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"dinosaurbook

By EDWIN H. COLBERT THE AMERICAN MUSEUM OF NATURAL HISTORY FOR THE PEOPLE FOR EDVCATION FOR SCIENCE

LIBRARY OF THE AMERICAN MUSEUM OF NATURAL HISTORY ^

the dinosaur book

th e

book the ruling reptiles and their relatives

By Edwin H. Colbert

Curator of Fossil Reptiles, Amphibians, and Fishes The American Museum of Natural History

Illustrated by JOHN C. GERMANN

Staff Artist

With additional illustrations, previously published,

by Charles R. Knight and others

MAN AND NATURE PUBLICATIONS

HANDBOOK No. 14

Published by THE AMERICAN MUSEUM OF NATURAL HISTORY

New York, N. Y. 1945 u Copyright, 1945, by

The American Museum of Natural History

Copyright under the Articles of the Copyright Convention of the

Pan-American Republics and the United States

<

Printed in the United States of America

By George Banta Publishing Company, Menasha, Wisconsin TO WILLIAM KING GREGORY TEACHER, AUTHORITY ON FOSSIL AMPHIBIANS AND REPTILES, AND PROFOUND STUDENT OF VERTEBRATE EVOLUTION

Prefa ce

or many years there has been felt the as this. To all readers, whether they have ^ need for a popular guide book on the access to the Museum or not, it is felt that fossil amphibians and reptiles, with restorations give a more graphic picture particular attention given to the dinosaurs. and convey more information than do Dinosaurs by W. D. Matthew, published skeletons, the bones of which are un- by the American Museum of Natural His- familiar to most people. Therefore much tory in 1915, has long been out of print. attention has been given to the restorations Animals of the Past by Frederic A. Lucas, used. All of the new restorations have been also published by the Museum, has gone made by Mr. John C. Germann, and to through many successive editions and print- him goes much of the credit for any favor-

ings, and is in constant demand. This ex- able impression that this volume may cellent book does not, however, answer the create. In addition, certain of the well- demand for a complete story about the known restorations by Mr. Charles R. dinosaurs and other fossil reptiles and Knight have been repeated; they are amphibians, since only three of its four- worthy of constant repetition for no better teen chapters are concerned with extinct impressions of some of the former denizens reptiles. of our land have ever been created.

Consequently it was decided a year or Several people have aided the author in so ago to write this book, now appearing bringing this book to successful completion. for the first time. It is written to fill a Special acknowledgments are due to Pro- definite need, namely to tell the story of fessor William King Gregory of Columbia amphibian and reptilian evolution. University and the American Museum of

The book is written to supplement the Natural History, to Professor Alfred S. displays of fossil amphibians and reptiles in Romer of Harvard University, and to Mr. the American Museum of Natural History, Charles M. Bogert of the American but it is written in such a way that it may Museum of Natural History. These eminent be used by anyone interested in the subject, authorities were all kind enough to read whether he has access to our Museum halls the manuscript and to offer criticisms and or not. Therefore it is written in general suggestions. terms, and references to particular skeletons The manuscript was typed by Mr. Louis or fossils on display are omitted. To the A. Monaco, who gave many suggestions museum visitor, the label will identify the that were helpful. display. Moreover, the animals described Finally, particular credit for making this in this book are illustrated by restorations book what it is should go to Dr. Edward showing their appearance in life, rather M. Weyer, Jr., the editor, and to Mr. than by photographs of skeletons on dis- Frederick L. Hahn who supervised the play. To the museum visitor the actual layouts. fossils are at hand, so it is superfluous to repeat them with pictures in a book such Edwin H. Colhert

Contents

Preface 7

1. Introducing the Dinosaurs 11

2. Pioneer Students of the Dinosaurs 15 List of North American museums housing collections of fossil reptiles and amphibians 24

3. Hunting Dinosaurs 25

4. The Age of Reptiles 36

5. The First Land Animals 41

6. Primitive Reptiles 47

7. The Mammal-like Reptiles 53

8. Ancestors of the Dinosaurs 60

9. The Kinds of Dinosaurs 64 Saurischia 68 Ornithischia 73

10. Adaptations of the Dinosaurs 84

11. Dinosaurian Associations 94

12. Flight 97 Pterosauria 97 The Birds 100

13. Sea Serpents 104 The Ichthyosaurs 105 The Euryapsida 110 The Mosasaurs 112 The Marine Crocodiles 114 14. Decline of the Dinosaurs 115

15. The Survivors 118 Crocodiles, Ancient and Modern 118 The Long-Persistent Rhynchocephalians 121 The Lizards and Snakes 122 The Turtles 123

16. Why Study Fossils? 125

17. Where the Dinosaurs and Their Relatives Are Found 127

18. How the Dinosaurs and Their Relatives Are Classified and Named 133 Synoptic Table of the Amphibia and Reptilia, including the Genera Mentioned in this Book 138

19. Other Sources of Information 142

Index 145

10 Introducing the Dinosaurs

Almost everybody knows that at one around him. Fossil skeletons are to be seen time, long ages ago, there were dino- in the exhibition halls of many of our larger saurs on the earth. Indeed, the pub- museums. Here also are pictures showing lic has become "dinosaur-conscious"—so what these ancient animals looked like much so, that the word "dinosaur" has be- when they were alive. And from the mu- come a common term in the English lan- seums they get into books of various kinds. guage, a word that stands for strength, size, Now and then a dinosaur will show up and antiquity. on the Broadway stage or at a World's Fair.

And it is no wonder that the average They are constantly popping out at us in man has at least a slight nodding acquain- humorous cartoons, and they frequently tance with the dinosaurs, for in these days come to life in the movies. Their remains of widely disseminated thought they are all and the tracks they made can be seen

11 in various localities throughout North America; one famous dinosaur collecting ground has been made a National Monu- ment just so that visitors can see how dinosaurs are discovered and excavated from the ground. Modern man, whether he

wants to or not, is sooner or later going to run into a dinosaur or something having to do with dinosaurs.

Reproduced by special permission from Thr Saturday Evening Post. Not in the way that the cave men are Copyright 1939 by the Curtis Publishing Company sometimes portrayed as meeting the dino- 'It's hard to believe we're made like that inside!" saurs, with club or spear. No cave man ever saw a dinosaur. No human being ever met one alive, for the dinosaurs disappeared from the face of the earth millions of years

before the first men appeared. Yet this idea of man and the dinosaurs living together at

one time does persist, and it illustrates one of many misconceptions that are common with regard to the dinosaurs.

Indeed, so persistent is this idea that

Reproduced by special permission of The Saturday Evening Post. Copyright 1940 by the Curtis Publishing Company

*'I don't mind you boosting your home state, Conroy, but stop telling the children that dinosaur is a California jack rabbit!"

Leonard Dove, in Collier's Wi',kh "We had seven hundred natives excavating the ruins, but you'll never guess who found it."

«-

i opjrrighted. Reprinted permission Tha New Yorktt

"And here is my first dinosaur—makes me feel like a kid again every time I look at it." there are periodic outbreaks of sensational stories having to do with dinosaurs that

are still living in some far corner of the South American jungles. Sir A. Conan Doyle's romantic novel The Lost World was based upon this idea. And no matter how

often this misconception is killed by

scientific facts, it keeps coming to life.

Another misconception is the common

one that dinosaurs were all tremendously large beasts, crashing through the strange forests of an ancient world and tearing up

trees by the roots. It is true that many of the dinosaurs were large, and some of them were the greatest animals ever to walk

across the land, but it is equally true that there were many medium-size and small dinosaurs. What, then, are the facts about dino- saurs? How did they live? What did they eat? How did they reproduce? What kinds

Copyrighted. Reprinted permission The New Yorker "Take a telegram to the Museum of Natural History." DINOSAURS IN THE PUBLIC EYE

a *>i^j

By Henry Boltinoff in Maclean's

William Hayes in Collier's Weekly "Homer told me before we were married he was a paleontologist.

Adds a little life to the old place, don't you think?" But I didn't know what it was!"

13 of enemies did they have, and how did It is the purpose of this book to present they succeed in ruling the earth for so a picture of the various kinds of dinosaurs, many millions of years? This seems like a to explain their relationships to one another lot to ask about animals that no one ever and to other reptiles, to inquire into the saw alive, yet the answers to these questions manner in which they lived together, and have been pretty well worked out through to explore the environmental conditions the scientific detective work that has that surrounded them and determined the brought us to our present rather complete separate courses of their varied life his- knowledge as to the anatomy, the habits, tories. Since there were other reptiles living and the environment of the dinosaurs. with the dinosaurs, the picture cannot be

They are oft-repeated questions, too, for thoroughly understood unless it is com- the subject of dinosaurs is a fascinating one pletely presented, so these contempo- to a very great many people. raneous animals will also be described, and

Let us therefore get acquainted with the their places in the general scheme of life dinosaurs in a proper way, let us learn to will be evaluated. Finally, since the dino- know them instead of continuing to look saurs came from earlier reptilian ancestors, at them from across the street. the primitive reptiles of earlier ages will be The dinosaurs were reptiles, cold-blooded discussed, while the ancient amphibians, animals related to the crocodiles, lizards, the ancestors of all four-footed animals and snakes. They lived during the Mesozoic will also be considered. In short, this will period of Earth History, which began some be a story of the evolution of vertebrate life

200 million years ago and ended about 60 on the land as it occurred between the million years ago, at which time the dino- emergence of the first land living animals, saurs became extinct. The dinosaurs were the amphibians, from their fish ancestors, of many kinds, some being of tremendous some 340 million years ago, to the final size, some small, some adapted to a car- culmination and the ultimate decline of nivorous or meat-eating mode of life, some reptilian dominance, almost 300 million to an herbivorous or plant-eating existence. years later.

Large or small, meat-eating or plant-eating, It is a story of great proportions, stretch- the dinosaurs were dinosaurs by virtue of ing over long periods of Earth History. their anatomical structure—a subject that It is a story on so vast a scale as to dwarf will be explained in more detail at another our own history almost to insignificance. place in this book. They were the ruling Yet great as are its dimensions, it is a storv land animals of Mesozoic times, and con- that is finished, for it is a tale of the triumph sidering the great duration of the stage in of brawn, a triumph that was long-lived,

Earth History through which they lived but which in the end gave way to the they must be considered as among the most triumph of brain. The dinosaurs had their successful of the backboned animals. day, and while it lasted it was a Great Day.

14 Pioneer Students of the Dinosaurs

hundred years or so ago the science quarrymen. Thus began the pioneer period

/\ of paleontology was in its infancy. in the science of paleontology, the period There were no well-established tech- when the study of fossils became a well- niques for the discovery and excavation of founded full-time subject of investigation

fossils, and the study of ancient life on the by serious, trained scholars, rather than an earth was carried on in a rather haphazard avocation for gentlemen of broad interests. manner. Fossils were to a great extent the The outstanding figure of the pioneer

result of accidental finds. Some quarrymen period was Baron Georges Cuvier, the great would turn up a strange object while work- French anatomist and paleontologist. ing out roofing slates or building blocks or Cuvier (1769-1832) became interested in road material; this strange object would be Natural History at an early age, and by the regarded with a suspicious eye, argued beginning of the nineteenth century he was

about, and finally presented to the nearest established as Professor of Natural History available "professor" for identification. Per- at the College de France. From about 1798 haps the professor would not be able to until the time of his death he applied him-

place it, in which case he would pass it self diligently to the study of fossil verte- along to another professor until finally the brates (backboned animals), publishing fossil, usually a pitifully small fragment, many important papers and memoirs on the would come to rest in the collection, or the comparative anatomy and the classification

"cabinet" (as museums were then called), of the vertebrates—both living and fossil. of some college or university or learned so- As a result of his labors the inter- ciety. Fossil collections were largely the re- relationships of the backboned animals sult of chance, and the study of fossils was and the unity of their basic pattern were therefore for the most part opportunistic. for the first time adequately elucidated to Naturally, the existing knowledge of past the scientific world. He may be said to life on the earth was very spotty and in- have been the founder of the science of complete. Vertebrate Paleontology. Since knowledge of past life was incom- A contemporary of the great Cuvier was plete, its interpretation was inadequate. Dr. Gideon Mantell (1790-1852), an Eng- But as men became more and more inter- lish physician, who during the early part ested in the history of the earth they be- of his life lived at Lewes, south of London. came more aware of the fact that the Doctor Mantell became interested in fossils chance collection of fossils and their chance to such an extent that he turned with vigor study would hardly suffice to give a true to the excavation and study of extinct understanding of the development of an- animal life as it was preserved in the cient life. Consequently the subject began Wealden or lower Cretaceous sediments to attract serious students, who based their around Lewes. He justlv attained eminence work on materials avowedly collected for as a student of geology and paleontology study—not upon the chance discoveries of through the important discoveries that he

15 GREAT PIONEERS IN NATURAL SCIENCE

Engraved by C. E. Wagstaff The great Swedish botanist Linnaeus (1707- Georges Cuvier (1769-1832) won lasting

1778) originated the system that is still used fame by revealing the relationships among for naming and classifying all plants and backboned animals, particularly as shown by animals their skeletons

Richard Owen (1804-1892), outstanding Charles Darwin (1809-1895) revolutionized authority of his time, coined the name Dino- scientific thought throughout the entire field saur'ia and established the study of extinct of natural history and ranks as one of the animals on a scientific basis in England world's greatest students of Life

16 made and the lucid papers that he pub- these extinct reptiles needed a name to lished, describing and interpreting his designate them, and it was he who coined finds. Perhaps Mantell's chief claim to fame the word Dinosauria. Subsequently Owen's was his discovery and description of name became anglicized to dinosaur, and

Iguanodon, the first dinosaur to be found in today it has acquired an established place England. Indeed, his paper on Iguanodon, in our common language. published in 1825, established Mantell as Strange as it may seem, one of the first the pioneer student of the dinosaurs in excavators of fossil reptiles (although the England. objects dug up were not dinosaurs) was not In Lewes the house of Gideon Mantell a learned student of paleontology but a is still standing, and on a brass plate young girl. fastened outside the door of this house are Mary Aiming lived at Lyme Regis in these words: southern England with her father, in the early days of the last century. In those days "He discovered the Iguanodon" many people from London sought the fresh

