has a t h i n , oval s h e l l . A s y m m et r i cal valves a re c rossed by an o b l i q u e d e p res s i o n . O r d . - S i l . Two u n e q ua l m u s c l e scars. Max i m u m l e ngth a bo ut 1 .5 i n .

1 17

sil of d o ubtf u l affi n ities. Beak p rom i n ent ; h i n g e line long and stra ig ht. U ne q u a l t ri a n g u l ar valves have

stro n g rad i a l ri bs a n d often con cen tric g rowth l i nes. A nterior s h o rt with posterior o b l i q u e. Ordovician to Perm i a n . Length 1 to 2 i n .

MYALINA, Devo n ian to Permian,

DUNBARELLA a re flatte n e d , scal

has a poi nted, stro n g ly i n c l i n ed beak, and faint c o n centric ornamen tati o n . H i nge l i n e often promi nent. Length to 4 i n . ; u s ua l l y s m a l ler.

l o p-s haped shells, with fairly promi n e nt wings and bran c h i n g ribs. Feeble c o n c entric o r n a m ent. Penn sylva n ia n . Length 1 to 2 i n .

ALLORISMA, M i s s.-Perm., has an

CARBONICOLA h a s i ne q u i l ateral

e l o n gated , oval o u tl i n e . Marg i n is fl atte ned beh i n d t h e b l u nted, ante rior beak. Valves gape posteriorly. M ax i m u m l e n gth a bo ut 2.5 i n .

shaped, e l o ngated valves, oval in outline. A fresh-water g e n u s with h i gh, thick ante r i or. O rnament of conc entric g rowth l i n es. P e n n . Length 1 to 1 .5 i n .

CONOCARDIUM i s a stri k i n g fos

P A LEOZO I C A N D M ESOZO I C P E L E C Y PO D S 1 18

N UCULA is a " l t v m g fossi l , " s h ow

ing a l m ost no c h a n g e s i n ce S i l u rian times. S u rface c o m m o n ly has c o n centric g rowth l i nes. N u m erous small teeth and soc kets. M ax i m u m l ength about 1 .5 i n .

N , S i l u ri a n to P e r m i a n , has a stra i g ht h i n g e with p r o m i n ent wings a n d no teet h . Valves u n e q u a l , w i t h stro ng r i b s a n d s o m eti mes g rowth l i nes. Len gth about 1 i n .

L I MA is o b l i q u e l y oval i n outl i n e ; equ ivalved a n d i nfl ate d , with rad ial ribs. T h e p r o m i n ent beaks are pointed. Valves often gape. P e n n sylva n ia n to Recent. L e n g t h 3.5 i n .

PARALLELODO N , Devo n i a n to T e rt i a ry, is a n g u l a r in o u tl i n e, e l o n gate, with a l o n g , stra i g ht h i ng e l i n e. Has concentric g rowth l i nes. L e n gth about 1 .2 i n .

T R IG O N I A, J u r.-Rec., has a trian

PTE RIA, J u r. - R e c . , has t h i n , i n e q u i lateral s h a p ed v a l ves w ith a l o n g , stra i g ht h i n ge m e rg i ng i n t o l a rg e, u n equal w i n g s . F i n e c o n c e ntric or radial o r n a ment. Max i m u m l e ngth about 3 in.

g u la r o r c rescentic outl i n e . T h ick valves have a s h a rp r i d g e from the beak to the m a rg i n . C o n s p i c u o u s and v a r i a b l e o r n a m e nt. Max i m u m length about 3 . 5 i n .

M E SOZO I C A N D C E N OZ O I C P E L E C Y P O D S

J u ras s i c t o C reta足 c eo u s , l i ke Gryph a ea below, but with a large, massive, s p i rally twi sted l eft va lve. One va lve was attac h ed a n d the other served as a l i d . O rnaEX OGYRA,

ment is variable but u s u a l ly very stro n gly developed e i t h e r as g rowth l i nes in species to the left above or as ribs i n s pecies to t h e rig ht. Maxi足 m u m l e n g t h about 5 i n .

PIN NA, J u ra s s i c t o Recent. T h ese

P e n - s h e l l s a re tria n g u lar, large, thin and e q u i valved, with a l o n g h i nge. T h e valves a r e g a pi n g ; h i n ge teeth absent. Attac h ment to t h e bottom i s by h o rny th read s . F o s s i l s often frag m e n ta ry. M a x i m u m l e n g t h about 9 i n .

I N OCERA M U S , J u rassic t o C re足 taceo us, i s oval in o u t l i n e , with a prom i n ent beak a n d a stra i g ht h i n g e l i n e without teeth . It h as con centric, corru gated g rowth l i n es. Several species have p r o d u c e d fo s s i l pearls. Length u p to 4 ft.

G R Y P HAEA, J u rassic to Eocene,

is cal l ed Devil's t o e n a i l s . Valves a re g rossly u n equal ; l eft valve l oosely c o i l e d , r i g h t small, fiat a n d l i d - l i k e ; growth l i nes c o n s p i c u o u s . Deg ree of c o i l i ng is variable. M ax i m u m l e ng t h about 3.5 i n .

1 20

ARCA, J u ra s s i c to Rece nt, has a n

G L YCIMERIS, C retaceo u s to Re

a n g u lar outl i n e. B e a k b l u nt but c o n s p i c u o u s ; teeth a n d soc kets s m a l l . P rom i n e nt rad ial r i b s . L e n g t h 2 t o 3 in.

cent. Valves i n d i v i d u a l l y s y m m etri cal, nearly c i r c u l a r i n o u tl i n e ; p o i nted beak, with a stri ated a rea between . beak and h i n g e . Length 1 to 2 i n .

Cretaceo u s , i s a w i d e s p read c o n ical, coral- l i ke s h e l l . T h e right v a l v e i s v e r y th ick, deeply c o n i ca l a n d g rows attached to rocks. The left valve i s thick and l i d - l ike. Valves move o n thick teet h . H e i g ht about 5 i n .

HIPPURITES,

OSTREA, T r i a s s i c t o Recent. Oys ters g row atta c hed by l eft valve, w h i c h i s c o n cave, r i b bed a n d larger than rig ht valve, w h i ch is flat and often smooth. O r n a ment may in c l ud e deep folds and g rowth l i n e s ; s hape very variable. Length 2 to 6 i n .

ASTARTE, T riassic t o Recent, h a s a l most e q u a l valves, i s o v a l t o trian g ular in o utline and h a s a p ro m i n ent beak. It i s s mooth or has s c u l pt u red g rowth l i n es w h ic h fo rm c o n c e ntric ridges. Length a b o ut 0.8 i n .

121

C E N OZO I C P E L EC Y P O D S

CARDIUM, Triassic t o Recent, i s

a very c o m m o n b i valve o f nearly ci rcular o utli n e. It is e q u i valved with a con vex p rofile ; promi nent, in c u rved beak and a c u rved hinge line. Valve marg i ns wavy. Strong rad ial r i b s someti mes sc ulptu red l i ke o ver lapp i n g tiles. Length 1 to 2. i n .

UNIO,

Triassic t o Recent, is a fresh -water c l a m , oval in outli ne and equ ivalved with a b l u nt b ut promi nent beak. S u rface is smooth or h as c o ncentric g rowth l i n es. � H i nge w ith re latively few, d i v e rse, "' large teeth. Length 2 to 3 i n .

PECTEN,

�

M i ss.-Recent, is the g ro u p name for many wel l-known b ivalves. V a lves i n d i vi d ually sym metrical except for u nequal w i n g s a t end of the l o n g , stra ight h i nge, w h i c h has a triang ular l igament p it on the i n s i de. Stro n g rad i al r i b s ; s i n g l e m uscle scar. Len gth 1 to 8 i n .

ENSIS, T e rt i a ry t o Recent, i s t h e

c o m m o n , w i d e s p read raz o r shell, w ith an o l d -fas h i o ned razor outline. The m a rg i n s are a l m o st stra ight and t h e beak i s te rm i nal. O rnament is s i m p l e, of fine, con centric l i nes. Length 1 to 1 0 i n . T

1 22

RECENT

TERT I A RY

Scaphiles

CRETACEOUS J U RA S S I C TRIASSIC PERM I A N

en 0

� Belemnites � -

---

_ 6 ._ :..._ .,... z ------ <( :z:

--------:

PENNSYLVA N I A N

0 ::------ ::;: ::;: <(

M I S S I SS I P P I A N

---� �,...------ � --------! loJIIiJ' Muensterocer as

<( a:

------l

DEVO N I A N SILURIAN Diag ram s h ows t h e d evelo p m e nt of cephalopods and the d iv e rsity of 1------ each group in geolog i c time. living -----:l f o r m s a re at the t o p . CAMBRIAN ORDOV I C I A N

CE P H A LO P O D S are h i g h l y d eveloped m a r i n e m o l l u s ks ,

represented b y the l i v i n g nauti l u s , octo p u s a n d s q u i d . T h e s h e l l m a y be exte r n a l , i nternal o r a bsent, a n d it m a y be vari o u s l y c o i l e d . Living fo r m s have a w e l l -develo ped head, eyes, a n d tentacles. M o st fos s i l fo rms had wel l -develo ped s h e l l s . T h ree main g ro u ps exist. A m mo n o i d s and n a uti loids a re fou r-g i l led c e p h a l o pods with a n exter nal s h e l l d iv i d ed i nto c h a m bers by transverse p l ates o r septa. T h e a n i ma l l ives i n t h e o utermost c h a m b e r. A fl es h y sta l k perfo rates the septa. The j u n ctio n o f the septa w i t h the s he l l wa l l fo r m s the sutu re li n e. Coleo i d c e p h a l o pods (octop u s a n d s q u i d ) h ave two g i l l s a n d h ave either an internal s h e l l or n o n e at a l l . The most common foss i l fo r m s , Mesozoic c i g a r- l i ke belem n ites, a re the i nte rnal skeleto ns of s q u i d -l i ke species. 1 23

E A RLY P A L EOZO I C C E P H A LO P O DS

Cep h a l o p o ds have been traced back to t h e m id-Cam b r i a n , and i n the ea rly Paleozoic h a d a l ready become w i d e足 s p read. T h e larg est of these early forms reach ed a l e n gth of 15 feet, w it h stra i g ht or g e ntly cu rved , l o n g s h e l l s s h ow-

tran sverse secti on

side view

ENDOCERAS (Acti n oceras), Or足

GOMPHOCERAS, Ordovician to

dov i c i a n . A g r o u p of long, more or less straig ht, co n ical shells, with a la rge calc ified si p h u n cle (shown above), which has i nternal f u n n e l 足 l i ke structu res, nauti l o i d sutu res and p ro m i nent rec u rved septal necks. Max. length a b o ut 10 ft.

Devo n ia n , refers to a g r o u p of stout, b u l bo u s nauti l o i d s , with stra i g h t or s l i g htly c u rved shells and a la rge body c h a m ber. T h ey had s i m ple septa, T-shaped apertu res a n d smooth or striated s u rfaces. Length about 3 i n .

1 24

i n g s i m ple nauti l o i d s utu res (p. 36) . M o re tig htly c u rved fo rms with sharply fo lded (am m o n o id ) s utu res began to appear i n t h e S i l u ri a n . After the Devo n i a n the nauti l o i d s pers i sted , b u t they decreased i n n u m bers, w h i le late r a m m o n o i d s had wavy (stro n g l y folded) s u t u re l i nes.

DAWSONOCERAS, M i d d l e S i l u rian t o Lower Dev o n i a n , h a s a stra i g ht

c o n i cal s h e l l , with a r i n ged s u rface and wrin kled g rowth l i nes. S m a l l central s i p h u ncle. Len g t h about 5 i n .

transverse secti o n

v i ew

PHRAG MOCERAS, S i l u rian, has

DOLORTHOCERAS, Devo n i a n to

a stro n g l y c u rved, latera lly com足 pressed shell. A p e rtu re long but restri cted and with a l i p ped marg i n ( B ) and fi g u re 8-sha ped outline. S i p h u ncle on c o n cave side. Trans足 verse striat i o n s . Le n gth u s u a l l y 4 to 5 i n .

Penn sylvan i a n , has a stra i g ht, c o n 足 ical, smooth s h e l l , c i rc u lar i n cross section. The s u t u res a re transverse a n d s l i g htly s i n u o us. Has a central s i p h u n c le. Feeble c o n centric o r tran sverse o r n a m ent. Length about 4 in.

125

LATE PA LEOZO I C A N D E A R L Y M ESOZO I C C E P H A LO P O D S

lateral v i ew

ventral view

AGON IATITES has a flattened, t i g htly c o i led s h e l l with faint g rowth l i nes. The ventra l si p h u n c l e goes t h ro u g h stra i g ht septal n ecks. S u t u re very s i m ple, with ventral lobe. M i ddle Devo n i a n . D i a meter about 6 in.

BACTRITES has a straight and slender s h e l l w h i c h i s ro u n ded i n cross secti o n . Sutu res very s i m p l e, with s m a l l ventra l l o be. The s i p h u n 足 c l e is ventral. P o s s i b l y a n cestral t o a m m o n o i d s . Ordovician t o Perm i a n . Length a b o u t 1 .5 i n .

CYRTOCERAS i s a s h o rt, c u rved,

GASTRIOCERAS

c o n i cal n a uti l o i d . The shell is roun ded in c ross section and h as a p rom inent ventral s i p h u ncle. O rdo足 v i c ian to Devo n i a n . Length 2 to 3 i n .

1 26

h a s a shell which v a r i e s f r o m g l ob u lar to flat, with a prom i nent dep ression at cen足 ter of the w h orls, with a rib bed mar足 g i n . Suture with s i m p le p r i m a ry f o l d i n g . P e n n s y l v a n i a n . Diam. 1 .5 i n .

lateral view

Suture patterns adapted from Moore, Lalicker and Fischer

lateral view

B l ue d iagrams s h ow wavy s u t u re l i nes i m p o rtant in i d e ntifyi n g a m m o n o i d s ; r e d a r row p o i nts t o apert u re ( p . 73) .

M E E K O C E R A S is a fl atte ned ceph a l o p o d , g e n e r a l l y smooth, with a flat exte r i o r edge. T h e s u t u re has some seco n d a ry f o l d i n g in t h e l o bes. Lower T ri a s s i c of Idaho, Californ ia and Asia. D i a meter about 2 i n .

M U E N STEROCERAS i s a g � b � lar t o fl attened s h e l l w i t h a p r o m i nent d e p ress i o n a t the c e n t e r of t h e w h o r l s . Sutu re has deep ventral lobe, w ith stra i g ht sides. M i s s i s s i p p i a n . D i a m eter about 1 i n .

C O L U M BITES i s a flattened, t i g htly c o i l e d s h e l l with a n arched o uter edge. O r n a ment i s feeble. I t has a s u t u re w i t h m i n o r seco n d a ry fo l d i n g of the lobes. Lower Triassic. D i a m eter a b o u t 1 . 5 i n .

G O N I ATITES i s a c e p h a l o p o d with a g l o b u lar, s m ooth s h e l l s u r ro u n d i n g a s m a l l but p r o m i n ent d e p ress i o n at the center of the whorls. S utu re l i ne very d i s t i n ctive. M i s s i ss i pP.ian. D i a m eter about 1 i n .

1 27

M ESOZO I C CERATITES, M i d d l e Triassic, is a tig htly coiled, ro b u st s h e l l , with the last whorl feebly e m b ra c i n g earlier ones. The coarse r i b s do not extend to flat or b road ly arched edge of the shell. Sutu res a re distinctive. D iam足 eter about 2 in.

SAGENITES, U p per T r iassic, has a g l o bu l a r b ut c o m p ressed, tig htly coi led s h e l l . It has s p i ral a n d radial o r n a ment, the latter exte n d i n g over the shell edges. C o m plex s utu re. It may have s h o rt s p i n es. D i ameter 2 to 3 i n .

HI LDOCERAS,

Lower J u rassic, has a flattened s h e l l that i s some足 what s q u a re in cross section. It has th ree promi nent r i d g es o n the o uter edges of the w h o r l s and a wide central depres s i o n . Stro n g sickle揃 s h a ped ribbing on sides a n d com足 p lex s utu res. D ia m eter 2 to 3 i n .

HAMITES, Lower C retaceous, i s

loosely c o i l ed in o n e plane, with o n e s h o rt and two long s hafts w h ich a re c i rc u lar in c ross sect i o n . T he p ro m i nent r i b s exte nd ac ross the outer edge of the w h o r l s . C o m p lex sutu re l i n es. Length 2 to 3 i n .

CEPHALOPODS DACTYLIOCERAS, Lower J u ras

sic, a tightly coiled, flat a m m o n ite with n u merous w h o r l s . Many ribs, the l ater ones b ra n c h i n g . The ribs extend over the ro u n ded outer edges of the w h o r l s . L o n g body cham ber and c o m p l ex sutu re. D i ameter 2 to 3 in.

PACHYTEUTHIS,

J u rassic to Lower C retaceous, is a belemn ite with s h o rt, stout, b l u nt g u a rd (slen der i n y o u n g forms). Fossil is s u b o v a l , eccentric in c ross section and often large, with a g roove down o n e s i de. Le ngth 3 to 4 i n .

STEPHANOCERAS, M . J u r. , i s

thick and tig htly c o i l e d , w i t h t h e last whorl feeb l y em bracing the others ; ribs p r o m i nent, conti n u o us across the edge and b ra n c h i n g at m i d d le of w h o r l . L o n g body cham ber. A per t u re may have h o o d - l i ke l i p s . Maxi m u m diameter a b o ut S i n . , but u s u a l l y smaller.

TURRILITES, C retaceo us, has a

h i g h - s p i red s h e l l with w h o r l s barely i n co ntact. It looks l i ke a gastro p o d , b ut is d i sti n g u i s hed by p resence o f se pta and a c o m p lex pattern of s u tu res. C o n s p i c u o u s tran sverse ribs or tu berc u l e s . Len gth about 5 in.

M E SOZO I C C E P H A LO P O D S

SC A PHITES, C retaceous, i s a ftatte ned s p i ra l coil with the early whorls i n contact a n d the last one free, with s h o rt strai g ht shaft and a hoo ked e n d . Ornamented with ribs w h i c h often bran c h ; some bear tu berc u l es. Length 1 .5 to 2 i n .

B ACULITES, U p per C retaceous, has a straight shell except for a small s p i ral i n itial stage. S u rface s m ooth o r with c u rved striae or low, ro u n d ed r i bs. Suture symmetrical w i th i ntri足 cate fo l d i n g . S p e c i m e n ' s position i n total shell s h own above. Max i m u m l e n gth a b o u t 6 ft. but u s u a l l y 3 to 6 i n .

ACANTHOSCAPHITES, U p per C retaceo us, i s a t i g htly coi led s h e l l w i t h the last w h o r l g reatly expa n d e d , and often extended i nto an oval shape. P ro m i n e nt ribs and often nodes. Very c o m p l e x sutu re pattern is characte r i stic. D i ameter u s u a l l y 2 to 4 i n .

BELEMNI TES, M i ss.-Cret., are common Mesozoic cephalopods. T hey c o n s i st of long, b u l l et-like i n ternal ske l etons (guards), w ith a c o n i cal str u ct u re or d e p ression at o n e e n d . O n e s i d e of the g u ard may have a fu rrow and it may a l so have b ranched m a rk i n g s . Len gth 2 to 5 i n .

G R A PT O L I T E S are ext i n ct marine, col o n ial o rgan i s m s

related t o t h e p roto c h o rdates, a g ro u p c l o sely related t o t h e ve rteb rates. T h e typical g rapto l ite c o n s i sts o f o n e o r m o re c h iti n o u s branches (sti pes) bea r i n g c u p - l i ke stru c tu res (th ecae) . S e e p . 74. T h ey a re i m po rtant e a r l y Paleo zoic i n dex foss i l s .

•

DENDROIDS,

U p per Cambrian to M i s s i s s i p p i a n . Branch i n g fan l i ke g ra ptol ites with n u mero u s thin sti pes. May have a root- l i ke base. M a x i m u m length about 4 i n .

DIDYMOGRAPTUS,

D I PLO G R A PTUS, M i d d le Ordo v i c i a n to Lower S i l u ri a n , has a si n gle sti pe, with two rows of cl osely spaced, o b l i q u e , c u rv ed thecae. Length u s u a l l y about 2 i n .

CLIM ACOGR A P TUS, Lower O r

M O N O G R ,A P T U S , S i l u ri a n , has a s i n g l e stra i g h t or c u rved stipe, with o n e row of th ecae, which are very vari able in form. Length u s ua l ly 1 to 2 i n .

N E M A G R A PTUS, M i d d l e Ordo v i c i a n , is an i m portant a n d w i d e s p read g u i de foss i l . T h e two S s h aped sti pes g i ve rise to n u merous s h o rt branches. Length 1 .5 in.

Lower t o M i d d le Ordovi c i a n , h ave two stipes d iverg ing at a n g les u p to 1 80", and each has one row of c y l i n d rical th ecae. Length of stipe 1 to 2.5 i n .

d o v i c i a n to Lower S i l u ri a n , has a s i n g le, strai g ht stipe, with two rows of s h a r p l y c u rved th ecae. O uter walls paral lel to a x i s of stipe. Length 1 to 2 i n .

CEP H A L A S PIS is a typical m e m 足

ber of a g ro u p of c l o sely related ostraco d e r m s ( p ri m itive, jawless fi s h ) , ran g i ng from the U p per

S i l u rian through t h e Devon i a n . M o st c e p h a l a s p i d s had a fl atten e d , b o n y h e a d s h i e l d , a n d a scale-covered body. Length 6 in. to 1 ft.