However, the greatest of the early Eng- airs of the seacoast, and Richard Aiming lish students of dinosaurs and other extinct made a small living by collecting fossil sea- animals was Sir Richard Owen (1804-1892). shells and selling them to the tourists. In If Cuvier may be called the founder of the this interesting trade he was aided by his science of vertebrate paleontology, Owen daughter, Mary, who may be said to have may be called the man who established the been an early protagonist of the old tongue- science in England. Like so many early twister—"She sells sea-shells." students of Natural History, Owen pre- When she was a little girl, but twelve pared himself for the practice of medicine, years old, she discovered, while searching but by the time he had completed his for fossil shells, the first skeleton of the medical studies it became apparent to his marine fossil reptile, Ichthyosaurus. That professors that he was much too valuable was in 1811. She became interested in the a man to go into general practice. So he fossil reptiles of the marine Jurassic beds turned to anatomical research and in due of southern England, and from that time on course of time became Hunterian Professor she was ever on the lookout for skeletons. at the Royal College of Surgeons. However After the death of her father, Mary Anning Owen's interests ranged far beyond the continued the business of collecting fossil field of human anatomy, and he became by shells for the tourist trade, but her real virtue of his investigations the outstanding interest was in the bigger vertebrate game. authority of his time on the anatomy of the To make a long story short, she embarked backboned animals, both living and extinct. upon a career of fossil reptile collecting,

He was the first Director of the Natural and she made good in a field that has been History division of the British Museum, since its beginnings a man's game. In 1821 and was instrumental in establishing this she found the first Plesiosaurus skeleton, institution in its present buildings in the and in 1828 she discovered the first skeleton

South Kensington district of London. of a pterosaur, or flying reptile, to be un- Many of Owen's studies were on dino- earthed in England. She collected numer- saurs. It was he who first recognized that ous fine specimens of ichthyosaurs and

17 plesiosaurs and sold them to various indi- Hitchcock may be considered as one of the viduals and institutions throughout the first collectors on this continent of dino- world. saurian remains (or at least the evidences Some mention should be made at this as to the existence of dinosaurs), even place of Charles Darwin (1809-1882) and though he at first did not realize the sig- his great disciple, Thomas Henry Huxley nificance of his finds. Of course Hitchcock's

(1825-1895). Darwin, who must rank as one mistake is readily understandable, when it of the greatest men of all time, was not is remembered that in his day dinosaurs primarily a student of fossil reptiles, or of were virtually unknown and when it is dinosaurs in particular, but it was his con- realized that the tracks he saw, those of cept of organic evolution that revolution- two-legged dinosaurs, closely resemble ized scientific thought throughout the en- large bird tracks. tire field of Natural History. Since the However, the first dinosaur skeleton to publication of Darwin's Origin of Species be discovered in North America was found, in 1859, man has come to look at dinosaurs of all places, in a suburb of Philadelphia, and all other remains of extinct life in a the little town of Haddonfield, New Jersey. very different light than he had previously The fossil first came to light during the viewed them. Our modern understanding course of some excavations in a marl bed, of the development of life on the earth is and it immediatelv was an object of based upon Darwin's work; our philosophy curiosity to the diggers, to their sisters and has grown from the stem of Darwin's great their cousins and their aunts, and to the philosophical truths. Of all the great stu- public in general. As more bones of the dents of Life, Darwin was the greatest. animal came to light they were carted off Huxley worked ably and hard in the as souvenirs, so that many of them came to years following the publication of the rest on New Jersey mantelpieces, or served Origin of Species as a champion of Dar- as doorstops in Pennsylvania homes. winism. He was a brilliant scholar. He de- Some vears later, in 1858, this discovery voted considerable attention to fossil came to the attention of Mr. W. Parker reptiles. Foulke, a Philadelphian interested in the At about the time that Cuvier and subject of Natural History in general and Mantell were working in Europe, some in the Philadelphia Academy of Natural queer, three-toed tracks were being found Sciences in particular. Mr. Foulke re- in rocks of Triassic age, in the Connecticut opened the excavation where the fossil had Valley. They excited the particular interest been partially disinterred, and he found a of Professor Edward Hitchcock, of Amherst great deal more of the skeleton.

College. He collected and studied examples The skeleton, or such of it as still re- of the fossils, many of which are still to be mained, was placed by Mr. Foulke in the seen in the collection of the Amherst Col- Philadelphia Academy of Natural Sciences, lege Museum, and he came to the con- where it was studied by the American clusion that these tracks had been made by paleontologist and anatomist. Dr. Joseph some large, extinct birds. Later it was Leidy (1823-1891). Leidy, a man of great realized that these were actually tracks of ability and learning, may be said to have early dinosaurs and other reptiles, so that been the founder of the science of verte-

18 FOUNDERS OF MODERN FOSSIL EXPLORATION AND RESEARCH

Joseph Leidy (1823-1891) inaugurated the Edward Drinker Cope (1840-1897), of period of continuous research in vertebrate Quaker ancestry, was a leading pioneer in the paleontology in North America search for fossil animals in our West

Othniel Charles Marsh (1831-1899) had a Henry Fairfield Osborn (1857-1935) organ- genius for organization and led many fossil ized vertebrate paleontology on its modern hunting expeditions into western North basis with a staff of highly trained experts at America. He and Cope were scientific rivals the American Museum of Natural History

19 brate paleontology in North America; it scholars that this country has ever pro- was from the beginnings he made in the duced. He was of Quaker ancestry, the subject that the science has continuously descendant of an old and prominent Phila- developed and grown to its present stature delphia family, yet in spite of his many in this country. He was for many years gifts of position, wealth, and intellect he Professor of Anatomy at the University of was a person of erratic temperament, a Pennsylvania and in addition served on the fact which conditioned many of his actions scientific staff of the Academy. While work- in later life. ing on this fossil, Leidy was able to trace Othniel Charles Marsh (1831-1899), a down some of the "souvenirs" and add them man of perhaps lesser intellect than Cope, to his skeleton, although, unfortunately, was nevertheless a scholar of ability with a many of the vertebrae and other parts first genius for organization. Like Cope, Marsh discovered were irrevocably lost. Neverthe- was a man of considerable wealth. less, the better part of the skeleton was At first Cope and Marsh were friends, obtained. It is the skeleton of a duck-billed but when their work began to reveal the dinosaur, Hadrosaurus. fossil wealth of the West, they soon became In spite of the good work of the pioneer rivals, and eventually bitter enemies. Thev paleontologists during the first half of the organized their own expeditions to collect nineteenth century, there was then no con- fossils. Year after year, during the quarter- certed program of fossil collecting in North century between about 1870 and 1895, America. This phase really began after the Cope and Marsh had exploring parties in War Between the States when the great the field, delving into the virgin fossil lo- expanses of the West were being opened. calities of the great Plains and of the Rocky At that time the United States Government Mountain basins. It was a race to see who instituted a series of "Territorial Surveys" could get the most material and describe of the West, in an effort to assess after a it—a race that now seems fruitless, since we fashion the natural resources of the strange have come to learn how abundant are the new land. The emphasis of these surveys fossils to be found by the trained and dili- was on the geological side, and a result was gent fossil hunter. There is enough ma- the discovery of many fossil localities. terial for everybody. But Cope and Marsh Arrangements were made whereby the didn't think so, and they engaged in a fossils would be studied by two men who cutthroat competition which was perhaps had independently begun to conduct and one of the bitterest scientific feuds in his- direct some ambitious collecting trips in tory. The result was that both men pub- the western territories. These men were lished a great deal, much of which was Edward Drinker Cope of Philadelphia, and good, some of which was bad; and two Othniel Charles Marsh of Yale University, great fossil collections were built up. And and with them there began a new, inter- in these collections dinosaurs loomed large. esting, and highly exciting period in It was the first attempt at large-scale,

American paleontology. long-term, planned collecting of fossil Edward Drinker Cope (1840-1897) was vertebrates—collecting that envisaged a a man of extraordinary brilliance and series of expeditions over a number of years ability; in fact, he was one of the greatest to predetermined localities. New horizons

20 were revealed to the world of science, and The beginnings of the modern period in assemblages of fossils were recovered that America may very well be dated by the literally astounded scholars throughout the entrance of the American Museum of Natu-

world. ral History into the field of active fossil Perhaps the rivalry between these two collecting and research. In 1891, Professor men stimulated each of them to efforts Henry Fairfield Osborn left Princeton much greater than they would have made University and came to New York to estab-

if all had been sweet and serene. However lish a new department of vertebrate

that may be, the fact is that the work of paleontology at the American Museum. Cope and Marsh, added to the earlier work Osborn, with his lifelong friend Professor of Leidy, formed the basis for modern William Berryman Scott, was a disciple of vertebrate paleontology in America, and Cope and had studied in Europe under in the world for that matter, because these Huxley and other famous teachers. With men established entirely new techniques of his arrival in New York, the American collecting, preparing, and studying fossils. Museum began a vigorous program of Men such as these have transformed verte- active work in the field of vertebrate fossils, brate paleontology from a comparatively a program in which the collecting, study, passive science, based upon the chance dis- and exhibition of dinosaurs played a large covery of isolated data, to a vigorous, active and important part.

branch of study which owes its modern One of Osborn's first acts was to gather

success to long-range co-ordinated plan- about him a staff of highly competent men: ning of world-wide scope. And in this field Dr. Jacob Wormian, one of Cope's as- of scholarly endeavor America has played sistants; Dr. William D. Matthew, a gifted a leading role, thanks in part to the solid paleontologist who will always stand as one foundations built by Leidy, Marsh, and of the leading figures in the annals of Cope. American paleontology; Dr. Walter What might be termed the modern Granger, a collector who has never been period in the exploration and study of dino- surpassed; Dr. Barnum Brown, who has

saurs and other fossil vertebrates had its devoted his life to the collecting and study-

beginnings in the last decade of the nine- ing of dinosaurs; Mr. Adam Hermann, who teenth century. At that time a generation of received his training in the preparation of younger men who had been students of fossils under Marsh; and under Hermann a Marsh or Cope came to the fore in this corps of skillful preparators and collectors, country, while in Europe the subject was notably Messrs. Albert Thomson, Charles being expounded to enthusiastic students Lang, and Otto Falkenbach. With a staff by such great authorities as Huxley in such as this the American Museum was England and von Zittel in Germany. Co- bound to make great strides in the entire incidentally there was a flowering of the field of vertebrate paleontology. larger Natural History museums in America Soon after Osborn's association with the and in the Old World, with the consequent American Museum, the institution was able opening of opportunities for fossil collecting to purchase, through the munificence of on an adequately planned and well- Morris Ketchum Jesup, the great collec- executed scale. tion of fossils amassed by Cope during the

21 a

years of his most active collecting trips— persistent efforts of Mr. Charles W. Gil- collection upon which Cope had spent his more, one of the great modern authorities entire personal fortune and the most pro- on the dinosaurs. ductive vears of his life. With this as a Early in the twentieth century Andrew foundation, the Museum's program in Carnegie became interested in dinosaurs, vertebrate paleontologv had an auspicious with the result that the Carnegie Museum start. in Pittsburgh embarked upon a period of Late in the 1890's a series of expeditions intensive dinosaur work. As a result a tre- for dinosaurs was inaugurated at a locality mendous quarry of Morrison age was ex- known as "Bone Cabin Quarry" in Wyo- cavated in eastern Utah, and a great ming. Here the great skeleton of Brotito- amount of material was taken to Pittsburgh saurus and many other fossils of Morrison for preparation, study, and display. At the age were recovered, and from that time on, same time the Field Museum of Chicago the American Museum has taken the lead in (now the Chicago Natural History Mu- the collecting of these great Mesozoic rep- seum) was exploring for dinosaurs, with tiles. It has been a story that has extended satisfactory results. over a period of some 50 years, much of it In more recent years the National Mu- under the supervision of Barnum Brown. seum of Canada, in Ottawa, and the Boyal Expeditions have ranged far and wide over Ontario Museum, in Toronto, have carried the western part of North America, in on extensive programs of dinosaur collect-

Wyoming and Colorado, in Arizona and ing, particularly in the fossil fields of Texas, in Montana and Alberta. Collections Alberta. Fine exhibits of dinosaurs may be have been made in the deserts of Mongolia seen in these museums. and South Africa. Exchanges have been Thus it may be seen that there has been made with museums throughout the world. in this country since the beginning of the

The result is that the American Museum present century a vigorous program of now has a collection and an exhibition of dinosaur collecting among some of the dinosaurs and of many other fossil reptiles larger museums, and the result is that in that is absolutely unsurpassed. no other country can such a variety and But during this period there were other number of dinosaurs be found on display. institutions that were making great strides Some mention should be made of the in the excavation, study, and exhibition of work on fossil reptiles other than dinosaurs. dinosaurs and other fossil reptiles. Many years ago, Cope made extensive col- There was, of course, the Peabody Mu- lections in the Permian beds of Texas, and seum of Yale University, where the fossils as a result of his studies he showed how gathered together by Marsh are housed. important the early reptiles of Permian age

Here was one of the first great assemblages are in drawing up a complete and satisfac- of dinosaurs, a collection that is still of tory picture of reptilian evolution. With the prime importance. There should be men- coming of the Cope collection to the tioned also the United States National Mu- American Museum, the foundations for an seum, an institution where work on dino- important Permian collection were estab- saurs has always been accorded much lished. In those early days of paleontology attention, due to the long-continued and many Permian and Triassic reptiles were

22 being discovered in South Africa, and were studied by Professor Ermine C. Case.

being described by Sir Richard Owen and What is to be the future of fossil collect-

other authorities at the British Museum. ing? Many years ago it was thought by Professor Osborn realized the importance certain scientists that when intensive col-

of having the South African fossil reptiles lections had been made, the fossil "lode"

represented in the American Museum, so would, so to speak, "peter out." But the

he instituted a policy of acquiring such more the fossil fields are worked the more

specimens. As a result the American Mu- they produce, and all the time new fossil seum possesses an important collection of fields are being found. Chinese paleontolo-

Permo-Triassic reptiles from the Karroo gists, in the midst of war and tribulations desert, collected for the most part by Dr. unequalled in human history, discovered a Robert Broom, a South African authority dinosaur skeleton in Yunnan Province in

on these ancient vertebrates. the year 1938, excavated it, brought it to More than a half-century ago one of Chungking, and published a descriptive Marsh's students, Professor Samuel Wen- monograph in 1942. Which goes to show dell Williston went from New Haven to that fossils will out, whether there be flood,

the University of Kansas. There he built fire, famine, pestilence, or war. up an unexcelled collection of aquatic The pattern for the future of fossil col-

reptiles from the Niobrara Cretaceous beds lecting has already been set. It will be a of Kansas, a work which so enhanced his future of co-operation among institutions. scientific reputation that he was called to The larger places with ambitious programs the University of Chicago as Professor of will make comprehensive collections in- Paleontology. cluding those of the large and expensive At Chicago he, with the able assistance dinosaurs. The smaller museums, including of Mr. Paul Miller, instituted a program of many university museums, will concentrate Permian work extending over many years, upon the very important but less showy so that the Walker Museum of Chicago Uni- Permo-Triassic reptiles. The museums will versity has one of the outstanding Permian work together, exchanging specimens and collections and exhibitions. data, so that in time representative displays Other American institutions have im- may be found in many places throughout portant fossil reptile collections, notably the the earth. One thing is sure, fossil collecting Museum of Comparative Zoology at Har- will go on as long as man remains a curious vard University, where much work has animal. And the search for dinosaurs, their been done on Permo-Triassic reptiles in contemporaries, and their forebears will be recent years under the able direction of carried to the most distant reaches of the

Professor Alfred S. Romer, the Museum of globe, to the Americas and Europe, to Asia

Paleontology of the University of Cali- and Africa and Australia. It is one field of fornia, with fine Triassic collections made collecting in which there is never any under the guidance of Professors danger of extinction of the supply, J. C. Mer- where riam and Charles L. Camp, and the Mu- wise and co-ordinated policies will furnish seum of the University of Michigan, in ample collections for everybody. which are to be found Permian and Triassic A list of museums in North America reptiles and amphibians collected and where fossil amphibians and reptiles may

23 be seen on display is presented below. The 8. Royal Ontario Museum, Toronto, listing is from east to west and not neces- Canada. sarily in order of importance. A notable display of dinosaurs from the upper Cretaceous beds of Alberta. 1. American Museum of Natural His- tory, New York. 9. Carnegie Museum, Pittsburgh, Pa. The fossil reptile exhibits in this museum consist The outstanding display of fossil reptiles in the for the most part of an extraordinary series of world is to be seen in this museum. The exhibits Jurassic dinosaurs, collected in the Morrison beds of are dominated by skeletons and skulls of dinosaurs, Utah. but there are also important displays of other fossil reptiles, notably pelyeosaurs, mammal-like reptiles, 10. Museum of Paleontology of the Uni- thecodonts, turtles, crocodilians, ichthyosaurs, plesi- osaurs, and flying reptiles. versity of Michigan, Ann Arbor, Mich.

A notable collection of Permian and Triassic am- 2. United States National Museum, phibians and reptiles from Texas and adjacent re- Washington, D.C. gions.

Here are found many notable displays of dinosaurs, 11. Chicago Natural History Museum, some of which were collected and studied by Pro- fessor Marsh. There are also exhibits of Permian Chicago, III. reptiles, turtles, and in addition some unusual At this museum may be seen some specimens of specimens of fossil lizards. dinosaurs.

3. Peabody University, Museum of Yale 12. Walker Museum of the University Haven, Conn. New of Chicago, Chicago, III.

The Peabody Museum collection is particularly Here, without doubt, is to be seen the finest dis- important for the wealth of dinosaurs that it con- play of North American Permian vertebrates in tains. A number of fine skeletons are on display. existence. There also are some important reptiles from the Karroo beds of South Africa. 4. Museum of Comparative Zoology of

Harvard University, Cambridge, Mass. 13. Dyche Museum of the University of The exhibits at this museum are noteworthy be- Kansas, Lawrence, Kans. cause of the Permian forms that are shown. There The fossil reptile collection in this institution is are also some important displays of aquatic reptiles. noted for the skeletons of the aquatic mosasaurs, 5. Academy of Natural Sciences, Phila- from the Niobrara Cretaceous beds of Kansas. delphia, Pa. 14. Colorado Museum of Natural His- Some fine ichthyosaurs specimens of and plesio- tory, Denver, Colo. saurs, collected in England about 100 years ago. in this Here also is the first dinosaur skeleton found in Several dinosaur skeletons are on display North America (Hadrosaurus).

6. Amherst College Museum, Amherst, 15. Museum of Paleontology of the Mass. University of California, Berkeley, Cal.

A mounted skeleton of the duck-billed dinosaur, The fossil reptiles are mainly those found in the Trachodon. Pacific coast and the southwestern regions of the United States. Here are seen Triassic reptiles from 7. National Museum of Canada, Ot- Arizona and Cretaceous forms from California. tawa. 16. California Institute of Technology, At this museum is housed a particularly fine Pasadena, Cal. exhibit of dinosaurs from the Cretaceous beds of western Canada. Reptiles from the Pacific coast region.

24 Hunting Dinosaurs

^^ NE OF THE QUESTIONS most fre- worked to a certain degree in a blind way, exploring ( J quentlv asked of the paleontologist because the territory they were | is, "How do you find these fossils?" was essentially a new region. And the same

Indeed, it is puzzling to the uninitiated how is true, although to a continually lesser the paleontologist will announce in the degree, at the present time whenever ex- spring that he is going out to hunt fossils peditions go into relatively unknown parts and then go to some distant region in the of the earth—as for example the Central summer and make good his promise. How Asiatic Expeditions of the American Mu- does one know where to look for the things? seum of Natural History to Mongolia. For

How does one go about it? Does one start many regions, however, the rocks of the by digging a hole in the ground, which earth have been studied and mapped in a mysteriously brings to light a new and fairly adequate manner, so that the strange variety of dinosaur? paleontologist goes to localities where he

There is nothing really mysterious about will be reasonably certain of finding fossils the process of hunting—and finding—dino- of the type in which he is interested. saurs, or other fossils for that matter. The The entire procedure is really a rather technique is mainly a combination of good interesting process of round robin reason- geological judgment, horse sense, persever- ing. Most of the sedimentary rocks of the ance, and hard work. earth's surface are dated by the fossils they

The first requisite for the dinosaur contain. Thus it is that in a new area, the hunter is to know where he should begin first clues to the age of the beds exposed to look for the fossils. The dinosaurs lived are obtained from fragmentary fossils, during the Mesozoic age of Earth History; found haphazardly and by chance during it necessarily follows that their remains will the course of general exploratory work. be found in rock strata of Mesozoic age, Having thus established the age of the and nowhere else. (By the same token, if beds exposed in the new region, and having one is looking for primitive fish, attention determined the extent of their exposures, is limited to early Paleozoic rocks, while if subsequent work is carried out in a sys- the search is concerned with the more ad- tematic way with definite ends in mind. vanced mammals, the regions explored are Perhaps a season of intensive search for those where Cenozoic rocks are exposed.) fossils fails to justify the hopes first enter-

Of course in the early days of fossil hunting tained by the enthusiastic bone hunter. If it was pretty much a hit-and-miss affair, so, the summer's work must be written off because the science of geology was so as "good experience," and fossil-avid eyes young that the rock layers of various ages are cast in other directions. But the were not well known nor were they ade- paleontologist of good judgment will rarely quately mapped. embark upon a program of intensive work

The early expeditions of the Territorial unless he is pretty sure that the results will Surveys and those of Cope and Marsh justify the expenditure of the time and

25 money that are allotted to him; consequent- the other busy searching for the next place

ly the results obtained by most fossil ex- to step. Which latter is more important

peditions are fairly consistently satisfactory. than it may sound at first, for much of the

Having picked a region for exploratory business of "walking out" a formation in-

work, the fossil hunter follows a definite volves a constant scramble along cliff faces, and systematic procedure for ferreting out up and down the sides of canyons, in and

the dinosaurs, or fishes, or phytosaurs, or out of arroyos or washes.

mammals, or whatever he may be after. Of course it is important for the fossil

First, by a method of trial and error, he hunter to know just what he is looking for— learns just which levels or "horizons" in the indeed, much of the secret of successful

rock layers are the fossil-bearing ones. collecting is the recognition of a fossil as

Then he "walks out" the level, with one eye it is exposed in the strata, usually with

peeled for the precious fossils he is seeking, merely a trace of the entire organism show-

Fossils are of many kinds

Sometimes only an imprint of the skin is preserved. Here the skin itself has been replaced by minerals. (From a Duck-billed Dinosaur) skin

m

zm: Here the form of the animal is retained as well as the skeleton: a fine body example of the preservation of soft parts. (An ichthyosaur) outline

A.M.N.H. photographs

Beneath the skin, a coat of mail protected this bony armor animal and was fossilized. (A nodosaur)

17 bone A typical example of the parts usually found fossilized: portions of the skeleton of a small dinosaur from Mongolia

A.M.N.H. photographs

e One of the rarest fossils: a dino- zz saur egg over 60 million years old, compared with a hen's egg (left) and an alligator egg (right)

28 Fairly common are tracks made by dino- footprint saurs in mud and later changed to stone. This one held eighteen gallons of water

Photograph by courtesy of Roland T. Bird

- ing. And that brings us to the question of recent age, in which there has not been

"What is a fossil?" time for fossilization or "petrification." Al-

A fossil is the remains or the indication though the remains are not mineralized, of past life upon the earth. Originally the they are nonetheless fossils, because they word fossil, derived from the Latin fossilis represent the remnants of something that (dug up) applied to anything dug out of was once alive on the earth. the earth, whether it were the remains of Some fossils are found as molds or casts. animal or vegetable life, or minerals. In In these instances, the original organism modern usage, the term fossil is restricted has decayed or dissolved, leaving a hollow to the remains or indications of organisms impression in the sediment or the rock in which once lived on the earth. which it was entombed. The hollow impres-

Fossils are preserved in a variety of ways. sion is a mold. If that mold becomes filled Usually fossils are replacements in stone of with sand or mud, which eventually solidi- materials which were originally organic. fies to form stone, a cast is produced, a

A living animal, a sea-shell, a fish, a dino- fossil which preserves the external form but saur, a mammal, died and its body was not the internal microscopic structure of covered by the ooze of the ocean bottom, the original. by the mud of a shallow river, or by the In some cases even the soft parts are shifting sands of a desert. Thus entombed, fossilized, although this is unusual. When decay of the organic materials oftentimes we find a fossil of this type we can be sure was retarded, especially as regards the hard that conditions were such that the soft parts parts, such as shell or bones. Consequently were protected in some fashion against im- the breaking down of these hard portions mediate decay, while mineralization was of the organism was a slow process. And comparatively rapid. On page 26 the fos- if conditions were just right, it was accom- silized skin of a Duck-billed Dinosaur is panied by another process, namely the re- pictured. placement of the original material by Sometimes fossils are formed by unusual mineral matter, deposited by the waters minerals, such as iron pyrites, or opal. that percolated through the sediments in Many fossils are not the remains of the which the animal was buried. This replace- animals or plants, but merely the indica- ment was complete and molecular in nature, tions of such organic structures. Fossilized so that not only the external shape of the tracks are fairly common. Often fossilized shell or the bone was preserved in rock, but burrows are found, or fossilized insect nests. also the internal microscopic structure. So Even the marks made by leaves brushing it is that we are able to study a thoroughly across the mud are sometimes preserved as mineralized fossil shell or bone just as com- fossils. pletely as if we had the original shell or So it is that fossils may assume a variety bone to look at. of forms, and the fossil-hunter must be able

Such is the form of many fossils, but not to recognize fossils of these several types by any means all. For instance, some fossils in the field, and interpret them properly. are actually the original shells and bones, That is why he keeps one eye peeled as he with little or no mineral replacement. This scrambles along the face of a verv hard is often the case with fossils of a relatively and high cliff, under a very hot sun, barking

30 «^- Bad lands are good lands for fossil hunters. But rough cliffs like this one in Utah have scraped the shins of many a prospector who thought he saw some- thing just a little higher

A.M.N.H. photograph

•^^i Once discovered, the ancient bones are uncov- ered by careful work with pick, awl, and brush. During this delicate operation, the fossil hunter must often en- dure scorching sun, sand- storms, and sudden showers

Photograph by Barnum Brown

f^^- From inaccessible loca- tions fossilized bones weigh- ing several hundred pounds can be taken to the wagon road only with difficulty. Careful engineering is nec- essary to ensure their safe transportation

^» Finally the prehistoric treasure is hurried on its way to the railroad platform and

the museum, where it will be scientifically studied his shins, tearing his trousers, and sun- volves a careful uncovering of the bone burning his back. with pick, hammer, awl, and brush, so that Sooner or later he will find the traces of the extent of the skeleton may be judged. a fossil—perhaps some broken bits of bone Usually when this work is being done the or teeth, if he is out for dinosaurs. Then he sun is uncommonly hot and the air still and looks around to see if he can locate the stifling. Or it is windy enough to blow the place that is producing these broken bits— harassed fossil hunter "into the next the place where the more complete animal county," and at every move he gets his eyes is buried. Usually he has little success, the and mouth full of sand. Or there are a series broken bits were merely broken bits, the of sudden desert rain storms that necessi- fragments of an isolated bone or tooth. tate a series of frantic efforts to get the (Skeletons have a disconcerting trait of precious specimen covered by a canvas getting thoroughly dismembered and scat- tarpaulin before it gets wet. Or there are tered before they are ever fossilized.) But flies and hornets. every now and then the fragments lead to At any rate, the work must be done, and something bigger—above his head 20 feet done carefully. Every bone or tooth that is up on the side of the cliff some bones are exposed must be shellacked and covered protruding from the face of the rock. with tissue paper, otherwise it is apt to