VERTEBRATE FOSSILS Verteb rates (fis h , a m p h i b ia, repti les, bi rds a n d m a m m a l s) and a few m i n o r, p r i m itive g r o u p s bel o n g to t h e P h y l u m C h o rdata. A l l h ave a dorsal n erve co rd with a s u p po rt i n g rod ( n otoc h o rd ) late r replaced b y t h e verteb ra l co l u m n i n verte b rates. A l l have g i l l s l its i f o n l y a t s o m e stag e of their life histo ry . Fis hes, the o l d est verte b rates, are div i d ed into fo u r classes : a g n atha, the jaw l e s s fis h ; p l a c o d e r m s , the p l ate足 ski n n ed fish ; ch o n d richt hyes , the sha rks a n d ray s ; a n d osteichthyes, the bony fis hes. The a g n ath a, the most pri m itive verte b rates, l ack pai red fins and true jaws . The o l d est fossil verteb rates a re O r d o足 vician b o n y fra g ments from Wyoming a n d C o l o rado. M ost fossil ag n atha were ostraco d e r m s , w hich were covered by an a r m o r of bony p l ates o r sca les. They i n足 c l u ded both m a rine a n d fresh-water s peci es . Both a re wid esp read in Devonian st rata. No a g n atha a re known in p o st- Devo nian rocks. Thei r l i vi ng re p resentatives (the pa rasitic l a m p rey and hag fish) s u g g est the l ater fo rms may have been soft-bod i e d . 1 32

PTER A S P I S, an U p p er S i l u r i a n t o D e v o n i a n ostra c o d e r m , is a s m a l l strea m l i ned fi s h . T h e h ead i s e n 足 c l o sed i n t w o large oval p l ates, w i t h a rear spine and gill openings. Length a b o u t 6 i n .

A N G L A S P I S i s a D e v o n i a n ost ra足 c o d e r m , has a l a r g e oval h ead s h i e l d , and w i d ely s paced eyes. T h e t r u n k a n d ta i l a r e cove red by d i st i n ctive scales. Length a b o ut 6 i n .

M i d d l e S i l u r ian to Lower Devo n i a n . The e n t i re body of t h i s ostrac o d e r m i s covered with stu d - l i ke, i nterloc k i n g d e n t i c l e s . S m a l l lateral eyes ; m o uth below ; flatte ned b o d y . L e n g t h 3 to 8 i n .

Lower Devo足 nian, has a very l a r g e , fl attened h ead s h i e l d of large and s m a l l f u s e d p l ates. V e rteb rate f o s s i l s a re u s u a l l y i n c o m p l ete u n l i ke w h o l e s p ec i m e n s s h o w n h e r e . L e n g t h 1 ft.

THELODUS,

DRE P A N A S P I S ,

P LA CO D E R M S (plate-ski n n ed) a re an ext i n ct ( U p per

S i l u rian to Perm ian) c lass of fishes w ith p r i m itive jaws and pai red fi n s . A variety of fo rms i n c l u d es acant h o d i a n s ( s p i n y s h a rks) , s m a l l , s p i ny-fi n ned, stream l i n e d , fresh water fi s h , w h i c h were cove red b y t h i c k s cales ; art h rod i res (jo i nted - n ecks) , with a h eav i ly armored h ead and s h o u lder reg i o n , and wide gap i n g jaws ; and antiarc h s , smal l , ar m o red , b o x- l i ke bottom dwell ers, with powerf u l , arm l i ke fi ns , a b u n dant in the m i d-Devo n i a n .

PTERICHTHYS, D evonian . Front part of body covered with h i g h ly arched, fused plates ; rear with scales. C l osely spaced eyes. Stro ng "arms." Length 6 in.

COCCOSTEUS, D evo n ian, a j o i nt

BOTHRIOLEPIS, Devo n i a n , an antiarch with front h eavily armored by a s h o rt head s h i e l d and a l o n g , box- l i ke b o d y s h i e l d . L o n g , joi nted "arms." Le ngth about 9 i n .

CLIMATIUS, Upper S i l u rian t o De

ed neck art h ro d i re with armored head and thorax. Rest of body naked. Exposed bony plates se rve as teeth. Length 18 i n .

v o n i a n . A s p i n y acanth o d i a n " s h a rk" covered with r h o m b o i d scales, 2 s p i nes on back ; 5 p a i rs of ventral fins. Length 3 i n .

S H A R KS A N D RAYS ( C h o n d ric hthyes) h ave a skele ton of carti lage a n d o pen g i l l sl its. M o st a re marine p reda tors with w e l l -d evelo ped teeth and are p rotected by b o n y sca l e s . T h ese a n d a n occa s i o n a l s p i n e a re u s u a l l y t h e o n l y foss i l s fo u n d . I n contrast t o placoderms, s h a rks have two pa i rs of pai red fi n s, and m o re special i z ed jaws a n d teet h . T h e o l d est s h a rks ( D evo n i an) u n d e rwent g reat ex pa n s i o n in the U p per Paleozo i c . Mesozoic and C e n oz o i c fo rms were w i d e s p read .

PLEURACANT HUS,

n i a n . Wel l-d eve loped, b road fi n s and strea m l i ned, w i t h naked body. Teeth n u merous, poi nted. M ax i m u m l e n g t h a b o u t 4 ft.

Pen n .Perm., is a fresh-water shark, with g reatly elongated dorsal fi n and pointed tai l . Paired, leaf-shaped ven t ral fins. Spine at back of h ead. Length u s u a l ly a b o ut 2.5 ft.

SHARK T E ETH are c o m m o n fos s i l s i n some rocks of the M iocene. Larg est are those of Carcharodon, a 40- to 50-ft. s h ark. M o st fossil teeth a re well-preserve d .

R A Y S A N D S K AT E S , J u rassic to Recent, are b otto m dwel lers , with flatte ned bodies, huge pectoral fi n s and h eavy, s hell-c r u s h i n g teeth . Rare as foss i l s .

CLADOSELACHE, U p per Devo

From a photo b y Smithsonian I n stitution

135

B O N Y F I S H ES (Osteichth yes) a re t h e m o st a b u n dant,

d i verse and co m p lex g ro u p of fis hes. T h ey o u t n u m ber all oth e r fis hes twenty to o n e a n d i ncl ude m o re s pecies than a l l other verteb rates com b i n e d . Bony fi s h es have a bony skeleton a n d s l i my, sca l e-covered bodies. S o m e fos s i l a n d a few l i v i n g b o n y fi s h es have l u n g s ; t h e rest have a n a i r b l adder that contro l s b u oyancy. Most of the early bony fishes had . strea m l i n ed bodies and wel l-develo ped fi n s . These featu res perm itted active sw i m m i n g w ith m i n i m u m d i stu rba nce of the water a n d co ntrib uted t o the fi shes' ra p i d expa n s i o n . Large eyes and m o u t h s , a i d s in eva s i o n and food gath eri n g , also hel ped b o n y fi shes to fl o u r i s h i n lakes, strea m s a n d seas. S pecific adaptat i o n s to u n i q u e e n v i r o n ments deve l o ped . The o l d est (Mi d d l e Devo n i a n ) b o n y fis h es had th ick enamel sca l es, w h ich became l i g hter in later fo rms. I n the ray-fi n n ed (act i n o pteryg i a n ) forms the fi n s a re s u p 足 ported by m a ny s l e n d e r ray- l i ke b o n e s . Paleozoic ray足 fi n n ed forms were a s m a l l fresh-water g ro u p , w h ich late r g rew a b u n d a nt i n the seas. O n l y a few s u rv i v i n g fis h , such as stu rgeo n , represent these p r i m itive ray fi n s . Early fo rms were re p l aced i n Mesozoic ti mes by h o l eo st ray fins, with more co m p l ex and efficient skeleto n s , jaws a n d scales. S u rv i v i n g h o l eo sts i nc l u d e the garp i ke a n d b owfis h . I n C retaceo u s ti mes m o st of the h o l eosts were rep l aced by the m o re advanced tel eost ray fins, w h ich i ncl u d e a l m ost all l i v i n g fis h . The other m a i n g ro u p i s the l o be fins ( C h oa n ichthyes) . I n t h i s g ro u p , the fi n s a re s u p p o rted by a stro n g b o n y axis a n d the n o stri l s o pen i nto the m o u t h . Lobe fins i n 足 c l u d e l u n g fi sh ( D i p n o i -Devo n ian to Rece nt) a n d t h e fri n g e fi n s (cro sso pteryg i a n s ) . I n t u r n , the fri n g e fi n s i nc l u d e coelacanths a n d the smal l , powerfu l , ca r n i v o ro u s fis hes o f t h e Devo n i a n from w h ich t h e a m p h i b ia arose. 1 36

B O N Y F I S H ES RAY FIN, s h ow i ng ty pical struc

LOBE FIN, showing ty pical struc

t u re of s u p p o rt i n g bon es, c h a rac teristic of m ost l i v i ng fi s h .

t u re of stro n g , s u p po rt i n g b o nes from w h i c h feet develo ped (p. 1 38) .

CHEIROLEPIS is a M i d d l e

De vonian ray-fi n n ed fish. It is probably similar to the forms that were an cestral to a l l later bony fishes. Length about 11 i n .

OSTEOLEPIS, M i d d le Devo n i a n ,

LEPIDOTUS, a J u rassic h o l o stea.n

HOLOPTYCHIUS

ray fi n , is a deep-bodied species with d o rsal fi n set far back and with 'tw o pai red fi n s and anal fin below. It had strong c r u s h i n g teeth and heavy en ameled scales. Length 12 i n .

a p r i m itive f r i n g e fi n (p. 1 38), with th ick, rh o m b i c scales ; w e l l - s paced median fi n s , s h o rt, lobed, pai red fi n s and s i m ple teeth. Len gth 9 i n . is an U p per Devo n i a n s peciali zed fri nge fi n (p. 1 38) , with t h e median fi n set well back on the body a n d with l o n g , l o bed, paired fi n s below. Scales are r o u n d ed. Length about 2.5 ft.

DIPTERUS, Devonian, is a primi tive l u n g fi s h with stream l i ned body, . strong pai red fi n s , h eavy c r u s h i n g teeth, scales and a rather red u ced bony skeleton. Len gth 15 i n .

L O B E F I N S , C h o a n ichthyes, (l u n g fish a n d fri n g e fins) are a i r- b reath i n g b o n y fi sh (Devo n i a n to Recent) w ith i n te rnal n o stri l s a n d stro n g l y s u p p o rted fi n s . T h ree g e n e ra of l u n g fish ( D i p n o i ) s u rv ive. The fri n ge fi n s (crosso pte ryg i a n s ) , a ncestors of a m p h i b i a , i ncl u d e l i v i n g coela ca nths and a b u n dant Devo n i an fo rms.