Then comes the process of clambering up crumble to powder. Then the skeleton is to the fossil and establishing a place to removed, bone by bone, or else in blocks work, oftentimes with many a prayer for each containing several bones. To do this

"sky hooks" to help the struggling bone it is necessary to cover the part being re- hunter defy the law of gravity. After that moved with strips of burlap dipped in there is the tedious business of removing liquid plaster or in flour paste. When the the "overburden," the tons and tons of rock burlap and plaster or paste covering has that are usually piled on top of the fossil dried and hardened, it forms a strong cast and must be gotten out of the way. That over the bone or the series of bones, and is one of the great gambles in fossil hunt- thus prevents the fossil from breaking when ing. Sometimes considerable effort will be it is moved. In other words, the fossil is expended in removing the overburden, only "immobilized," in the same manner that a to find that the fossil "peters out" six feet broken arm or leg is immobilized bv a doc- in from the face of the cliff. But at other tor. Then, when the top and sides of the times the dreary work of picking, shoveling, specimen have been so secured, it is care- hauling, and often blasting, will be re- fully freed from the rock on which it is rest- warded by the exposure of a fine skeleton, ing, turned over, and the bottom is encased or even a whole series of skeletons. Some- in the plaster and burlap bandage or cinch. times fossils are found out on open flats, If the specimen is very large, sticks of wood, with little or no overburden. The fossil- or splints, are attached to the bandaged hunter then offers fervent thanks to a fossil to keep it from breaking of its own benign providence for giving him (at least weight. for one time) all gravy. Next the fossil has to be moved to a Then comes the work of exposing the suitable place and packed in a wooden fossil so that it can be removed. This in- box, in straw. Then the box is hauled to the

32 ^ In the museum lab- oratory, the shellacked wrappings and the excess rock are removed from the fossil. This requires skill, patience, and great delicacy of touch

A.M.N.H. photographs

y Illustrations of the fossil for publication in- clude not only photo- graphs but careful draw- ings made by scientific artists nearest railroad shipping point, and the museum the entire process that was gone specimen begins its trip to the museum. through in getting the specimen out of the

When one is hunting dinosaurs, which rock has to be reversed. First the fossil must are usually found in the most out-of-the- be unpacked. Then the burlap and plaster way places possible, and which often have cinches must be removed. After that there single bones weighing two or three hun- comes the long process of "preparing" it for dred pounds, the difficult nature of the study or exhibition. The bone must be freed work of fossil-hunting becomes painfully completely from its rock matrix, a pro- apparent. But in spite of the hard and hot cedure that requires skill, patience, and a work, the sand and the flies, the bad water, great delicacy of touch. Indeed, the process and the many natural discomforts that flesh of preparation is usually the longest and is heir to, the fossil-hunters love it. Take a most tedious part of paleontological tech- paleontologist's field trips away from him nology. As the rock is chipped away from and he is apt to get savage, or at least to the bone, the fossil is hardened with shellac. acquire a rather sour outlook upon life. Large bones are drilled, and steel rods are

Collecting the fossil and sending it to the inserted into them to support their dead museum is only part of the story. In the weight. Missing parts are filled in with

plaster. Thus it may be seen that the

preparation of a fossil skeleton is a long job, and when the work involves some-

thing as large as a big dinosaur, the task is truly colossal, requiring the full-time efforts of several skilled men for many months, or

even years. That is why only the large institutions are able to go after the big game of dinosaurs.

After the fossil is fully prepared, the

paleontologist at last begins his examina-

tion of it. The fossil must be compared with

other fossils, and identified. Perhaps it is

new. Then it must be carefully studied and a description written for publication in a

technical journal. For it is only through publication that a fossil collection has any real value. Unless the information gained

from the collecting and preparing of fossils

is made available through the printed page,

the assemblage of specimens is essentially a pile of meaningless junk. The reputation of a scientist and of the institution for which he works depends largely upon his publications. Without a solid foundation of

scientific publications emanating from its

•^^ If the extinct animal is to be placed on

exhibition, the skeleton is mounted in posi- tion. The bones may have been greatly dis- arranged when found; here they are accurately assembled and held in a natural posture by concealed supports that will be scarcely visible

when the scaffolding is removed

A.M.N.H. photograph activities, a paleontological museum is not museum visitor how the dinosaur or the a museum but merely a warehouse or a phytosaur or the pterosaur looked in life. showplace. Thus the publication of the So, that long-suffering and patient being, studies made on the fossils is one of the the artist, is called in again, this time to most important functions of the museum. project himself in his mind's eye back to a The scientist studies the material and pre- distant age, to make a portrait of a beast pares a manuscript. A trained scientific long since gone from the face of the earth. artist working with him makes drawings of He works with the paleontologist on this. the fossils to illustrate the publication. To- Together they compare the fossil with the gether they produce the scientific paper nearest related animal extinct or living. which makes the information on the fossil Together they figuratively hang muscles on available to students all over the world, the bones and then stretch a skin over the and gives to it its true value. muscles and then brush a color over the

If the specimen is sufficiently well pre- skin. At last the animal stands as he may served, and of sufficient importance, it will have appeared in life, and in all fairness it be placed in the exhibition hall. Only the must be said that there is every reason to more choice fossils, however, are placed on believe that a careful restoration made by public exhibit; the bulk of the collection is a competent artist, working with a com- retained in storage for study and future petent paleontologist who knows his reference. This is modern museum practice, anatomy, is pretty close to the truth. There for we now believe that exhibits should tell remains only the task for the artist of a story by well chosen examples, rather putting in some contemporaneous scenery than serve as dismal arrays of specimens on and vegetation (and that is no mean job), shelves, which was the philosophy of mu- and the restoration is ready to go on exhibi- seum display a half-century or so ago. tion along with the fossil, or in a book such

If the specimen to be exhibited is a skele- as this. ton, it must be properly assembled, and this But is that all? Not quite, for the labels again is a job requiring a great deal of must be written. One explanation of a good skill and considerable time. Irons must be museum exhibit is that it consists of a series bent to support the bones, and fastened of excellent labels illustrated by good speci- together to make a sort of frame upon mens. Well, the labels are prepared, and which the skeleton is hung. The preparator then the exhibit is ready, at long last. and the scientist work together on this, and It has been a long story, from the fossil in oftentimes the job requires a great deal of the field to the exhibit in the hall, a story supplementary study in order that the pose involving the expenditure of many man- will be anatomically correct and at the same hours of time by various trained persons.

time interesting. But they keep at it in the But in the end the results are worth the museum laboratory, and after weeks or price, for we have learned more about the months of work the specimen finally stands past history of the earth and the proper articulated, a thing of real structural interpretation of our modern world depends

beauty, ready for the exhibition hall. greatly upon our knowledge of its past. But the end may not yet be in sight. For Some of the more important localities at the paleontologist may decide that a which fossil amphibians and reptiles have

painted restoration is needed, to show the been found are discussed in Chapter 17.

35 The Age of Reptiles

e are living in the Age of Man, a half-million to a million years, which Wi the period in which man rules the seems like a long time. Of that great period, J earth. For better or for worse we man has written the last seven thousand are supreme over all other forms of life. years of it into his record; before the period

No longer is our existence threatened by of recorded history man was a primitive large animals, as was the case with some savage, wresting his living from the soil and of our not very distant forebears. No longer from the chase, ever surrounded by large are we so seriously threatened by the less beasts that challenged his right to the fields spectacular but much more deadly micro- and forests. scopic parasites, as were our ancestors of a The dinosaurs lived for a period of about few hundreds of years ago. There is nothing 140 million years, during which time they to challenge the supremacy of man upon were the dominant animals of the earth. the earth, except man himself. For a period at least 140 times as long as

It is readily understandable that having the entire history of man, these ancient achieved this supremacy, we are apt to animals lived and fought and died—the think of ourselves as the culmination of lords of creation. Who are we to say that evolutionary history. And from our present- they were not successful? day standpoint this is true. No animal in Perhaps you are wondering about the the history of the earth has risen to the rather casual bandying about of time supreme dominance over the lands and the figures so astronomical as these. What waters that is ours. Therefore, we can say right have we to say that the dinosaurs that no animal, to our way of thinking, lived so many millions of years ago, or that has been so successful as we are. they persisted for so many millions of

Yet there is another way of looking at years? this matter. Let us forget our natural bias This brings us to the subject of geologic as human beings and regard the question time. from an objective viewpoint. The immensity of geologic time is so

Many ages ago, in the dim past of Earth great that it is difficult for the human mind

History, lived the dinosaurs. These animals to grasp readily the reality of its extent. arose, evolved, and became extinct at ages It is almost as if one were to try to under- so far distant from us that we can hardly stand infinity. stretch the imagination sufficiently to com- The earth is about two billion years old. prehend the immense passage of time that This is not a mere guess but is the result of separates them from us. Since they are careful, cumulative studies by many investi- gone from the face of the earth, we are gators working over a long period of years inclined to regard them as "failures" in the and along various lines of evidence. Of long history of life. Were they really particular use are the investigations of failures? radioactive materials in rocks of ancient

Man has lived on this earth for perhaps age—indeed, it is by the study of the slow

36 disintegration of radium and uranium into there was a time lapse of some 59 million lead that we have extended our conception years between the disappearance of the

of geologic time to its present tremendous last dinosaurs and the appearance of man,

limits. as revealed by the science of paleontology. Of the two billion years of Earth History, The 60 million years during which the only about one-fourth, or 500 million years warm-blooded mammals attained their

of it contain adequate fossil records. In supremacy may seem like an immensely

other words, 500 million years ago life on long stretch of time, yet it was less than the earth had reached a stage so that the half as long as the reign of the dinosaurs remains of plants and animals were of suf- on earth.

ficient density and complexity as to be pre- Carrying the story still further into the

served in the form of fossils. In this 500- distant mists of geological antiquity, it may million-year fossil record we find the be seen that the age of dinosaurs, tremen- dinosaurs appearing some 200 million years dously vast to our way of thinking, occu- ago and persisting through a period of pied but a fraction of the time since the

about 140 million years' duration, to be- first well-preserved fossils appeared in the come extinct about 60 million years ago. geologic history of the world.

Perhaps these are mere figures. Let us Finally, the period of fossil history is but look at the record in another way. one-fourth of the period of Earth History, The recorded history of man goes back as was mentioned above. about seven thousand years, to about the Just as our own written history may be time of 5000 B.C. Within this stretch of subdivided into stated periods, marked by time are encompassed the events of history, certain events or by certain series of events,

as we know them, from the rise of the early so is geologic history divided by the se- civilizations of the Middle East to the quence of events of Earth History. present stage of our modern machine age. The Mesozoic era was primarily the age The days of ancient Egypt seem vaguely of dinosaurs. Of course there were other distant to us, yet as compared to the entire types of animals living at that time; fishes history of man on the earth they are as but and aquatic reptiles in the water, flying

yesterday, for man first appeared about one reptiles and primitive birds in the air, and million years ago. The 7000 years of history small, archaic warm-blooded mammals on seem indeed of rather insignificant propor- the land. But these animals, important tions when compared with the one million as some of them might be in view of the

years of prehistory as revealed by the subsequent history of animal life, played science of archaeology. for the most part relatively insignificant Man, even in his most primitive mani- roles in the great drama of Earth History

festations, is a relatively late product of during Mesozoic times. The real actors on evolutionary history, as compared with this stage were the dinosaurs.

most of the life on this earth. Comic strips The Mesozoic is often known as the "Age and jokes to the contrary, the dinosaurs had of Reptiles," since dinosaurs are reptiles and been gone and forgotten for a great many were dominant at that time. This, however, million years before man ever made his first may not carry quite a true picture of things appearance in a troubled world. In fact, as they were, for as may be seen by the

37 DINOSAURS are extremely old when com- pared with the earliest human remains. But they are relatively late in the 2-billion-year history of the earth A.M.N.H. photograph

7 Age of Man 1 million years

Dinosaurs extinct. Dinosaurs appeared about First mammals appeared 200 million years ago w_ about 60 million years ago

First reptiles appeared about 245 million years ago SiNOSAURS

First land vertebrates Oldest fossils (Amphibians are about appeared 500 million about years old 340 million

\

Origin of earth m 2 billion years ago if 3 inches = Age of Man

(1 million years)

fik

N 1 /50 inch = entire period

of recorded history

(5000 B.C. to present)

accompanying figure, the reptiles appeared was the period during which the first land on the earth approximately 245 million vertebrates were evolving from their fish years ago (Late Paleozoic era), and were ancestors. It was the period during which even then dominant on the land. So the the basic patterns for reptilian evolution "Age of Reptiles" might be thought of as began to be established. extending at least from the beginning of These, the Age of Amphibians and the the Permian period (about 225 million years Age of Reptiles are the periods of Earth ago), at which time the primitive reptiles History with which we shall be especially had become well-established upon the concerned in the following pages of this earth, to the end of the Mesozoic era, when book. We are interested particularly in the reptilian dominance ceased with the disap- dinosaurs, but in order to understand them

pearance of the last dinosaurs. properly it will be necessary to give some Preceding this Age of Reptiles was an attention to their predecessors and their

Age of Amphibians, including in a general contemporaries. So it is that our story be- way what the geologist refers to as Mis- gins with the emergence of the vertebrates sissippian and Pennsylvanian times. This from their watery ancestral home.

39 DOMINANT ANIMAL LIFI The First Land Animals

I e do not know when life began the Devonian period (340-275 million years

\A/ on the earth, and it seems likely ago), they were abundant and dominant in that the answer to this question the waters of the earth. There were many will remain forever hidden from us. What kinds of Devonian fishes, some large, some

we do know is that it was some 500 million small, some fast-swimming and predaceous years ago when the plants and animals of hunters, others flattened burrowers and early geologic history had reached a stage of grovelers in the muds of shallow bottoms. development where they produced hard Among the Devonian fishes there were cer- parts capable of being preserved as fossils. tain ones, belonging to a group known as At that distant date there seemingly was the crossopterygian (cross-op-ter-ij-e-yan)

no land life; all life was in the sea. More- or lobe-finned fishes, which were destined over, there were no vertebrates, or back- to play a very important role in the history boned animals, living—at least none of suf- of evolution, for these were the immediate,

ficient complexity that they left hard struc- direct ancestors of the first land-living

tures to be preserved in the form of fossils. vertebrates. According to the fossil record, the animals The lobe-finned or crossopterygian fishes of that time were mostly various types of were of medium size and were covered by

sea-shells and crablike forms. It is probable, a heavy armor of scales. Some of the signifi- however, that even by the beginnings of cant structures characterizing these early

Cambrian times, about 540 million years fish were:

ago, the basic patterns for the backboned a.

animals had been established, for it was The arrangement of the bones in the skull

at an early stage in the Paleozoic era that according to a pattern that is comparable,

the first vertebrates appeared. These were bone by bone, with the skull pattern of the primitive, fishlike forms. early land-living vertebrates,

The fishes rose and evolved at a rapid b. rate, so that by middle Paleozoic times, in The microscopic structure of the teeth,

Into a world of primitive backboned ani- finned group represented above by Os- mals came many kinds of fishes in the period teolepis were to become the direct ancestors between 275 and 340 million years ago. of the first backboned animals to live on Among these, the crossopterygian or lobe- land

41 ^i Only during the last 500 million years have plants nd animals produced hard parts capable of being fossil- Drawings by John C. Germann zed. Here is a simplified chart of that quarter of the arth's history which is virtually identical with the struc- mic undulations of the body, passing to the ture of the teeth in the early land-living tail and acting against the dense water in vertebrates. which it lives. The fins are used mainly as c. balancing organs. In the land animals the The presence of internal nares—the inner paired limbs, derived from the fish fins, be- openings of the nose—a character found in come the propelling mechanisms, while the land-living, air-breathing animals, tail, in part the propelling structure of the d. fish, becomes a balancing member, The arrangement of the bones in the fins e.

in a manner that is comparable with the Finally, the fish lays its eggs in the water, arrangement of the bones in the limbs of by which medium they are kept moist and the early land-living vertebrates. able to function for the purpose of hatching

a new generation of fishes. In the land- The transition in the vertebrates from an living vertebrates there must either be a aquatic to a terrestrial or land-living mode return to the water to deposit the eggs, or

of life was one of the great forward steps new methods must be developed for pre-

in evolutionary history. Indeed, it was a venting desiccation and destruction of the

step of such magnitude that it might be new generation during its embrvonic life. considered as an important revolution in the

history of life on the earth. The transition among vertebrates from

Consider the facts, life in the water to life on land took place in

a. Upper Devonian times, about 300 million

The fish lives in a dense medium, which years ago. Certain crossopterygian fishes

buoys it up. Therefore to the fish gravity is struggled out onto the land and the first land-

a problem of little consequence. But to the living amphibians came into being. land-living animal gravity becomes a prob- The amphibians are those cold-blooded lem of the greatest consequence, because land animals which typically return to the

the body must support itself against a con- water to lay their eggs. The young are stant downward pull. hatched as fishlike tadpoles and go through

b. a water-living, gill-breathing stage, after

The fish is prevented from drying up by the which they come out onto the land to live

life-long bath to which it is subjected. In as air-breathing adults. We know them to-

the air, on the other hand, there is constant day as the salamanders, the toads and frogs, evaporation, so that in the land-living ani- and certain legless tropical forms, the mal provision must be made against the Gymnophiona, Coecilia, or Apoda (jim-no- drying up of the fluids within the body, fee-o-na) (see-siL-ee-ya) (a-POAD-a).

c. The amphibians as we know them are the

The fish extracts oxygen from the water by meek descendants of a long line, living means of gills. The land vertebrate develops their harmless lives in the shelter of the in the lung a new means of obtaining grassy banks that line our streams and oxygen from the air. ponds, or unobtrusively hunting insects in d. the leafy shadows of the garden or wood- The fish moves largely by means of rhyth- land. However, for a geologically brief

42 .

period of time—that time when the verte- which is rather interesting, may be outlined

brates were first invading the land—the briefly as follows. amphibians enjoyed a period of terrestrial These amphibians began their evolution-

dominance, a period when they were the ary life in Mississippian and Pennsylvanian masters of the solid earth. times as predominantly water-living forms,

This dominance had its beginnings in the having relatively weak limbs. These early

first venturings of vertebrates from an labyrinthodonts are known as the Embol-

aquatic to a terrestrial mode of life, when omeri (em-bol-o-mer-ee). From the Em- there was nothing to dispute the claims of bolomeri there evolved large, robust, the primitive amphibians to the firm ground land-living types with strong legs, the

as a new environment. It had its beginnings Rhachitomi (rak-iT-o-me). The Rhachitomi, with certain Upper Devonian forms such living in the Permian period, were among as Ichthijostega (ik-thee-o-STEEG-a), an early the largest and most powerful of the

amphibian from Greenland that shows in terrestrial vertebrates, and at first glance it

its structure the heritage of its crossop- would look as if they were admirably suited terygian ancestors. to establish a successful line of aggressive The development of the Amphibia land-living animals. Such, however, was not

reached its culmination in a line of late the case, for in Triassic times the evolution Paleozoic and early Mesozoic forms known of the labyrinthodonts turned backward, so as labyrinthodonts (lab-i-RiNTH-o-donts), so to speak, and these animals returned to a named from the labyrinth-like internal water-living mode of existence. These structure of their teeth—a direct inheritance Triassic forms are known as the Stereo-

from their crossopterygian fish ancestors. spondyli (ster-ee-o-SPON-dil-ee), and they The labyrinthodont amphibians appeared were the last of the labyrinthodonts. At the in Mississippian times, seemingly as direct end of the Triassic they became extinct, and descendants from the ichthyostegids (see thus ended the bid of the amphibians for a Ichthijostega, above), and they persisted position of dominance or partial dominance through the Permian period, finally to be- among the land-living animals. come extinct in the Triassic some 170 Perhaps the evolution of these amphibi-

million years ago. During this time they de- ans may be made clearer by outlining it as veloped so that some of them became rather shown below. large, the giants of their kind. One of the best known and very charac- The evolution of the labyrinthodonts, teristic labyrinthodonts was Eryops (ER-ee-

Evolution of the Labyrinthodontia

Triassic From 200 to 155 million years ago

lull deep — Skull very flat

* mp Backbone .imp.. '* EMBOLOMERI •ackban. complex, RHACHITOMI*- STEREOS PONDYLI vertebrae interlocking

ibi i weak — — — — — — llmbi strong — — .— — — • — Llmbf weak CREATURES THAT LEFT THE WATER: The rise and decline of the labyrinthodont amphibians. The primitive labyrinthodonts, such as the Pennsylvanian form, Diplorerte- bron, were long-bodied and rather weak- limbed animals, not so very far removed from their fish ancestors. The peak of labyrintho- dont evolution was reached in large, robust, rather aggressive Permian types, such as Eryops. Finally in Triassic times these verte- brates returned to the water from which their ancestors had emerged, so that the head and body became flat and the limbs were reduced in size and strength, as in Buettneria

Restorations by John C. Germann

Diplovertebron ops). This large amphibian is found in the haps one of the most interesting of the Permian beds of Texas, and as may be seen, non-labyrinthodont forms was Diplocaulus it was a strong, heavy, land-living animal. (dip-lo-KAWL-us), belonging to a group Here was the high point in amphibian known as the Nectridia. This was a peculi- evolution. Look at Eryops and you see the arly flat, wide, water-living amphibian with culmination of development in the Am- an extraordinarily bizarre skull, shaped phibia, an animal that was a truly dominant somewhat like a tremendously broad arrow- element in his environment. All that went head. before was building up to this climax in The ancestry of our modern amphibians, amphibian history, all that has come since though obscured in the mists of geologic is in a sense an anticlimax. time, is probably dual in pattern. There is There were various amphibians con- indication that the frogs and toads are de- temporaneous with Eryops. Some of them scended from a labyrinthodont stem, while were small, active labyrinthodonts. Others the salamanders and perhaps the coecilians were not labyrinthodonts at all, for at that are derived from certain small, salamander- time there were several lines of amphibian like amphibians of Pennsylvanian age known development evolving side by side. Per- as lepospondyls (lep-o-spoN-dils).

44 The frogs and toads have become highly The salamanders are seemingly rather modified. The head is large, the neck and primitive amphibians that have returned to body short. The elongated hind legs serve a life spent largely in the water or in moist as efficient springs to propel the animal in places. Consequently they show a certain long leaps, while the short forelegs are amount of "regressive evolution," such as firmly attached to the body and strength- the secondary development of cartilage in ened, to take up the shock of landing. The parts of the skeleton that once were com- tail, so typical of most vertebrates, has been pletely bony. Some of the Pennsylvanian lost. All in all these melodious friends of the lepospondyls seem to indicate an ancestry swamp and stream are highly successful for the salamanders. animals. They had their beginnings in It is possible that the Gymnophiona or Triassic times, and from the Jurassic to the coecilians also were derived from a Recent period they have persisted in es- lepospondyl ancestry, but since no fossils sentially their present highly modified are known, the history of these small, leg- condition. less, tropical amphibians must remain largely a matter of conjecture.

An extraordinary skull shaped somewhat like a broad arrowhead distinguished the early amphibian known as Diplocaulus Restoration by John C. Germann EVOLUTION OF THE AMPHIBIA. The pres- ent-day frogs and toads apparently descended from one stem; the salamanders (and perhaps the coe- cilians) from another

Restorations by John C. Germann

46 Primitive Reptiles

e have seen how the amphibians duction. The reptiles prevailed because in \A/ arose, reached the culmination of them a new method of perpetuating the their evolutionary development and species had evolved. It is probable that the for a geologically brief period enjoyed labyrinthodont amphibians had to return to a certain degree of dominance among the the water for the laying of the eggs, just as animals living on the land. We have seen is the case with most of the amphibians of how this culmination and dominance of the the present day. In the early reptiles, how- amphibians was attained by the late Paleo- ever, it is probable that the specialized zoic labyrinthodonts, the giants, and in amniote egg had been perfected. Indeed, many ways the most highly evolved of these the appearance of the amniote egg was one primitive land vertebrates. of the great forward steps in vertebrate The labyrinthodonts, in spite of their evolution, for with the development of this evolutionary progress, were unable to new type of reproduction the vertebrate evolve to any great eminence because at an was henceforth freed from its bondage to early stage in their history they suffered the water. from the competition of other land verte- The amniote egg is, briefly, the encased brates that were better adapted to a egg of reptiles and birds; the egg in which terrestrial environment than they were. the developing embryo is protected by an These were the reptiles, the cold-blooded enveloping sac, the amnion, while the entire land animals in which the young develops egg is generally enclosed in a hard, protec- directly without any tadpole stage. tive shell. The reptiles arose soon after the appear- ance of the labyrinthodonts and developed side by side with them. By Permian times there was actually a certain amount of "pushing and shoving" between the reptiles and the amphibians for elbow room upon the surface of the land. But the amphibians lost the battle; the last of the labyrintho- donts retreated once again to the primitive home for all life, the water, there to enjoy a brief respite of existence before they finally became extinct, while the reptiles, The protected egg which presumably gave the early reptiles their initial advantage over the ever evolving and increasing, reached hith- amphibians. Here for the first time the de- erto unsealed heights in the climb up the veloping embryo is freed from its prior bond- evolutionary ladder. age to the water, by means of a hard, protec- Why did the amphibians lose the evolu- tive shell and an enveloping sac (the amnion) tionary race to the reptiles? The answer —hence the name, amniote egg From Romer's Alan and the Vertebrates, is probably to be found in one word, repro- The University of Chicago Press 47J It was probably the development of this potentialities. They were free of the water. egg that marked the first divergence of the They could venture over the face of the early reptiles from the amphibians, for just earth and continue their kind in regions as certain fish were the progenitors of the where the less efficient amphibians could amphibians, so were certain amphibians the not survive. Thus was born a mighty race. progenitors of the reptiles. And the basic The earliest reptiles were very much like reptilian grandparents were labyrintho- their amphibian ancestors. In fact, some of donts. Therefore, while the thesis of laby- the most primitive reptiles were so very am- rinthodont extinction before the onslaught phibian-like that there has been a great deal of their reptilian competitors is valid, it is of argument as to whether these basic rep- in a way equally valid to say that one tiles might not more properly be regarded branch of the labyrinthodont line was con- as advanced amphibians. So it goes. The tinued by the reptiles because certain early more we know about the classification of labyrinthodonts were transformed into animals, the less distinct become the lines reptiles. of demarcation separating one form from

The first reptiles had great evolutionary another or one group from another. In other words, we find the intermediate stages which prove the validity of evolution. The "grandfather" of the reptiles: Sey- Certainly there could hardly be an ani- mouria. This animal formed an almost per- mal more exactly intermediate in its fect intermediate link between the early am- anatomical features between the amphibi- phibians and the ensuing reptiles, and repre- sents the structural ancestral type from which ans and the reptiles than the Permian all the reptiles evolved genus, Seymouria (see-MOOR-e-ya), from Restoration by F. L. Jaques the rocks known as the red beds of Texas. This animal approximates structurally the

stem for all reptilian life; it is the "grand-

father reptile." The reptiles may be classified in a broad, general way on the basis of skull design, as follows:

a. Anapsida (an-APS-i-da)

Skull roof solid, without any openings be- hind the eye.

b. Synapsida (sine-APS-i-da) Skull roof perforated by a lower opening behind the eye bounded above by the postorbital and squamosal bones,

c. Parapsida (par-APS-i-da) Skull roof perforated by an upper opening behind the eye, bounded below by the post-

48 frontal and supratemporal bones.

d. Diapsida (dye-APS-i-da) Euryapsida 1 (your-e-APS-i-da) Skull roof perforated by a lower and an Skull roof perforated by an upper opening upper opening behind the eye, these open- behind the eye, bounded below by the ings separated by the postorbital and postorbital and squamosal bones. squamosal bones.