EUSTHENOPTERON,

from the Dev o n i a n , i s a powerful carnivorous fringe fi n or crossopteryg ian. It has a n adva nced stru ctu re and charac teristics and is closely related to the an cestors of the a m ph i b ia. Length 2 ft.

COELACANTHUS,

M iss.-Perm., i s a ty pical deep-bod ied, lobate fi n ned coelacanth, such as were common in the Mesozoic. T h o u g ht to be exti nct, the fi rst l ive coelacanth was caught off M a dagascar in 1 938. Length u s u a l l y less than 1 .5 ft.

p r i m itive a m p h i b i a n , w ith many fi sh足 l i ke cha racters ( b ones of s k u l l , ver足 tebrae, tai l ) , but others al ready a m p h i bian ( stro n g s h o u lder and h i p g i rd l es, l i m bs, r i b s ) . Len gth 3 ft.

A M P H I B I A are the s i m p l est tetra p o d s , the fi rst class of verteb rates to i n vade the l a n d . T h ey are o n l y partly ada pted to land l ife, as n early a l l lay eggs in water a n d l a rvae a re g i l l - b reath i n g , aq uatic c reatu res that o n l y later develop l u n g s and fo u r l i m bs . M o st living fo rms (fro g s , toad s, salamanders) l i ve i n d a m p e n v i ro n ments. T h e o ld est am p h i b ia ( i c hthyosteg i d s) come from the U p per Devo n i a n of G ree n l a n d a n d reta i n m a n y c h a ra cters rem i n i scent of t h e i r crossopteryg ian an cestors (p. 1 37) . M o st ea rly a m p h i b i a were labyri nth o d o nts with i nfo l d ed enamel i n t h e i r teeth . T h ese were s p raw l i n g carn i v o res, u p to 1 5 ft. l o n g . M i ss i ss i p p i a n to Triassic. ERYOPS,

Permian, is a large carn i vorous labyri nth odont; h eavy足 bod i ed and squat with a large tri足 a n g u lar sku l l ; s h o rt powerful l i mbs. Well adapted to l a n d l ife. Length 5 ft.

1 39

"BRANCHIOSAURUS," Perm i足

EOGYRINUS, P en n sylvanian . The deep powerful body a n d weak l i m b s of th i s very l a rg e s alamander s h o w i t w a s largely a q u atic in its habits. Length 1 5 ft .

an, a re larval labyrinthodo nts, with external g i l l s and less bony skeleton than ad ults. Properly known by generic n a m es . Length 2 to 3 i n .

DIPLOCAULUS,

CACOPS, Permian, i s a s m a l l land

Permian, is a wedg e-hea d ed salamander with weak legs. The s paci n g of the eyes and body s h a pe s u g g est a l ife that was l a rgely aq uati c. Len gth 2 ft .

labyrinthodont with well-d eveloped legs, armor p lates on back, s h o rt tail and h eavy skull. Length to 16 i n .

Penn., a small pri mitive a m p h i b ian with a l o n g body but l i mbs very weak in comparison with l ater forms. Skull q u ite s i m i lar to c rosso pterygian fish. Length 3 ft .

R E P T I LES ( P e n n sy l van ian to Recent) a re c o l d - b l ooded , egg-lay i n g verteb rates i n c l u d i n g crocod i les, t u rtles. l i zards and s nakes. Fos s i l fo r m s , m o re n u merous and w i d e s p read , d o m i nated Mesoz o i c l ife. Reptiles a re bette r adapted to land l ife than a m p h i b ia n s . Fert i l i zati o n i s i nterna l ; e g g s are l a i d o n l a n d a n d i n c l u d e a foo d s u p p ly a n d a p rotective coveri n g . Repti les a re p ro tected by a s k i n w i t h s c a l e s o r plates. T h ey b reathe a i r through lungs. Some o f t h e ea r l i est repti les (sey m o u ria m o rp h s ) s h owed · a m i xtu re of a m p h i b i a n a n d repti l ian c h a racte rs. Oth e r early repti les i nc l uded pareiasau rs, pelycosa u rs, mam ma l - l i ke th e ra s p i d s , a n d aq uatic mesosau rs. T h e r u l i n g Mesozo i c repti l es i n c l uded d i n o sau rs o n t h e l a n d , pte ro sau rs in the a i r and six g ro u ps in the seas. Repti les d e c l i ned g reatly at the c l o se of the Mesozoic E ra. O n l y fou r of fifteen major rept i le g ro u p s sti l l s u rvive. A l l g ro u ps , exti n ct and s u rvivi n g , have c h a racteristic sku l l structu res. EDAPHOSAURUS

a small s k u l l ed vegetarian pelycosa u r devel oped a vertebral "sail" l i ke Dimetro don, a larger-s k u l l ed carni vore. Com pare t h em o n p. 1 42. Permian.

SEYMOURIA, Permian, i s a very

p r i m itive repti le, w ith many a m p h i b ian c h a racteristics but w ith d i sti n c tive repti l i a n verteb rae a n d well d eveloped l i m bs. Length 2 ft.

c a r n i v o ro u s pelyco sa u r. Length about 8 ft. OPHIACODON, Permian, a

fi s h-eat i n g rept i l e . 揃 length about 8 ft.

Maximum

E V O L U T I O N OF T H E M A M M A L- L I K E R E P T I L E S After E. H . C o l b e rt

E A R L V M E SOZO I C R E P T I LES i n c l ude a g reat variety of forms, m o st of w h i c h arose in the Perm ian from a n a n cesto r n ot g reatly d ifferent fro m Seymouria. Mesozo i c forms i n c l u d e sea-g o i n g t u rtles, p l acodo nts a n d i c hthyo足 saurs as well as many terrestrial fo rms. A m o n g the land repti les were sa i l - bac ked pelycosa u rs , m a m m a l - l i ke rep足 t i l es a n d s m a l l b i pedal thecodonts, w h i c h were the an足 cesto rs of d i n os a u rs , b i rd s , croco d i l es , s na kes a n d fl y i n g pte rosau rs. T he repti l i a n con q u est o f l a n d , s e a a n d a i r i s o n e o f the m aj o r events o f earth h i sto ry. N o other g ro u p of a n i m a l s except t h e m a m m a l s have s h ow n s u c h a ran g e of adaptat i o n s t o va ried c l i mates a n d e n v i ro n m ents . 1 42

sea serpents, probably evolved from l i z ard - l i ke a n cesto rs. Pow erful, crocod i l e- l i ke bod ies, stro n g jaws a n d teet h , and well developed paddles. Le ngth 30 ft.

AMPHICHELYDIAN t u rtles, ancesto rs of present land and sea forms, a rose i n the Trias s ic. Some C retaceous t u rtles reached 1 2 ft.

PLES IOSAURS, J u rassic to C reta·

ICHTHYOSAURS, or fish lizards, are carn ivorous ma ri n e repti les (Tri assic to C retaceo us) , with stream l i ned fish - l ike b od i es. W e l l - pre served foss i ls show they g ave b i rth to live you n g . Len gth u p to 30 ft.

ceous, were marine c a rn i vores. T h ey were active s w i m mers p ro p e l l ed by powerfu l padd les. Some were long' necked, with s m a l l heads and long ta i l s ; ot hers were s h o rt-necked and lon g -h eaded . Le n gth 15 to 40 ft.

NOTHOSAURS PLACODONTS a re Triassic,

mo l l u s k-eati n g repti les, with wa l ru s - l i ke bod ies and h i g h ly special ized teet h . So me forms had b o ny armor on the back. Length about 11 ft.

are s l i m , fi s h-eat i � g a m p h i b i o u s rept i l es from the Triassic, related and perhaps a n cestral to the p l esio sau rs. Length 4 ft.

After E . H . C o l bert

M ESOZO I C M A R I N E R E PT I LES d o m i n ated the ocea n s as d i n os a u rs did the l a n d . Using pad d les a n d l u n g s i n stead of fi ns a n d g i l l s , th ese descen da nts of fo rmer l a n d a n i m a l s became h i g h ly ad apted to sea l ife. T u rtles and m o sasa u rs develo ped from d iffe rent an cestral sto ck than oth e r m a r i n e rept i l e s . 143

D I N O S A U R S , the terri b l e l i zards, a re the best known of a l l repti les. T h ey d o m i n ated l ife o n the land d u ri n g m ost o f t h e Mesoz o i c Era, a period o f a b o ut 1 40 m i l l i o n yea rs. D i n os a u rs a rose from a g ro u p o f T riassic theco dont repti l e s and are rep resented by two main ty pes. One g ro u p , the sa u risc h i a n s , had a rept i l ia n h i p stru ctu re. The oth e r g ro u p , the o rn it h i s c h i a n s , were b i rd - h i pped d i n o sa u rs. Sau r i sc h ia n s deve l o ped i nto two d i st i n ct g ro u ps of d i n osau rs. The m ost p r i m itive were the theropods, the o l d est of w h i ch were small (5 ft. ) , s l e n d e r, b i pedal c rea tu res, w ith a l o n g bala n c i n g tail. Later forms i n c l uded the g iant carn i v o res. T h e seco n d g ro u p were the sauropods, m o st of w h i c h were large, fou r-footed , l o n g - n ecked h e rbi vores . The l a rg est of th ese g rew u p to 87 ft. l o n g . Teet h , s h a rp i n carn ivores a n d b l u n t i n herbivo res, u s ua l l y ex te n d ed the l ength of both jaws. O rn it h i s c h i an d i n osau rs i n c l uded fo u r g ro u ps . Steg o sau rs were 20-ft. h e r b i vo res w ith a h i g h -a rc h e d , armo red back from w h ic h h eavy bony plates rose in a d o u b l e row, and a s p i ked ta i l . O rn ithopods we re s e m i-aq u atic, d u c k b i l l e d , b i p edal d i n osa u rs w ith we b b ed feet. T h e larg est were about 25 ft. l o n g . Some o rn ith o p o d s had c rested a i r sto rage st r u ctu res o n the sku l l . A n ky l o sa u rs were armo red , ta n k- l i ke d i n osau rs ; with stro n g ly c u rved r i b s , w h o se b road backs were cove red by overla p p i n g bony p l ates, some m o d ified i nto s p i kes . T h ey were 20 ft. l o n g . Cerato p s i a ns were h o rned d i n o sa u rs ran g i n g from 5 to 20 ft. i n length, with t h i ck h ead a n d neck a r m o r. They were wel l - p rotected p l a nt-eate rs . D i n o sau rs were worldwide i n d istri bution a n d i n ha b ited a variety of d ifferent env i ro n m ents. T h e reason fo r t h e i r exti ncti o n a t t h e c l o se o f C retaceo u s ti mes i s not known . 1 44

S I M P L I FI E D FAM I LY T R E E O F T H E D I NOSA U RS

SAURISCHIANS

JURASSIC TRIASSIC THECODONTS A n cestors of the d i nosaurs After E. H. C o l bert

1 45

ARCHAEOPTERYX,

J u rassic, a prim itive c row-si zed b i rd with many rept i l ia n featu res. K n own from the Solen h ofen l i mestone q u a rries in Germany. 18 i n .