1 1 am indebted to Professor A. S. Romer of The first reptiles were anapsids. They Harvard University for the suggestion as to the derivation and the use of this name. were the reptiles with solidly roofed skulls,

THE FIVE BASIC TYPES of reptilian skulls. The anapsid skull had no openings behind the eye. The synapsid skull had a temporal opening behind the eye, below the squamosal and postorbital bones. The parapsid skull had a temporal opening behind the eye but above the supratemporal and postfrontal bones. The euryapsid skull had one above the squamosal and postorbital bones. The diapsid skull had two temporal openings behind the eye, separated by the squamosal and postorbital bones

Drawings by John C. Germann

.NAPSID squamosal postorbi squamosal postorbital

EURYAPSID father reptile," Seijmouria. These are often known as the seymouriamorphs. Then there was a line of small Permian cotylosaurs, showing certain specializations, known as the labidosaurs (LAB-i-do-sawrs) or capto- rhinomorphs (kap-to-RiNE-o-morfs). Fi- nally, the third group of cotylosaurs, known as the diadectomorphs (dye-a-DEKT-o- morfs), consisted of quite large reptiles living in the Permian period, and small, highly specialized survivors persisting through the Triassic period. Labidosaurus was small, like Seymouria. It had the long body and the sprawling, weak limbs of the primitive reptile. The

skull, as in all anapsids, was roofed over by solid bone, and was abruptly truncated be- hind. A characteristic feature of this animal was the overhung, or hooked upper jaw. Diadectes (dye-a-DEKT-eez) was a rather

large Permian reptile, some five or six feet in length. The legs were sprawling, as in From "grandfather" Seytnouria, two general the other primitive anapsids, so that this lines of reptiles descended. In one, the ani- animal must have been rather clumsy when mals remained small, like Labidosaurus. In the other, there was a tendency to giantism, walking. Diadectes seemingly was a plant- as may be seen in Diadectes from North eating reptile, for the teeth were blunt and

America and in the large pariasaurs from the peglike, and not at all suited to catching Old World, one of which is shown opposite animals as were the pointed, spikelike teeth Restorations by John C. Germann of Seijmouria and Labidosaurus. A remark- able feature of Diadectes was the large

an inheritance from the solid, bony skulls of pineal opening on the top of the skull, their labyrinthodont ancestors. Of these showing that this reptile had a very large

anapsids, the first to appear were reptiles "pineal eye"—an organ sensitive to light,

belonging to the order known as the Co- which still persists in a much reduced form tylosauria (ko-TiLE-o-sawr-e-ya), of which in the recent lizards and the tuatara

group Seymouria is perhaps the most primi- (Sphenodon) of New Zealand. tive, though not the earliest representative. Closely related to the American The cotylosaurs evolved through Permian diadectids were the Permian pariasaurs and Triassic times and then become extinct. (par-EYE-a-sawrs) of South Africa and Their evolution was divided along three Russia. These were really massive reptiles, lines of development. First there were the as big as small cattle. Like the other large small primitive forms of Carboniferous and cotylosaurs they were seemingly plant Permian age closely related to the "grand- eaters, large, heavy, and sluggish. They had

50 very broad, robust bodies and strong, heavy where they had become specialized to the ex- legs, and as in other primitive anapsids tent that in some of them there were spikes there was no clearly defined neck. on the sides or the back of the skull. The last of the cotylosaurs, living through Finally, the Middle Triassic of Scotland Triassic times, were diadectomorphs which and the Upper Triassic of New Jersey yielded were smaller than the large Diadectes of the most highly specialized procolophonids, North America and the massive pariasaurs of the last of the cotylosaurs. They were charac- Europe and Africa. Their development ran terized by a flattening of the skull and an ex- counter to the earlier trend towards giantism cessive development of the spikes on the in this branch of the cotylosaurian reptiles. sides and the back of the head. As in the Known as procolophonids after the charac- other diadectomorphs, the pineal "eye" was teristic genus Procolophon (pro-KOL-o-fon), large. The teeth had become far fewer but these animals evidently ranged widely were highly specialized, for the back teeth throughout the world in Triassic times, were broad, sharp chisels, evidently use- since they are found in South Africa, central ful for chopping and cutting food. A

Europe, Scotland, and North America. particularly fine specimen is the almost

An early type of procolophonid is to complete skeleton of Hypsognathus (hips- be found in the Lower Triassic genus, og-NATH-us), recently discovered near Procolophoti, of South Africa. Although Passaic, New Jersey, and now in the Ameri- small, Procolophon was robustly con- can Museum of Natural History. structed. It had a deep skull, narrow in the With the passing of the procolophonids, front and broad at the back. The pineal during the late stages of Triassic history, opening on the top of the skull was very the cotylosaurs became extinct. They had large. The teeth were limited in number, lived out their evolutionary life span—they and those in the back portion of both upper had to give way to the more highly de- and lower jaws were somewhat broadened veloped reptiles of later Mesozoic times. for chopping or cutting green plant food. Such were the beginnings of the reptiles. In Lower Triassic times the procolo- Let us now follow their interesting evolution phonids appeared also in central Europe through its many ramifications.

A LARGE PARIASAUR, Scutosaurus, from the Permian beds of Russia, showing an early trend to giantism in the reptiles. This animal was as large as

an ox and perhaps heavier, but it retained a primitive form. Notice the pro- portionately small head, the out-bowed legs, and the clumsy body

Restoration by John C. Germann

7 The Mammal-like Reptiles

""'; t must not be thought that during the the face of the earth, for their remains are p early days of reptilian evolution in found on all of the major continents. Their h Permian and Triassic times, the primi- evolutionary record, however, is confined tive anapsid reptiles, the cotylosaurians, for the most part to North and South

had the world all to themselves. The laby- America, eastern Europe, and South Africa. rinthodont amphibians presented a certain The subclass can be divided into two large amount of competition to these early rep- groups, the Pehjcosauria (pel-i-ko-SAWR-

tiles in the struggle for existence on the e-ya), found for the most part in the Upper land, but the really serious antagonists of Pennsylvanian and Lower Permian of North the anapsids were other reptiles, for this America, and the Therapsida (ther-APS- was the age when most of the great evolu- i-da), mainly found in the Middle and tionary lines of reptilian development were Upper Permian and the Triassic of the Old

getting their start. The evolution of the World and South America. reptiles was mushrooming out, so that there Our knowledge of the pelycosaurs is de- was a strong overlapping of the evolution- rived mainly from fossils found in the ary generations. Grandfathers and grand- Permian red beds of Texas. These fossils children were living side by side. show that the pelycosaurs had their begin- One large division of the reptiles that nings as long, lizard-like reptiles, with arose, developed, and died out during the rather sinuous bodies and sprawling limbs.

early phases of reptilian life in the Permian (The term lizard-like is used here to con- and Triassic periods, was that of the vey a word picture. Such a term does not synapsids. These were the reptiles that, as imply any relationship with or ancestry to

shown by the drawings on page 49, were the lizards, for it was to be many millions

characterized by a lower opening in the of years before the first lizards made their skull roof behind the eye. appearance on the earth.) Varanosaurus The history of the synapsids was, geo- (var-AN-o-sawr-us) was a form typical of the logically speaking, of comparatively moder- primitive pelycosaurs. From such a begin-

ate length. The first of these reptiles made ning the pelycosaurs developed along their appearance about 250 million years several radiating evolutionary branches. ago in Pennsylvanian times; the last of their In Varanosaurus the basic structural

kind had disappeared by the end of the pattern for the pelycosaurs was set, that of Triassic period, 80 million years later. elongated, sprawling-limbed, four-footed

Nevertheless this is one of the most im- reptiles. Evolution in these animals was portant reptilian groups, because from cer- mainly a process of skull and backbone

tain branches of it there sprang the mam- modifications. mals, the warm-blooded furry animals that Some of the pelycosaurs grew large, and subsequently were destined to inherit the the skull deepened. They had numerous earth. sharp teeth, the design of which indicates The synapsids were widely spread over that these were fish-eating animals, a sup-

53 •^^ The family tree of the reptiles: a pic- torial diagram summarizing the history of the reptiles as discussed in the following pages Restorations by John C. Germann 54 ^ The evolution of the synapsid reptiles. As seen here, they showed wide variation in form, but their relation-

ship is always indicated by the skull pattern shown on page 49

Restorations by John C. Germann position that is strengthened by the fact cording to one idea, the long spines on the that these reptiles are found in stream de- vertebrae of Dimetrodon afforded a pro- posits together with the remains of fishes. tection for the spinal column—a protection Such was Ophiacodon (o-fee-A-ko-don). against the attacks of savage enemies. The

Certain pelycosaurs evolved tremen- only thing wrong with this theory is that dously long spines on the vertebrae, spines there were no other large, active carnivo- which in life must have supported a mem- rous reptiles at that time to prey upon branous sail that ran down the middle of Dimetrodon. Dimetrodon was the lord of the back. These were the sphenacodonts or his small universe, he was one of the largest finbacks, typified by the genus Dimetrodon and certainly one of the most active and (dye-MET-ro-don), a good-sized reptile, six predaceous of the animals living in Texas or seven feet in length. Dimetrodon had a during Permian times. Another idea had it deep skull, armed with many cruel, dagger- that the "sail" of Dimetrodon really was a like teeth. The sail on the back was tall, sail, that this animal ventured out onto the thrusting up two or three feet above the surface of the Permian lakes and rivers, line of the backbone. scudding along before the wind, tacking

What was the purpose of this huge sail, back and forth in a fashion approved in the seemingly so cumbersome, and certainly a best yachting circles. Such a theory is, of serious drain upon the blood supply and the course, one on the ridiculous side. energy of the animal? Much thought and Perhaps the truth is that the sail of discussion has been given to this problem, Dimetrodon is not to be explained upon any with suggestions ranging from the not-so- functional grounds. It may very well be sublime to the downright ridiculous. Ac- that this represents an unbalanced growth,

This grotesque "sail" has been a subject of much conjecture. Probably it is merely a case of hereditary maladjustment. In this Permian scene of over

200 million years ago, Edaphosaurus is fleeing from his flesh-eating relative Dimetrodon (in the background). Both were about five or six feet long

Restoration by John C. Germann that it is an example of heredity "gone The mammal-like reptiles had their be- wild." The ophiacodonts, for instance, had ginnings in small synapsids known as rather tall spines on the vertebrae, spines dromasaurs, from which they radiated that served for the attachment of strong through later Permian and Triassic times muscles to help hold up and stiffen the along two general lines of adaptation. One back. It may be that there was some sort of of these evolutionary lines followed a trend a hereditary upset, so that the spines toward the development of bulk. The other elongated much faster than the animal line was one in which highly advanced and grew, and since this strange adaptation was correlated structural features appeared, as not particularly deleterious, the animal will be shown below. survived in spite of it. We frequently see The large heavy therapsids appeared in such developments in nature. the Permian and became dominant ele- For instance, there was a herbivorous ments in the animal assemblages of their pelycosaur, known as Edaphosaurus (e-DAF- day. These animals developed along two o-sawr-us), in which the spines were not lines, one known as the Dicynodontia only elongated but equipped with numer- (dye-siNE-o-dont-e-ya), the other as the ous transverse processes, like the yardarms Dinocephalia (dye-no-sef-A-lee-ya). The of an old square-rigger. It is certainly diffi- dicynodonts were exceedingly numerous cult to assign any functional purpose to and rather varied. Some were compara- such a development. It is much more logical tively small, others were very large, as to assume that this peculiar growth was merely a case of a hereditary maladjust- ment. The pelycosaurs are extraordinarily in- The Permian reptile Moschops, as it might have appeared in South Africa some 200 mil- teresting to us, not only because of the lion years ago. This animal typifies the large bizarre adaptations shown some of them, by plant-eating Therapsids of South Africa but also because some of these animals, Restoration by John C. Germann particularly the sphenacodont-like forms, were the ancestors of those synapsid rep- tiles known as therapsids. The therapsids were the "mammal-like reptiles," a descrip- tive term that delineates not only their general appearance but also their morpho- logical relationships, for these were the reptiles that were in part actually the direct ancestors of the Mammalia, that division of the animal kingdom of which we are members.

The therapsids are found in many locali- ties in the several continental areas, but it is in South Africa and in Russia that our evidence for the past history of these ani- mals is especially complete.

56

"* I QA bulky as present-day oxen. But all of them, spikelike teeth in the upper jaw. The skull whether large or small, seemingly were itself was modified so that the bones of its rather active, for these reptiles literally back portion formed a series of strong "got up on their legs," the better to move arches, probably as attachments for power- across the land in which they lived. In ful jaw muscles. Dicynodon was typical. short, these animals could walk with their Although the preserved remains of feet underneath their bodies, so that the dicynodonts are particularly abundant in legs could be brought in for support against South Africa, it is evident that these animals the constant downward pull of gravity. had a cosmopolitan distribution. Stahlekeria

Perhaps the most striking feature of the (stal-le-KER-e-ya) is a giant dicynodont dicynodonts was the specialization of the found in Brazil; other dicynodonts are skull, for in these animals the head had known from North America, China, and undergone a profound transformation. The Europe. upper and lower jaws were beaklike in The dinocephalians were rather similar form. The teeth were usually lost, except in to the dicynodonts in body form. They were the males, which retained two enlarged large, powerful reptiles with strong limbs. The back sloped giraffe-fashion in typical members of the group, as for example in Moschops (Mos-kops). Considerable variety was shown in the adaptations of the head in these animals. Some of the more primitive forms, like

Titanosuchus ( tye-tan-o-sooK-us), were carnivorous, with elongated faces and sharp, dagger-like teeth. Certain specialized types, such as Moschops, were vegetarians, between the reptilian upper and lower with rather weak jaws and peglike teeth. jaws to form, surprisingly enough, two of They all had very heavy thick skulls, and the chain of three bones in the mammalian as a group were remarkable for the great middle ear.

development of the light receptor, the One of the most striking features in the pineal organ or "eye" on the top of the skull of the theriodonts was the specializa- head. Of course they had the usual pair of tion of the teeth. In most reptiles the teeth eyes as well. are all more or less alike, and they keep

From our own anthropocentric viewpoint coming in during the life of the animal as all other reptiles pale into insignificance as fast as their predecessors are worn away compared with the theriodonts (ther-c-o- or broken. In the theriodonts, however, donts). These were the mammal-like rep- there were some small front teeth, evidently tiles par excellence, and as has already been for nipping and grasping, some large, broad said they were indeed the ancestors of our back teeth, evidently for chewing or grind- own blood kin, the mammals. ing, and between them some elongated, The theriodonts, of which Cynognathus dagger-like teeth, evidently for slashing (sine-og-NATH-us) and Bauria (BOWR-e-ya) and tearing. Here we see an exact counter- were typical, were for the most part rather part to the front incisors, the long, pointed small or medium-size carnivorous reptiles, canines, and the grinding teeth (the pre- and like the other therapsids they had the molars and molars) of the mammals. More-

body lifted up off the ground on strong legs over, there is every reason, from the evi-

—a sign that these were active animals. dence of the fossils, to think that the differ-

They had long, rather doglike skulls, which entiated teeth in the theriodonts were di- in their entirety show features directly rectly ancestral to the differentiated teeth antecedent to those of the warm-blooded, of the mammals. Also, the evidence indi- furry mammals. Thus in many of the theri- cates that the manner of tooth succession in odonts there was a double ball-joint or certain theriodont reptiles led finally to the condyle that accommodated the rotation condition typical of mammals, in which of the head on the neck as in the mammals, there are but two sets of teeth, milk or whereas most of the reptiles have a single deciduous, and permanent. ball-joint. In the theriodonts there was a It is not, however, the evidence in the secondary palate as in the mammals, sepa- skull and teeth alone that points to the di- rating the nasal passage from the throat, a rect descent of mammals from the theri- distinct advance over the typical reptilian odont reptiles. For in these remarkable conditions. In the theriodonts the bone in reptiles the vertebrae of the backbone, the the lower jaw that bore the teeth was shoulder blade, the hip bones, the limbs, greatly enlarged, while the other bones and the feet all show many characteristics were reduced—again an approach toward that clearly foreshadowed the typical mam- the mammalian condition. And correlative malian plan. with this development there was a fore- Such is a composite picture of a true shadowing of one of the most remarkable "missing link," one of the very important transformations in evolutionary history, the stages in the history of vertebrate evolu- shifting of the two bones forming the joint tion, the link between the cold-blooded

58 reptiles, which for so many millions of years ants, the mammals, continued the germ of were the undisputed rulers of the earth, life, carrying on and perfecting the pattern and the warm-blooded mammals which first laid down by the theriodonts. Thus it were destined to supplant them. may be said that the theriodonts, in evolv- By the end of Triassic times the mam- ing as they did, sealed their own doom. mal-like reptiles, and more particularly the Indeed, they sealed the doom of the entire theriodonts, had gone through their course reptilian world, for they were the progeni- of evolutionary development and had be- tors of a race that was destined to wrest come extinct. Yet they did not in all re- the control of the land and the waters and spects become extinct, for their descend- the air from them. Yet the doom of reptilian dominance was not to come until future ages in the geologic

story. The first mammals, the descendants y A type of reptile that stood close to of the theriodonts, appeared in the Triassic, the ancestry of mammals: the flesh-eating some 200 million years ago, but the therapsid reptile Cynognathus, an active and through predaceous animal millions of years that constituted the Juras- Restoration by F. L. Jaques sic and Cretaceous periods the descendants

of these first mammals played a relatively

insignificant part in the economy of life.

The world still belonged to the reptiles; in

fact, it was during the lush days of Jurassic and Cretaceous times that the reptiles rose to the greatest heights of their long histoiy on this sphere. Those were the days of the dinosaurs, when there were giants on the earth.

59 8 Ancestors of the Dinosaurs

3 HE REIGN OF THE DINOSAURS Was temporal openings, an upper one and a founded some 200 million years ago lower one, separated each from the other by i in Triassic times, the first division of bars of postorbital and squamosal bones. the Mesozoic era. The last of the laby- From an ancestry typified by reptiles such rinthodont amphibians were seeking refuge as Youngina the diapsids evolved in vari- in such streams and ponds as they could ous directions during Mesozoic times, to find, primitive turtles were continuing the become the dominant land animals of that history of the ancestral, roofed-skull rep- great era of Earth History. The differentia- tiles, and the active, mammal-like reptiles tion of the several lines of diapsid develop- were ranging across the land in search of ment was largely achieved during the

their food. At that time the dinosaurs made Triassic period, and it was then that the their earliest appearance on the earth. Yet even though the lines of dinosaurian radia- tion became established in the Triassic pe- riod, the story of these great reptiles begins still further back in geologic time, in the distant days of the Permian, when the first diapsid reptiles made their debut on the stage of Earth History. The 225-million-year-old records of The skull of a primitive diapsid reptile, Permian diapsids are rather scanty. Per- Youngoides, from the Permian of South haps the best evidence as to the nature of Africa these forerunners of a great line of evolu- Redrawn after Olson and Broom tionary development is to be found in the little reptile, Youngina (young-EYE-na) or its close relative, Youngoides (young-OY-deez) most important diapsid stem was estab- from the upper Permian rocks of South lished. This was the order of reptiles known Africa. as the Thecodontia (theek-o-DONT-e-ya)— Youngina was small, and generally lizard- more commonly called the thecodonts—the like in appearance. (Please remember that ancestors of certain dominant Mesozoic this is a comparison, and is not intended to reptilian groups, notably the dinosaurs, the suggest any relationships with the lizards, flying reptiles, and the crocodilians. which appeared at a much later stage of The thecodonts had narrow, deep skulls, geologic history.) Youngina had a long a trend of development that was fore- body and slender limbs. The head was shadowed in Youngina and was well estab- pointed and the jaws were armed with lished in the early Triassic forms. In these sharp, needle-like teeth. The key to the rela- reptiles there was an opening on either tionships of this animal is, of course, in the side of the skull, in front of the eye. This hack portion of the skull, which had two opening, or fenestra, seeminglv contributed 60 limbs, . to the lightness of the skull, for in the and there has been a retention of thecodonts and their descendants the skull the four-footed method of walking. In the was in general light, yet strong and well thecodonts, on the contrary, there was an braced. early adaptation for two-footed locomotion. In addition, the pineal opening or "eye," These animals rose up on their hind limbs. so characteristic of the early reptiles, had There was a division of labor between the disappeared. Finally, so far as skull char- two sets of limbs; the hind legs became acters are concerned, the thecodonts were long and strong, for rapid running, while typified by the limitation of the teeth to the fore limbs became very much reduced the edges of the upper and lower jaws; in and handlike, to be used for grasping. Such other words, there were no teeth on the a profound change in the posture of these palate, as was so often the case among the reptiles naturally was reflected in their more primitive Paleozoic reptiles. bodily structure. It was, however, in the pose and the The body, instead of being supported manner of progression that the thecodonts fore and aft in the usual fashion, was

developed their greatest difference from all "slung" at the hip joint, so that this joint other reptiles. We have seen in the fore- became a sort of fulcrum on which the

going pages how the first land-living verte- movements of the entire animal were piv-

brates—the early tetrapods (TETT-ra-pods) oted. There was a long tail, to serve as a

evolved from certain fish, and how during counterbalance for the body. The hip gir- the course of this evolution the four paired dle or pelvis necessarily became strong, for

fins of the fish were transformed into four it had to develop a long, stout articulation supporting limbs which enabled the animal with the backbone as well as a deep socket to progress on land. Now in many of the to accommodate the ends of the upper leg

reptiles the evolutionary specializations bones. Therefore it became in the primitive that have taken place have involved a diapsids a triradiate structure, serving ad- strengthening or a modification of the four mirably as a strong connection between the body and the hind limbs,—to take the stresses and strains that are inherent in a partially upright pose. Of the primitive thecodonts none were more characteristic than Euparkeria (yoo- park-ER-e-ya) from South Africa, or Orni- thosuchus (ortN-i-tho-sooK-us) or Saltopo- suchus (sal-to-po-sooK-us) from Europe.

When we look at one of these little reptiles, we see the ground plan for the dinosaurs. Let us therefore look at them carefully and remember them, for an understanding of

this ground plan is the key to the under- The ancestors of the dinosaurs, the thecodonts, took to their hind legs standing of the dinosaurs. It is the blueprint and developed this special type of hip to dinosaurian body form. girdle One group of thecodont reptiles became

61 FROM THIS SORT OF PATTERN, all of the varied dinosaurs developed: the skeleton of Saltoposuchus, a Triassic thecodont rep- tile only about four feet long Modified from von Huene

specialized in an interesting manner. These such hapless animals as might come within were the reptiles known as the phytosaurs their reach, and crawling out on the sandy

(FiTE-o-sawrs), which, like all thecodonts, bars and banks to sun themselves. The lived in Triassic times. The phytosaurs are phytosaurs had a very crocodile-like ap- found in various parts of the earth, particu- pearance, not only in the body but also in larly in Europe, Asia, and North America. the head itself; indeed, to a casual eye, the Whereas the primitive thecodonts were skeleton of a phvtosaur might easily be small, the phytosaurs were rather large, mistaken for one of a crocodile. The most ranging in size from six to 20 feet or more noticeable difference is that in the phyto- in length. And while the primitive theco- saur the nostrils are located on the top of donts were mostly two-footed, the phyto- the head, immediately in front of the eyes, saurs were four-footed. It is perhaps sig- rather than at the tip of the snout as they nificant, however, that even in these four- are in the crocodiles. It should be empha- footed phytosaurs, the front limbs were sized here that in spite of this similarity of noticeably smaller than the hind limbs. appearance between the phytosaurs and the The return of the phytosaurs to the primi- crocodiles, they were quite distinct groups tive four-footed mode of life was only one of reptiles. The phytosaurs were not the phase of their adaptation, for these were ancestors of the crocodiles. semi-aquatic reptiles. They lived a croco- Here is a prime example of parallelism dile-like existence in the streams and lakes in evolution,—the similar development of of the Triassic landscape, spending most distinct but related animals. The phytosaurs of their time in the water, preying upon were like crocodiles, at a time when croco-

62 diles had not yet evolved. Perhaps it might "ecologic niche," both groups played the be more accurate for this reason to say that same role in life history at the time in the crocodiles are like phytosaurs; the phy- which they lived. In each case these were tosaurs came first and then died out—the highly predaceous, water-loving reptiles crocodiles then appeared and evolved in a that made their way in life by hunting. fashion that imitated to a remarkable de- The phytosaurs, like the crocodiles of to- gree the development of the phytosaurs. day, were the scourge of their environment. This parallelism between the phytosaurs They feared nothing; they were the stealthy and the crocodiles was due to the fact that foes of whom all other animals of that day both groups of reptiles occupied the same had to beware.

THE PHYTOSAURS resembled crocodiles but were not their an- cestors. They lived the same kind of life as crocodiles but did not survive beyond the end of the Triassic period, about 155 million years ago, before the crocodiles evolved in a parallel direction. Notice the nostrils immediately in front of the eyes. (Genus Machaeroprosopus, from Arizona)

Restoration by John C. Germann

v 4J

63 9 The Kinds of Dinosaurs

I ll of this time it has been our the remains of large land-living reptiles j/y purpose to get some idea of the found in rocks of Mesozoic age. Only later evolution that did it that the dinosaurs I course of reptilian become apparent went before the development of the dino- belonged to two quite distinct orders of saurs, not only to give us a background for reptiles, as distinct from each other as, for the proper understanding of dinosaurian instance, cattle and horses. So the term evolution, but also because the Permo- "dinosaur" assumed a general rather than

Triassic history of the reptiles was in itself an exact meaning. Even so, it remains a highly important in its bearing upon the useful name. It indicates a large category

later history of life on the earth. of prehistoric beasts, but it is a "loose" term. In the last chapter we had a glimpse of It may be compared with "hoofed animals" the immediate diapsid ancestors of the di- or "ungulates," the suitable term used when nosaurs, how they developed, and in which we wish to speak about our modern cattle directions their evolutionary progress led and horses in one breath. them. Now we are ready for the dinosaurs Two great orders of reptiles made up the themselves. dinosaurs. These were the "Saurischia" and As has been mentioned, the dinosaurs the "Ornithischia," names which mean were diapsid reptiles, characterized by the merely "reptile hips" and "bird hips." The two openings on each side of the skull be- Saurischia (sawr-iss-kee-ya) were those di-

hind the eye. Now it will probably come nosaurs having the three bones of the hip as a distinct surprise and perhaps a dis- arranged more or less according to the typi- appointment to the reader to learn that the cal reptilian plan, while the Ornithischia word "dinosaur" does not denote a single (orn-ith-iss-kee-ya) were those dinosaurs and natural group of reptiles, but rather in which the bones of the hip resembled in two quite distinct reptilian orders. Why their arrangement the pelvis of birds.

then all this glib talk about "dinosaurs" if This is the primary, fundamental division in using this term we are not utilizing a of the dinosaurs, extending back to the be- precise or definite name? ginnings of dinosaurian history. All of the

The explanation is relatively simple. In dinosaurs had a common ancestry, in that

the first place, dinosaurs were virtually un- they were all descended from certain theco-

known only a little more than a hundred dont reptiles. But once the separation be-

years ago. When first the bones of these tween the saurischians and ornithischians animals were studied by scientists in Eng- was established—and that came about dur- land and in Europe, there was no term to ing Triassic days—these two groups of indicate them collectively. Then in 1842 reptiles remained quite distinct from each the great English paleontologist and other.

anatomist, Sir Richard Owen, invented the It is this structural plan of the pelvis and name Dinosauria, from the Greek deinos, of other parts of the skeleton as well that "terrible" and sauros, "lizard," to apply to distinguishes the two orders of dinosaurs—

64 no other standard will suffice. For instance, following page. it is a common misconception to suppose It is a picture in which we see the perfec- that dinosaurs were all huge reptiles, carry- tion and modification of the basic thecodont ing their heads high in the clouds, and plan, the plan which had for its foundation borne on stout legs having the general di- a two-footed posture, a deep, light skull, mensions of small redwood trees. Nothing and a carnivorous diet, with all of the im- could be more erroneous. Some of the di- plications of hunting and rapid movement nosaurs were large, but others were very imposed by such a diet and by such a small. Indeed, there are some dinosaur mode of life. skeletons that are hardly more than a foot Two trends are to be seen in the develop- in length; others are no larger than rabbits ment of saurischian and ornithischian adap- or turkeys. But given the structural pattern, tations from a thecodont ancestry. One of the pattern that was established in the these was the general trend towards an

Triassic thecodonts, the saurischian and increase in size. The ancestral thecodonts ornithischian dinosaurs can all be ade- were small reptiles; many of the later dino- quately defined and the picture of dino- saurs were comparatively large—though saurian evolution limned. This picture in this is not invariably the case. The other simplified form is given in the chart on the was the trend towards a modification of the

65 The two-footed ancestors of all the < dinosaurs, the Thecodontia, gave

rise to two main orders of dinosaurs

and six suborders, as shown above THECODONTIA Ancestors of all dinosaurs primitive or ancestral, two-legged posture —a very marked trend in the dinosaurs. Dinosaurian Structure and Relationships Only in the persistently carnivorous thero- Some Details of pods was the purely two-footed pose of the SAURISCHIA ORNITHISCHIA thecodonts retained. In all of the other theropods saurischians and ornithischians there was a definite drifting away from the ancestral carnivorous mode of life, and from the bi- yornlthopods X pedal pose. The sauropods and most of the ornithischian dinosaurs became large plant- stegosaurs ceratopsians eaters. A big bulky animal would be at an ankylclosaurs obvious disadvantage in attempting to carry himself about on two legs; consequently Primitive reptiles these dinosaurs came down on all fours.