B I R D S a re w i n g e d , feat h e red, wa r m - b l o o d e d , e g g - l ay i n g verteb rates . T h e o l d est k n o w n b i rd , Arch a eopteryx, s h ows many repti l i a n c h a racte r i stics ( s u c h as teet h , c l awed w i n g s and a repti l i an ta i l ) . B i rd s probably arose from thecodont (socket-toothed) rept i l e s , from w h i c h d i no足 saurs, crocod i l es a n d pterosau rs a l so evo lved. Their deli足 cate skeleto n s a n d way of l ife make b i rds u n co m m o n as fos s i l s . C retaceo u s fo rms i n c l ude sea b i rd s and d i vers. The Cenozoic i n c l u des a n u m b e r of g i a nt, fl ig htless, car足 n iv o ro u s b i rd s , s o m e 1 0 ft. h i g h . HESPERORNIS,

a C retaceous toothed, loon-l i ke, fl i g htless sea b i rd , well adapted for s w i m m i n g a n d div足 ing. N ote the smal l , a l m o st u seless w i n g s . Max i m u m l e n gth about 6 ft.

PHORORHACOS, a h eavy- b i l led, fl i g ht less M iocene l a n d b i rd from South A m e rica. Hei g ht about 5 ft .

M A M M A L S (J u rassic to Re ce nt) a re warm - b l ooded verte b rates that s u ckle t h e i r yo u n g . Most m a m m a l s have h a i r o r fur, stro n g l y d ifferentiated teeth a n d h i g h ly d eveloped s e n s e s . T h ey are the d o m i nant g ro u p of l iv i n g MEGATHERIUM, a P l eis a n i ma l s t h e world over. tocene g r o u n d s l oth . Length M o n otremes a re p r i m itive, egg 20 ft. lay i n g mammals that i n c l u d e the d u ck- b i l led p laty p u s and s p i ny anteate r. No m o n otreme fos s i l s a re k n ow n befo re the Pleistoce n e , b ut t h ey p rob a b l y develo ped m u c h earl ier. M a rs u p i a l mammals (ka n g a roos, oposs u m s) have yo u n g w h i ch a re i m m at u re at b i rth a n d a re s h elte red i n the mother's p o u c h . M a rs u p ia l s (U pper C retaceo u s to Re cent) w e re c o m m o n in South A me r i ca. G eo g ra p h i c i s o l a tion a i d ed t h e d ev e l o p m e nt of th i s u n i q u e fa u n a there a n d a l s o i n A u stra l i a w h ere t h e y sti l l pers i st. P lacental mammals (C retaceo us to Recent), the largest g ro u p , have an i nte rmed iate structu re (th e p l acenta) by w h i c h the e m b ryo is n o u ri sh ed . C a r n i vo res ( d o g s , cats, sea l s ) a re fl e s h -eat i n g p lacental m a m m a l s . Fo s s i l fo rms i n c l u d e creo d o nts, fi s s i pe d s and p i n n i ped s . C reodo nts, archaic T e rtiary ca rn ivo res, were m o stly rath e r s m a l l , s l e n d e r a n d l o n g -ta i l ed . F i s s i peds, s p l it-footed carn ivores, re p l aced the creodonts. T h ey probably arose from weasel l i ke a n cesto rs. M o d ern fi s s i p eds ( d o g s , bears, weas e l s a n d cats) evol ved a t vari o u s ti mes d u ri n g the Tert i a ry . M o st h a v e g o o d fo s s i l records. P i n n i pe d s , web-footed carn ivores, i n c l u d e s ea l s and wa l r u ses, w h i c h p ro b a b l y evolved from d o g - l i ke a n cestors i n M i ocene t i m e s . M a m mals ra n g e i n s i z e f r o m 2-i n . sh rews t o b l u e w h a les, over 1 00 ft. l o n g , the la rgest known an i m a l s . 1 47

O X YAENA, Paleocene to Eocene,

i s a ca r n i vorous creodont. Com pare its str uct u re with Phenacodus, below. Length 3 ft.

H O O F E D M A M M A LS ( u n g u lates) a re ma i n ly rather large h e r b i v o res. They i ncl u d e l i v i n g ho rses, catt l e , e l e p h a nts a n d h i p p o s , as w e l l as sea cows a n d a few fo s s i l fo rms w i t h claws rather t h a n h oofs. The o l dest u n g u lates fro m the Pal eoce ne i nc l u d e s m a l l co n d y l a rt h s , with o n l y part l y m o d ified teeth a n d either claws o r very r u d i m e ntary h oofs, a m b l y po d s , up to 4 ft. h i g h , with elephanti ne l i m b s , and the larger u i ntatheres. I n Eoce ne t i m es t h ese forms were re p laced by o d d -toed , exti nct tita n otheres a n d cha l i cotheres as wel l as by p r i m itive r h i n o s , h o rses a n d ta p i rs. · Eve n-toed u n g u lates (deer, ca m e l s , p i g s , catt le) ap pea red in the Eoce n e , a n d in late Tert iary times largely d i s p laced the o nce a b u n dant odd-toed u n g u lates. T h e h o rse a n d rh i n oce ros a re the best known l iv i n g o d d -toed u n g u lates. The evo l u t i o n a ry h i story of many ho ofed m a m m a l s is known in co n s i d erable deta i l (pp. 5 and 67} ; some a re class ics i n paleonto l ogy. UINTATHERIUM, Eocene, i s the typical s i x- horned, h e rb i vo rous u i n that h e re, of interest because o f its h i g h l y mod ified teeth. Length 1 2 ft.

1 48

PHENACODU S, P a l eocene to Eo

cene. A n advanced c o n d y l a rth, but still reta i n i n g a long tai l , five d i s c rete toes and a carn i v o re- l i ke s k u l l . L e n g t h 6 ft.

MOROPUS, a M i ocene, h o rse s ized c h a l i cothere, with titanoth ere l i ke teeth. Its t h ree f u n ctio nal-toes a re developed i n to stro n g c l aws. Height a b o ut 6 ft.

BRO NTOTHERIU M , O l i g o c e n e . 8 f t . h i g h . The l a rgest of the titano t h eres. Early titanotheres were slen d e r, hornless c reatures, o n ly about 2 ft. h i g h .

E D E N T A T E S a re a g ro u p of m a m m a l s with m uch re d uced teet h . They o r i g i nated in So uth A m er ica a n d late r m i g rated i nto N o rth A m e rica. Two m a i n g ro u p s have d evel o p e d . One, the a rmad i l los, is p rotected by h eavy a r m o r over the s h o u l d ers a n d h i ps , j o i n ed by fl ex i b l e p lates. The o l d est fo rms come fro m the Eocene, and rel ated l ate C e n o z o ic forms i nc l u d ed t h e g i ant g l ypto d o n ts w ith m as sive sol i d a rm o r. The other g ro u p of edentates i n cl u d e s t h e t ree s l oths, anteaters and the ext i n ct g ro u n d s l o t h � . Some of the g reat P l ei stoce n e g ro u n d s l oth s were u p to 20 ft. l o n g . They fed o n l eaves a n d f r u i t b rowsed from trees. N O T H ROTHERIU M , P l e i sto cene. A s m a l l ground s l oth, about 7 to 8 ft. l o n g , was a contem p orary of early man i n the sout hwestern U n ited State s .

known from the P l e i stocene, is a special ized e d e n tate with fu sed b o n y a r m o r a n d a heavy a rm o red ta i l , some e n d i n g i n a s p i ked c l u b . L e n gth 9 ft. GL Y P TO DON,

1 49

CRYPTOZO O N "REE F", Cambrian. T h ese and s i m i la r l y

sha ped l i m esto ne featu res w e r e p roba b l y m a d e by s i m p l e algae.

FOSSIL PLANTS P l a nt l ife has always been the bas i s fo r a n i ma l l ife but p lant foss i l s a re less n u m e ro u s and p lant l ife of the past is less wel l k n o w n . Note the m a r i n e and land p l ants in the d i o ramas fro m p. 34 to p. 69 . T H A L LO P H YTES

T h a l l u s p l a nts a re s i m p l e , lac k i n g roots, ste m s , l eaves and c o n d u cti n g cel l s . A l gae, thal l o p h ytes with c h l o ro足 p h y l l , m a n ufact u re t h e i r own foo d . Of seven large g ro u p s , o n l y a few are p reserved as foss i l s . S o m e g o back t o P re足 Ca m b rian t i m e . T h a l l u s p l a nts with o ut c h l o ro p h y l l i n c l u d e fu n g i , s l i m e m o l d s a n d bacte ria. T h ese have l eft even less of a foss i l reco rd . CHAR N IA ( left), U pper P re-Cambrian, i s a d i s p uted

fo s s i l known from E n g land and A u stralia. It i s rega rded by some as an alga and by others as a sea pen - one of the coelente rates. Length 4 to 8 i n .

DIATOMS, C retaceous t o Recent, are small u n i ce l l u l a r

a l gae, u s u a l ly m i c roscopic. They a re free float i n g a n d h a v e deli cate s i l iceous skeleto n s . D iatoms occur in both fresh and salt water. T h ese m i n ute a l gae form deposits of d iatomaceo u s earth as m u c h a s 3,000 feet th ick. A bout 1 0,000 living s pecies a re know n . Some of them seem i d e ntical w ith those of the C retaceo u s .

ASTEROXYLON, a Devo n ian psi足

l o p s i d , h as a s i m p le b ra n c h ed stem, with l eaf- l i ke a p pe n dages. M o re complex than Rhynia. Length to 1 0 i n .

RHYNIA,

a Devon ian p s i l o psid, has a naked, b ranched stem beari n g term i n a l s p o re cases. O n e ofthe s i m足 p l est vasc u l a r p lants. Length to 8 i n .

E M B R Y O P H YTES

In this large a n d i m po rtant g ro u p of p l a nts the fert i l ized egg deve l o p s i nto a n e m b ryo which i s e n c losed i n some form of p rotective sac o r coveri n g . Fi rst i n this g ro u p are the b ryo p h ytes, w h i c h i n c l ude m os ses a n d l i verwo rts. These a re the o n l y e m b ry o p h ytes with o ut s p e c i a l i zed vasc u la r t i s s u es (see below). T h ese s i m p l e land p la nts of m o i st p laces a re rare as fo s s i l s . P e n n sylva n i a n to Recent. V A S C U L A R P L A N TS

These p l a nts c o nta i n s p ecial i zed c o n d u cti n g t i s s u es (xy lem a n d p h l oem ) u s u a l l y with true ro ots, ste m s a n d leaves . Fos s i l s q u ite c o m m o n a n d w i d e l y d i stri b uted . P S I L O P S I D S , the s i m p l est vasc u la r p l a nts, have s m a l l sca l e- l i ke l eaves o r n o n e at a l l . Roots a re lacki n g . C o m 足 m o n i n the Devo n i a n , they i n c l u de the o l d est know n l a n d p l a nts fro m the S i l u rian o f A u stra l ia. O n l y fo u r s pecies s u rvive. Two foss i l s a re s h own above. S P H E N O P S I DS , o r arth rophytes, i n c l u de l i v i n g h o rse足 ta ils and scou ri n g r u s h es . T h ese p l ants with r i b bed , j o i nted ste m s and c i rc lets of l eaves bear s p o res i n c o n es at t i p s or on sta l ks. Pen nsylvan ian forms (Calamites) g rew 40 ft. h i g h . Devo n ian to Recent. 151

CALAMITES,

M is s i s s i p p i a n to 路 Perm ian. A s c o u r i ng rush ( s phe颅 nopsid) with r i b b ed , joi nted t r u n k, a n d l eaf w h o rls at jo i n ts . Ht. to 40 ft.

SPHENO PHYLLUM, Devo n i a n to T r ia s s ic. S m a l l with slender r i b b ed stems a n d circl ets of fan-sha路 ped leave s , 0.3 i n . l o n g p i n n u les.

L Y C O P O D S , Devo n ian to Recent, a re vasc u lar p lants w ith s i m p l e l eaves i n s p i ra l s , n ever i n c i rclets. Stem i s n ot j o i nte d . T h i s g ro u p , w h i c h i n c l u d es l iv i n g c l u b m o sses, reac h ed its z e n ith as large trees i n the late Pa l eo z o ic. S o m e lyco pods h a v e two d i sti n ct types o f s p o res. Foss i l s are c o m m o n , e s pec ia l ly associated with coal-bea r i n g strata.

Pen nsylva n ia n . SIGILLARIA, Stout t r u n k, w i t h b laded leaves a n d vertical l eaf scars. M a x i m u m h e i g ht a bout 1 00 ft .

LEPIDODENDRON,

Pennsy lva颅 n i a n . Tall, b ra n c h i n g , w ith slender l eaves and d i a m o n d leaf scars. Max i m u m h e i g ht abo ut 1 00 ft.

STIGMARIA, P e n n sylvanian ; the roots of lycopod trees. Su rface pitted with i rreg ular s p i ra l s of rootlet scars. L o n g est are 40 ft. in length.

root system

1 52

ro otlet projections

F E R N S a re an o l d g ro u p of vasc u l ar plants often with

large, c o m p lex leaves that may bear s p o re cases o n the u n d ers i d e s . T h ey became common i n the Pen n sylva n ia n a n d a re sti l l co m mo n today. M a n y fern- l i ke fos s i l s a re n ot true ferns, b u t seed fe rns (below). G Y M N OS P E R M S , the s i m p lest seed p l ants, p ro s p e red because the male p o l l e n g ra i n s res ist d ry i n g , w h i l e i n s i m pler e m b ryo p h ytes the male cel l m u st be m o i st. Gym n o s perms h ave n o fl owers and seeds a re not fu l ly en c l o sed. Li v i n g and exti n ct g y m n o s pe r m s fal l i nto five g ro u p s, i l l u st rated o n p p . 1 53-1 54. The seed fe rns are a n ext i n ct g ro u p wh ich deve l o ped s e e d s o n th e i r leaves, n ever i n c o n es ( Devo n i an-J u rassic). T h e Mesm;oic cy cad eoids and the closely rel ated cycads h ad a ring of narrow pa l m - l i ke f ro n d s g row i n g from a ro u n d ed t r u n k. T h e . cycad s d iffer from the cycadeo i d s i n havi n g the m a l e a n d female c e l l s i n sepa rate cone-l i ke st r u ct u res (Perm ian-Recent) . The co rdaites were ta l l trees with s l en d er, strap- l i ke l eaves (Pen nsylvan ian-Trias s i c ) . G i n kg o s (Triassi c-Recent) , c o m m o n i n the M es o z o i c , i n c l u d e o n e l i v i n g species. C o n ifers, m a i n l y need l e-leaved , with c o n es, a re n ow m o st c o m m o n . ( P e n n sylvanian-Recent.) NEUROPTERIS, M i ss. - Perm., frond of a seed fern with c u rved vein l ets ; oval leaflets a lte rnate on either side of ste m . Length of pinn u les 0.25 0.5 i n .

ALETHOPTERIS, Penn., another

seed fern with long, blade- l i ke l eaf lets, wider at the base. M i d - r i b vein is very d i sti n ct. Length of p i n n u l es 0.5 i n .

1 53

G Y M N OS P ERMS

actual foss i l ( Be n n ettita les) , CYC ADEOIDS T riassic to C retaceous, d o m i nant i n M esozoic, rese m b l e l i v i n g cycads b u t rep rod uction d i sti n ct. H e i g ht 2 to 1 2 ft .

SPHE N O P TERIS,

D e v o n i a n to P en n sy l van i a n . F rond of a seed fern ; small, s y m m etri cal, lobed l eaf l ets with ra d iati n g veins. Length of p i n n u les 0.4 i n .

leaf

to Trias s i c , g rew worldwide in Late Pa leo z o i c . Possi b l y anc estral to con ifers. Maxi m u m h e i g ht a bo ut 1 00 ft. LEB ACHIA, a

Pen nsylvanian to Permian c o n ifer, had a stra i g ht t r u n k and s p i rally arran g ed needle l i ke leaves. Bra n c h shown about 1 0 in. long.

WIL L I A M S O N I A , Triassic t o C re taceo us. Cycadeo i d plants with b u l bous stem covered w i t h s u n ken leaf bases. "Fl owers" on long stems. Height about 6 ft. GIN KGO,

Triassic to Recent-a l i v i n g foss i l , with leaves on s h o rt s p u rs. Wid esp read in the Mesozoic. Leaves to 4 i n . in length.

A Cenozoic l a n d scape with sperms a n d sofl'ie cpnlfers ; very s i m n a r to modern tr.-.

A N G I O S P E R M S a re the fl owe ring p l a nts, w h ich i n c l u d e a b o u t a q u a rter m i l l i o n l i v i n g species. T h e fl ower i s a u n i q u e o rga n . P o l len g ra i n s s p read by i n sects or w i n d p ro d u ce a t u b e by w h ich the e g g c e l l is fe rti l i zed . Seed s a re e n c l o sed a n d p rotected . A n g iosperms develo ped i n t h e C retaceo u s a n d later became s o i m p o rtant that t h e n ew g ra s s l a n d s favo red t h e evo l ution of h o ofed g razers s u c h as h o rses, a ntelope and cattle. A n g i o s p e r m s i n c l u d e the m o n o c ots (Monocotyledons) -g ras ses, l i l i es, s ed g es, palms, p i n ea p p les and o rc h ids, and the d ic ots (Dicotyle足 dons) -p. 1 56 -with s u c h fa m i l ies as t h e ros e,. mal l ow, m u stard , b utterc u p , tomato, m i nt, carrot a n d d a i sy. Fos s i l s o f b oth g ro u ps a re c o m m o n i n f res h -water c l ays, v o l c a n i c a s h a n d oth e r fi n e sed iments. M O N O COTS GRASS, k n own c h i efl y as fos s i l

SAN M IGUEL IA, Triassic, a p a l m 足

seed s, became w i d e s p read i n the M iocene and had a strong i n fl u ence on m a m ma l i a n evo lution. 0.1 in. l o n g seed s.

l i ke p l a n t from C o lorado. If it is a palm, it is the o l d est known a n g io足 s perm. Max i m u m length of leaves about 1 .3 ft.

1 55

O J COTS

MAGNOLIA,

C retaceous to Re cent. A w i d es pread and common b ut very pri m itive a ng iosperm. G rew in A laska and G reenland in late

f. .

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( ali ) , C retaceo u s to Rece nt. Lo n g ( u s u a l l y 3 to 6 i n . ) , s l e n d e r leaves ; e d g e s fi n ely toothed. Common. Fossil pollen is especially i m p o rtant as a m i c rofos s i l . WILLOW

·"

\ I

BIRCH

(Betula ) , C retaceo u s to Recent. W i despread trees. Leaves 2 to 4 in. l o n g , oval, poi nted, edges toothed. Co m m o n fo s s i l s i n d i cating a coo l , tem p erate cl i mate .

(Ficus), Cretaceo u s t o Recent. This fa m i ly, which i n c l udes many tropical fru it trees, i s ty p i cal of warm er reg i o n s . W i d e s p read i n Cenozoic. Leaves 6 to 1 2 in. long.

SASSAFRAS, Cretac eous to Re cent. M e d i u m-sized trees or s h r u b s . Leaves 4 t o 6 i n . i n len gth e i t h e r sim p l e and oval or with 1 to 3 b u l b o u s l o bes. Related t o lau rel.

MAPLE (Acer), C retaceous to Re cent. Med i u m to large trees. W i d e s p read in temperate reg i o n s . Leaves to 1 2 in. in length, broad, lo bed and toot h ed . Fruit w i n ged .

FIG

I N D EX Asterisks (*) denote items which are i l l u strated ; i n d i cates maj o r treatment. A canthe rpestes , 1 02* Acanthosca p h ites, 1 30* Adaptat i o n s , 6*, 7• Aganaster, 1 08* Agelacrin ites, 1 05* A g nathas, 39*, 1 32*, 1 33* A g no stu s , 94* Agon iatites, 1 26* A leth opteris, 1 53* A l gae, 32*, 33, 1 50* A l lorisma, 1 1 8* A m ber, 1 1 * A m blypods, 62*, 63 A m m o n ites, 1 2*, 27*, 51, 53, 59*, 60, 1 23-1 30* A m p h i bi a n s , 40*, 41 *, 44*, 1 39*-140* A m p h i chelyd i a n , 1 43* A m p h i n e u ra , 1 1 0* A n g i os p e r m s , 62*, 63*, 1 55*, 1 56* A n g l a s p i s , 1 33* A n kylosa u rs , 1 45* A n ne l i d s , 92* A rac h n i d s , 34*, 1 02• A rea, 1 21 * A rc haeopteryx, 54*, 1 46* Archelon, 58* Arch i medes, 81 * Arch ita r b u s , 1 02 * A rmad i l l o s , 1 49 Arthrodire, 1 34 A rthrophytes , 1 51 Arthropods, 93*-103* A rtifacts, 1 4* , 71 * A s a p h u s , 97* Astarte, 1 21 * Astero i d , 1 04*, 1 08* Asteroxy l o n , 1 51 * A straeo s p o n g i a , 76* Atrypa, 86* A u stra l o p ithecu s , 71 * A v i c u lopecten, 1 1 9* Bactrites , 1 26* Bac u l ites , 59*, 1 30* Balan us, 1 00* Ba l u c h it h e r i u m , 64*

Ba rnacles, 1 00* Bathyu r i s c u s , 95* Belemn ites, 53*, 1 30* Be l lero p h o n , 1 1 2* B i l o b ites , 86* B i r c h , 1 56* Birds, 9*, 54*, 65, 1 46* B i rken ia, 39* Bivalves, 1 1 6* B lasto i d s , 104*, 1 06* Bo l l ia , 99* Bony fi shes, 1 7*, 40*, 1 32, 1 36-137* B o r i n g s , 1 4*, 92* Bothriolepis, 1 34 * Brac h i opods, 1 1 *, 1 2*, 36*, 42*, 47*, 73*, 82*-91 * Bra n c h iosaurus, 1 40* Brittle sta rs, 43*, 108* Brontops, 64* Brontosau r u s , 55* Bro ntoth e r i u m , 61 *, 1 49* Bryo phytes, 1 51 Bryozoa n s , 36*, 42*, 72*, 81 * B u g u la, 8 1 * B u mastu s , 97* Byssonych ia, 1 1 7* Cacops, 1 40* Calamite s , 44*, 1 52* Callavia, 94* Calymene, 96* Cambria n , 34*-35* Camels, 86* Can i n ia , 78* Carbon i c o la, 1 1 8* Carcharodon , 1 35* Card i u m , 1 22* Ca ryo c r i n ites , 1 05* Casts, 13* Cenozoic Era, 61 *-71 * Cephalaspis, 1 32* Cephalopods, 36*, 38*, 42*, 47*, 73*, 1 1 0* , 1 23*-1 30* Ce ratites , 1 28*

bold face

.C erato p s i a n s , 1 45* Cerith i u m , 1 1 3 * C h aetetes , 78* C h a l i cotheres, 1 49* C h a r n i a , 1 50* C h e i ro l e p i s , 1 37 * C h e l i cerates, 93* C h o a n i chthyes, 1 36, 1 38* C h o n d r i c hth yes, 1 35* C h o n etes, oo• C h o rdata, 1 32*-1 49* Cidaris, 1 09* C l adoselac h e·, 1 35* C l a m s , 1 1 6* C l i macog raptus, 1 31 * C l i mati u s , 1 34* Clypeus, 1 00• Coccosteus, 1 � • C ockroa c h e s , �· o3• C odaster, 1 00• Coelaca n t h u s , 1 38• Coelente rates, 77•-80" Coelodo nta, 69* C o l l e n i a , 32* C o l u m b ites, 1 27* C o m p osita, 90* C o m p so g nath u s , 54* C o n ifers, 1 53, 1 55* C o nocard i u m , 1 1 8* C o nocoryphe, 95* C o n u laria, 92* C o n u s , 1 1 4• C o prol ites, 1 4* Corals, 36*, 38•, 42*, 72*, 11•-ao• C o rdaites, 44•, 1 53, 1 54• C o ry p h o d o n , 62• C reodonts, 63, 64•, 1 47, 1 48• C repi d u l a , 1 1 5• C retaceo u s , 56•-60 C r i n o i d s , 38•, 42•, 43•, 74°, 1 04•, 107• C ro-Mag n o n , 11 • C ru stacea n s , 34*, 93*, 98•-1 oo• C rypto b lastu s , t oo• C ryptocle i d u s , 53• 1 57

C ryptozoon " reef , " 1 50* Ctenodo nta, 1 1 7* Cycadeo i d s , 54* , 56*, 1 53, 1 54* Cycads, 1 53, 1 54 Cymbospondyl u s , 51 * Cynognathus, 47, 50* Cyrtina, 88* Cy rto ceras, 1 26* Cysti p hy l l u m , 79* Cysto i d s , 1 04*, 1 05* Cythere i s , 99* Cythe rel l o i d ea, 99*

....

;::

Dacty l i oceras, 1 29 * Dalmanella, 86*

"' .. Dalman ites, 96* ... � ,._

Dawsonoceras, 1 25*

; Deer, 70*

� Dendrites, 1 8*

....

...

....

� Dendroids, 1 31 *

Denta l i n a , 75* Denta l i u m , 1 1 4* Devo n aster, 1 08* Devo n ian , 40-42* ,._ D iatoms, 1 50* ; Diatryma, 62*, 65 j D icerath e r i u m , 66* i Dicoelosia, 86* ! Dicyn o d o n , 1 42* � D i ctyoclostus, 90'* � .. D i d y m og raptus, 1 3 1 * � Dielasma, 89* " D i kelocephalus, 96* z .. D i metrod o n , 46* � D i n ichthys, 40* .. D i n o h y u s , 66* ; O i n orth i s , 84* D i n osaurs, 1 1 *, 1 3* , 1 4 * , 49* , 50, 52, 54*, 55*, 56* -58, 1 44-1 45* D i n otheri u m , 4* -5* D i p l o c au l u s , 46* , 1 40* D i p l o d o c u s , 20* , 52, 55*, 1 45* D i p l o g raptus, 1 31 * D i p l overtebron, 1 40* D i pterus, 1 38* Dizygopl e u ra, 99* Dolatocri n u s , 42* Dolorthoceras, 1 25* D rag onflies, 44*, 1 03* D repanas p i s , 1 33*

" z .. .."' �

1 58

Drepanella, 98* D u n barel la, 1 1 8* Echi noderms, 1 04* E c h i n o i d s , 74*, 1 04* , 109* E c h i n o s p h aerites, 1 05* Edaphosaurus, 1 41 *, 1 42* Edentates, 149* Edrioasteroids, 1 04 * , 105* Elephants, 4*-5*, 10*, 69* Elk, 70* E l rath ia, 94* E m b ryophytes, 1 51 * Endoceras, 36*, 1 24* Ensis, 1 22* Enteletes, 91 * Eocene, 1 7*, 62, 64, 1 48*, 1 49 Eod i s c u s , 95* Eogyri n u s , 1 40* E o h i p p u s , 62-63*, 67* Eospir ifer, 86* E q u u s , 67* E ras, geologic, 30*-31 * E ryon, 1 00* E ryops, 46*, 1 39* E u rh i nosaurus, 52* E u rypteri ds, 38* , 101 • E u s m i l ia, 80* Eusth e n o pte ro n , 40* , 1 38* Evolution, 4*-9* , 30-31 * , 67*-68, 1 23*, 1 42* , 1 43*, 1 55 Exogy ra, 1 20* Favosites, 38*, 78* Fen estrel l i n a , 81 * Ferns, 41 * , 44*, 153* Fig, 1 56* Fish, 8*-9*, 1 7*, 37*, 39*, 40*' 65, 1 32-138* Flexicalymene, 36*, 96* Foram i n ifera, 65 , 75* Fossi l s : collecting, 1 9* -26* defi n ed , 1 0 index, 21 * p reservation, 1 0*-15* F u s u s , 1 1 4* Gastrioceras, 1 26*

Gastro l it h s , 14* Gastro pods, 36* , 38* , 42* , 59* , 73*, 1 1 0*-1 1 5* Geologic time, 28-31 * G i n kgos, 54, 1 53 , 1 54* G l o bigeri na, 75 * Glycimeris, 1 21 * G l y ptoc r i n u s , 1 07* G l y ptodont, 6 * , 70, 1 49* G l y ptopl e u ra , 99* G o m p hoceras, 1 24* G o n iatites, 1 27* G o n ioph o ra, 1 1 7* Grammysia, 1 1 7* Grand Canyon, 1 5* , 28* Grapto l ites, 74* , 1 31 * Grasses, 66, 1 55* Griffith ides, 97* G r o u n d S l oth, 1 47*, 1 49* G ryphaea , 1 20* G y m n osperms, 153*-1 54* Halysites, 38*, 79* Ham ites, 1 28* Hebertella, 84* H e l i oceras, 59* Hem icystites, 1 05* Hespero r n i s , 59, 1 46* Hexacora l , 78* H i l d oceras, 1 28* H i p purites, 1 21 * H o l optyc h i u s, 1 37* H o l oth u r o i d , 1 04* H o m o h a b i l i s , 71 Ho rmotoma, 1 1 1 * Ho rse, 62-64*, 66, 67* , 68, 148, 1 49* H u d sonaster, 1 08* H u g h m i l l eria, 1 01 * Hyaenod o n , 64* H y d n oceras, 76* Hypse l o c o n u s , 1 1 1 * H y racoth eri u·m , 62-63*, 67* I c hthyosaurs, 51 , 52* , 53, 1 43* l chthyostega, 40* , 41 *, 1 39* I n ocera m us, 60, 1 20* I n sects, 1 1 *, 44* , 93*, 103* I ri s h E l k, 70* l s o c ri n u s , 1 07

l sotel us, 97*

J amoyti u s , 39* Jawless fi s h , 39* , 40, 132*, 1 33 * Jellyfish, 33* , 34* , 77 J u ras s i c , 52*-55* J u resa n i a , 91 * Kirkbyel l a , 99* Labyrinthodont, 44* , 1 39*, 1 40* Lacew i n g , 1 03* Lamel l i b ra n c h s , 1 1 6* Lamp s h e l l s , 82• Leba c h i a , 1 54* Leperd itia, 98* Lepidocy c l u s , 85* Lepid odendron, 44* , 1 52* Lepidotu s , 1 37* Leptaena, 88* Lima, 1 1 9* L i n g u la, 82* , 88* L i n g u l e l l a , 82* L i n o p r o d u ct u s , 91 * Lithostroti o n , 79* Littorina, 1 1 5* Lobe fi n s , 1 36, 1 37*, 1 38• Lophop h y l l i d i u m , 79* Love n ec h i n u s , 1 09* L u n g fi s h , 1 38* Lycopod s , 4 1 * , 44* , 1 52* Maclu rites, 1 1 1 • Madrepo ra, 78* Mage l l a n i a , 83* M a g n o l i a , 1 56* M a m m a l s , 9*, 53, 57, 59 , 61 *-71 * , 1 47*-1 49* Mammoths, 1 0* , 69* Man, emergence, 7 1 * Maple, 1 56* Marg i n ifera, 91 * Mastod o n s , 5*, 66* Meekoceras, 1 27* Meganeu ra, 44* Megathe r i u m , 1 47* Meristina, 87* Merych i p p u s , 67* Meso h i p p u s , 64 * , 67* Meso l o b u s , 90* Mesopal easter, 1 08*

Mesopsychopsis, 1 03* Mesosa u r u s , 47* Mesozoic Era, 49"'�60* M i c raste r , 1 09* M i c rofos s i l s , 21 , 76* M i l lepedes, 1 02• M i ocene, 66*-68 M i ss i s s i p p i a n , 43* M o d i o l o p s i s , 1 1 7* Moeritheri u m , 5* M o l d s , 1 3* M o l l u sks, 59* , 1 1 0*-130* M o n o g raptus, 1 31 * M o ntivaltia, so• M o r o p u s , 66*, 68, 1 49* M o sasau rs, 58* , 1 43* M o s c h o p s , 1 42* Moss agate, 1 8* Moss a n i ma l s , 81 * M u crosp i r ifer, 89* M u ensteroceras, 1 23*, 1 27* M u rch i s o n ia, 1 1 3* Myali na, 1 1 8* M y riapods, 1 02* Natica, 1 1 5* Nauti l o i d s , 27*, 1 23*-1 30* Nean dert h a l , 71 * N e m a g raptus, 1 3 1 * N e o l e n u s , 34* Neospi rifer, 90* Neozaph rentis, 79* N e rei s , 92* N e r i n ea, 1 1 3* N e u ropte r i s , 1 53* Notharct u s , 62* Nothosa u rs , 1 43* Nothrotheri u m , 1 49* N u cu la, 1 1 9* O b o l e l l a , 82 * Octocoral, 78 * Octo p u s , 1 23 * O g y g o p s i s , 95 * Olenel l u s , 94* O l e n o i d e s , 35* O l igocene, 62, 64* O p h iacod o n , 1 42* O p h i u ro i d , 1 04*, 1 08* O r b i c u l o idea, 89* Ordov i c i a n , 36*-37* Oredonts, 64*, 65

O r n it h o p o d s , 1 45* O r n ith i s c h ia n s , 1 44, 1 45* Ostei chthyes, 1 36-1 37* Osteo l e p i s , 1 37* Ostracoderms, 37* , 1 32* Ostracods, 98*-99* O strea, 1 21 • Oxyaena, 1 48* Oysters, 59* Pachyteuth i s , 1 29 * Palaeo p h o n u s , .102• Paleocene, 62, 1 48* P a l eozoic E ra, 34*-48 P a l m s , 62*, 63*, 1 55* Paradox i d e s , 95* Paral l e l d o n , 1 1 9* Pecte n , 59* , 1 22• Pelecypods, 36* , 59*, 73* , 83* , 1 1 0*, 1 1 6*-1 22* P e n n s y l v a n i a n , 44*, 45* Penta m e r u s , 87* Pentremites, 1 06* Perm ian , 46*-48* Petrified wood, 1 2• Petrocra n ia, 85* Phacops, 97* P h enacod u s , 1 48* P h o rorhacos, 1 46* P h ragm oceras, 1 25* P h ytosa u r , 50* P i g s , 66* P i n na, 1 20• Pithecan t h r o p u s , 71 * Placoderms, 40* , 1 34* Placodonts, 1 43* Placod u s , 51 * P l a n o rb u s , 1 1 5* P l a nts, 7*, 38, 41 * , 44* , 54, 56*-57*, 63* , 1 50*-1 56* P latyce ras, 1 1 2• P l atyc rin ites , 1 07* P latyostoma, 1 1 2* P l atystro p h i a , 85* P l e i stocene, 69*-70 P l e s i o sa u rs, 51 , 52* , 53 , 1 43* P l e u rocanth u s, 1 35* P l e u roto maria, 1 1 3* P l iocene, 66-68 P l i o h i p p u s , 67* Po l yg y ra, 1 1 4* 159

Porifera, 76' P re-C a m b r i a n , 32*-33*

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Pri mates, 62*-63, 71 ' P rota p i ri s , 64* P roto z o a n s , 75* Pseu d ofo s s i l s , 1 8' P s i l o p hyton , 41 ' P s i l o p s i d s , 1 51 * Ptera n o d o n , 57' , 58* Ptera s p i s , 1 33' Pteria, 1 1 9* Pterichthys, 1 34 * Pte r i n ea, 1 1 7* Ptych o paria, 95'

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Q u ate rna ry, 69*-71'

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Rad i o laria, 75' Rafi n e s q u i n a , 36*, 84* Rays, 1 35 * Receptac u l ites, 76* Reconstruct i o n , 4* , 27* Rept i l es, 8'-9', 45*-58, 141 *-145* R h a m p h o rh y n c h u s , 54* R h i noceros, 64*, 66*, 69*, 1 48 R h o m bopora, 81 ' R h y n c h o n el l a , 91 ' R h y n c h otreta, 87* R h y n i a , 1 51 * Saber-toothed cat, 64, 65, 68, 70' Sagen ite s , 1 28' Sail-backed l i zard, 46' S a n m i g u e l ia , 1 55' Sassafra s , 1 56' S a u r i s c h i a n s , 1 44, 1 45' S a u ro p o d s , 55*, 56', 1 45' Scale trees, 41 , 44' Scallop, 1 1 ' Scaph ite s , 1 23' 1 30* S c a p h o p o d , 1 1 0' , 1 1 4' S c h izo b l a stus, 1 06* S c h i z o c o ral, 78* S c h u c h e rtel la, 87* Scolecodonts, 92' Scorp i o n s , 93, 102* S c o u r i n g rushes, 41 *, 1 5 1 , 1 52' Sea a n em o n e s , 77* Sea l i l i e s , 107* Sea u r c h i n s , 1 04* , 1 09' 160

Sed i mentary rocks, 1 5*- 1 7 * , 28 Seed ferns, 4 1 * , 44', 1 53* Serp u la, 92* Seymo u ria, 46*, 1 41 ' Sharks, 40*, 135* S h r i m ps, 1 00' S i g i l l a ria, 44* , 1 52* S i l u r i a n , 38*-39' Skate s , 1 35' S loth s , 70, 1 49' S m i l o d o n , 70' S p h e n o p h y l l u m , 1 52' S p h e n o p s i d s , 44', 1 52' S p h e n opteris, 1 54* S p i ders, 1 02' S p i rifer, 89' Sponges, 34', 47', 76* S q u i d s , 53* , 1 23' Sta rfi s h , 38*, 1 04', 1 011• Stegosau r u s , 55* , 1 45* Ste n o m y l u s , 66' Ste p h a n oceras, 1 29' Stigmaria, 1 52' Straparo l l u s , 1 1 2' Strata, 1 5 * , 21 ' Strepte lasma, 36*, 79* Stromato p h o r o i d , 78' Stro p h eodo nta, 88' Stro p h omena, 85* Struth i o m i m us, 56-57' Sty laster, so• Stylemys, 64' Sty l o n u ru s , 1 01 * Syri n g o p o ra, 79' T a b u l ate coral, 78' Tapi rs , 64* , 1 48 Tarso p h l e b i a , 1 03' Taxo c r i n u s , 1 07* Tenta c u l ites, 92* Tertia ry : Lower, 62*-65* U p per, 66*-68 Tetracora l , 78' T h a l l o p h ytes, 1 50' · T h a m n asteria, so• Thecodonts, 50' , 1 45* T h e l o d u s , 1 33' The ropods, 1 45 ' T itanothe res , 61 * , 64*, 65, 1 49' T rac h o d o n , 56-57' Tree fern s , 41 '

T rees , 54, 56*-57* , 63*, 1 54*, 1 55 * - 1 56* Triassic, 50* -51 * T r i cerato ps, .26' , 56* T r i g o n i a , 1 1 9' T r i l o bites, 34'-38*, 42', 74' ' 93'-97' T r i l o p h o d o n , 5* , 66* T r i n u c l e u s , 96' T u d itan u s , 45* T u rril ites, 1 29' T u rrite l l a , 59' , 1 1 3' Tu rtles, 58', 64', 1 43' Ty losa u r u s , 58* Tyran o s a u r u s , 49* , 56, 57*, 58 U i ntath eres, 63' , 1 48' U ng u lates, 148* U n i o , 1 22' U rastere l l a , 1 08' Vasc u l a r pla nts, 1 5 1 * - 1 53 Ventr i c u l ites , 76' Verteb rates, 8'-9* , 37', 40* , 4 1 * , 44*-71 * , 1 32*-149* Vertigo, 1 1 5* V i v i p a r u s , 1 1 4' V o l uta, 1 1 4* W i l l i a m s o n i a , 1 54* W i l l o w , 1 56* Woo l l y mam moth, 69' Wool l y rh i n oceros, 69' W o r m s , 1 1 * , 33*, 34*, 92* W o rt h e n i a , 1 1 2' Z i n j a n t h ro p u s , 71 Zyg o s p i ra, 84 •

A GOLDEN NATU RE GUIDE FRANK RHOD ES, P h . D., has done extensive field study in Europe a n d i n North Am erica. He ha s worked on resea rch problems i n the Rock ies and has taught for several years a t the U n iversity of I l l i nois. He is the a uthor of The Evolution of Life and many tec h n i c a l papers. At p resent he is Professor of Geology, U n iver sity of Wa les at Swa nsea. H E R B ERT S . ZIM, P h . D . , ou tsta n d i n g a ut h o rity on science educati on a n d formerly P rofessor of Education, U n ivers ity of I l l i n o is, is w e l l known i n professi o n a l c i r c l es a n d to a wide rea d i n g p u b l i c . H e i s co-author of the Golden Nature G u i des: Birds, Flowers, Insects, Sta rs, Trees, Reptiles and Amph ibians, Ma m m a ls, Seasho res, Fishes, Weather, Rocks a n d Min erals, Gameb irds, Fossils, a n d Zoology. PAUL R. SHAFFER, P h . D . , Professor of Geology a t the U n iversity of I l l in ois, has written m a n y g eologica l pa pers f o r scientific j o u r n a l s . H i s academic a n d industri a l work takes h i m into most region s of the U nited States, studying a n d c o l l ecti n g . RAYMOND PERLMAN is a Professor of A r t at the U n i versity of I l l i n ois. He holds deg rees i n fi n e a rts from that u n iversity, a n d i s a Master of Profess i o n a l Arts from the Art Center School i n los Angel es. He has designed a n d i l lus trated many books o n sci e n c e .

FOSSI LS Here is a fi e l d g u ide to the fascinating study of fossi l s . Typ ica l p l a n t a n d a n i m a l l ife of t h e m a j o r periods o f g e o l o g i c time a re s h o w n i n c o l o r , a n d c o n cise t e x t describes representative foss i l types of these periods. FOSS I LS, a Golden N ature Guide, g ives you m a p s w h i c h show t h e g e n e r a l a reas where fossi l s may be f o u n d , p l u s s c o r e s o f f u l l c o l o r i l l u strations of common fossi l spe c i m e n s to h e l p you identify yo u r fi nds. Foss i l re m a i ns, p r i n ts, a nd other i n d ications of former plant a n d a n ima l l ife te l l the l o n g a n d i n te resti n g story of the de足 ve lopment of l ife o n earth. Evo l u ti o n a ry stages a re treated from the Pre-C a m b i a n to the Recent. With 48 1 f u l l-c o l o r i l l ustrations a n d m a p s .