But it must be remembered that this was a secondary return to the primary four-footed pose, and this can be seen because the front

y The small theropod dinosaur Ornitholestes, represented in the act of catching the first known bird, Archaeopteryx. Its food probably consisted mostly, however, of other small reptiles, eggs, insects, and the like. Ornitholestes preserved many of the features of the ancestral dinosaurs. From animals similar to this the great carnivores and sauro- pods evolved Restoration by Charles R. Knight legs of even the most completely four- dinosaur was his giant contemporary, the footed of these animals were almost always huge theropod known as Allosaurns (al-lo- noticeably the smaller. The heritage of the sawr-us), one of the mighty hunters of the ancestor was retained in the descendant. Jurassic, an animal some 35 feet in length that swung across the landscape in majestic Saurischia and awful splendor. In a sense Allosaurus was an enlarged edition of his little relative, Theropoda (The carnivores) Ornitholestes, for this giant was a two- The theropods (THER-o-pods) preserved legged meat-eater. But giantism in nature more completely than any of the other di- is more than a simple process of something nosaurs the primitive characteristics of their little being reproduced on a large scale, for thecodont heritage. They remained the true with size there come many mechanical two-leggers, and for the most part they problems of weight and accompanying were flesh-eaters. stresses and strains, so that the big animal In such persistently small animals as the shows many changes in proportion and Jurassic Ornitholestes (orn-i-tho-LES-teez) many differences in structure as compared we see a general retention of ancestral di- with the little animal. nosaurian features. Ornitholestes was no Thus Allosaurus had relatively very more than five or six feet in length—and heavy, strong hind limbs, to carry its great this includes the long, attenuated tail which weight. And as a corollary to the strains served as a lever to balance the weight of consequent upon size, the entire pelvis in the body. All in all this was a remarkably this animal had become strong and heavy light and graceful little dinosaur, with for the attachment of the powerful muscles strong, birdlike hind limbs, on which it that moved the hind legs. could probably run through the dense tropi- The hands of this great meat-eater were cal greenery with considerable swiftness armed with hooklike claws, a development and agility, darting in and out in search in keeping with the size and the violent of its prey. The front limbs of Ornitholestes mode of life which this hunter must have were relatively small as in all the theropods, led. Perhaps the greatest difference to be and there were long, grasping fingers with noted between the small carnivore and the which this little animal could hold its food. large carnivore is to be seen in the huge The skull, too, was small and light, deep head that was carried by the giant Allo- and narrow, and armed with sharp teeth saurus. Here was a large skull which in well adapted to biting and tearing. On the spite of its size was remarkably light and whole this was an efficient little mechanism strong, and possessed a widely gaping for the catching of Jurassic small fry, and mouth armed with dagger-like teeth. This thus Ornitholestes fulfilled his role in the was the business end of the beast. Allo- ecological or environmental scene of that saurus was the hunter of big game, and as day. This was the seeker of small game, of such he must needs be provided with weap- other ground-living reptiles that hid in the ons sufficient for the task—that is, with shelter of rock crannies or climbed up the large, strong jaws and heavy, sharp teeth. stems of ferns. He had them.

A decided contrast to this graceful little The culmination of development in the

68 ^ Allosaurus, a large predaceous y The largest carnivorous land animal that ever lived: theropod dinosaur of Jurassic age. Tyrannosaurus. This animal represents the culmination

It is represented here as devour- of meat-eating adaptations in the dinosaurs. It evidently ing the carcass of a brontosaur, one preyed upon some of the large herbivorous dinosaurs of the large dinosaurs on which it of its day and is here represented as attacking the horned probably preyed dinosaur, Triceratops

Restorations by Charles R. Knight theropod dinosaurs was attained by the There were other carnivorous theropods giant Cretaceous form, Tyrannosaurus (tye- living in Cretaceous times, similar to Tyran-

ran-o-SAWR-us ) , the "king of the dinosaurs." nosaurus but showing lesser degrees of spe- This was the greatest and most fearful land- cialization. One of these was the somewhat living carnivore that has ever dwelt on smaller form, Gorgosaurus (gor-go-SAWR- earth, an animal of magnificent proportions us). and terrible power, beside which the mod- A somewhat different line of theropod

ern lion and bear would appear as almost specialization is to be seen in the Creta- harmless dwarfs. Tyrannosaurus, standing ceous dinosaur, Struthiomimus (strooth-ee- on his powerful hind limbs, carried his head o-mime-us), the "ostrich dinosaur." This some 18 or 20 feet above the ground, while evolutionary line, alone among the thero- the distance from the tip of his nose to the pods, departed from the carnivorous mode

tip of his tail was all of 50 feet. This animal of life and turned to a vegetarian or perhaps

might have weighed some eight or ten tons a fruit-eating life. when he was a living creature of destruc- Struthiomimus was a dinosaur of medium tion. size, and like the other theropods was bi- The several specializations which charac- pedal, with a long tail to act as a counter- terized the upper Jurassic Allosaurus were balance to the body. The fore limbs were carried to extremes of development in the rather well developed and were provided

Cretaceous Tyrannosaurus. Thus, this giant with long-fingered, grasping hands, some- among the carnivores had exceptionally thing on the order of the hands in Ornitho- strong legs and a very stout pelvis to serve lestes. as a fulcrum between the backbone and the It is in the structure of the head and limbs. In Tyrannosaurus there was a reduc- neck that the "ostrich dinosaur" shows the tion of the fore limbs so that they had be- greatest departure from the typical thero- come inordinately small. Correlative with pod adaptations. In this reptile the neck this reduction of the forelimbs there was was very long, sinuous, and birdlike, as also a reduction in the hands, which were compared with the rather medium-length armed with hooked claws. The reduction or even short neck of most of the theropods, affected not only the size but also the num- while the head was small, and lightly built. ber of digits, so that only two claws were The skull in Struthiomimus was remarkable functional on each hand; evidently Tyran- not only for its small size and light construc-

nosaurus had little use for his arms. tion, but also because of the fact that all

That this was so is proved by the ex- of the teeth had been lost, while the jaws tremes to which the head developed in this were beaklike—again an ostrich-like adap- great dinosaur. The skull of Tyrannosaurus tation. It would seem that Struthiomimus was indeed a tremendous structure, power- lived a harmless and blameless life, eating fully built, with a mouth having a gape of such fruits or buds or insects that might almost unprecedented size and armed with come its way, with ever a wary eye cocked huge, scimitar-like teeth. Such was the of- on the big rapacious carnivores that ranged fensive weapon for this mighty hunter, a across the Cretaceous landscape. weapon that could be used with effect Sauropoda against other large and tough dinosaurs of that day. The sauropods (sAWR-o-pods) were the 70 ^ The Upper Cretaceous theropod, Struthiomimus. This dinosaur had gotten away from the active carnivorous habits of its theropod predecessors and become birdlike. The jaws developed as a flat horny beak that might be useful in eating fruits, other green things, insects, and small reptiles

Restoration by Erwin S. Christman

y One of the largest dinosaurs, Brontosaurus, a creature some 80 feet long and 40 tons in weight. It inhabited the marshes and streams of western North America between 120 and 155 million years ago and fed upon green plants in its tropical environment

Restoration by Charles R. Knight

S~&1. giants of the dinosaurian world and, so far animal, some 70 or 80 feet in length from as land-living animals go, the giants of all the nostrils to the tip of the tail, and like time. No other land animals have reached all of the typical sauropods it walked on the great bulk attained by some of the all fours. Much of the length of Bronto- sauropod dinosaurs, and only the huge saurus was taken up by the long tail, which whales in the sea have exceeded them. at its end was attenuated and whiplike, and

The beginnings of sauropod history may by the correspondingly long neck. Even so, be seen well exemplified by the Triassic the body was a huge, bulky affair weighing dinosaur Plateosaurus (plat-e-o-SAWB-us), in itself many tons, supported by great, found in Europe and Asia. This was a postlike legs. As in almost all of the four- dinosaur of medium size, some 20 feet in footed dinosaurs, the hind limbs were much length. It was characterized by its long tail larger and more massive than the front and by its rather long neck, surmounted by limbs, since as already mentioned the four- a comparatively small head. Plateosaurus footed pose in these animals was a second- had, of course, the typical three-pronged or ary development. The feet of Brontosaurus triradiate pelvis of the saurischians, and were short and broad, as would be neces- like its theropod relatives it was at least sary to support an animal of such bulk, and partially bipedal. In Plateosaurus there was they were armed with curved claws—one some enlargement of the fore limbs, which on each of the fore feet and three on each suggests that while this dinosaur may have of the hind feet. tramped across the Triassic landscape on its The head of this great reptile was re- strong hind limbs, it was nevertheless quite markably small compared to the body, and capable of assuming a four-footed posture it is difficult to imagine how an animal of for the purpose of feeding. The teeth were such size could take in through such a no longer the sharp blades so typical of the modestly-proportioned mouth enough green meat-eating theropods; rather they showed stuff to keep it alive. Yet there is no doubt a sort of flattening, and a blunting of their but that Brontosaurus was a plant feeder, points, as if they were becoming adapted and like all plant-eating animals it had to to the cropping and cutting of green, leafy consume a great amount of bulky material plants. in order to get sufficient nourishment to

It was in the Jurassic that the sauropod keep it alive and reasonably active. It must dinosaurs reached the culmination of their be remembered, of course, that these great evolutionary history. This was the period reptiles must have been rather sluggish, as of the giants, of Brontosaurus (bront-o- are the modern cold-blooded vertebrates, sawr-us), Camarasaurus (kam-ar-a-SAWR- so that they would not require as much us), and Diplodocus (dip-LAH-do-kus) in food to satisfy their needs as we might North America, of Cetiosaurus (seet-ee-o- think would be necessary. At any rate, we sawr-us) in Europe, and of the huge know that Brontosaurus did live and pros- Brachiosaurus (brak-e-o-SAWR-us) in Africa. per over a long period of geologic time, so

Brontosaurus is a typical sauropod and il- evidently he found his small mouth suffi- lustrates very well the characters of the cient for his purposes. group. All of the other sauropods represent varia- This dinosaur was a tremendously long tions of the pattern seen in Brontosaurus.

72 One well-known form from North America, saurischian forms. This is a fundamental

Diplodocus, was remarkably long and ta- truth which has its foundations in the basic, pering, although not so bulky as his cousin, diagnostic characters of these two great

Brontosaurtis. In this animal the skull was groups of dinosaurs. It will be remembered even smaller than in Brontosaurus, while that the saurischians were the forms with the teeth were weak pegs, no bigger in an essentially triradiate arrangement of the diameter than lead pencils. The nostrils of pelvic bones, similar to the arrangement in Diplodocus were located on the top of the the ancestral thecodont reptiles, while the

head, an adaptation for life in the water. In- ornithischians were those animals in which deed, the evidence would seem to indicate there was a rotation of the pubic bone so

that all of the sauropods spent much of that it came to occupy a position parallel their time in the water, wading around in to the ischium. This formation of the pelvis

swamps, and even venturing out into the is in itself an indication of the advanced deeper reaches of lakes or rivers to escape position of the ornithischians as compared from danger. with the saurischians.

The largest of all the sauropods was The argument extends to other parts of

Brachiosaurus which is found on opposite the body as well. In particular the or- sides of the world, in North America and nithischian dinosaurs showed specializa- in east Africa. This dinosaur was not so tions of the head and of the teeth, which

long as Brontosaurus or Diplodocus but it went far beyond the specializations to be was very bulky. In Brachiosaurus there was seen in their more conservative saurischian

a strange enlargement of the front part of cousins. It is interesting, too, to see that the the body, so that the fore limbs were larger Saurischia had gone through the major than the hind limbs (an exception to the phases of their evolutionary development general rule), while the neck was very long during Jurassic times, so that the saurischi- and heavy. This caused the back to slope ans of the ensuing Cretaceous period were giraffe-fashion to the hind limbs, while the for the most part continuations of "Jurassic tail was comparatively short. Brachiosaurus patterns." The Ornithischia, on the other had the nostrils raised on a sort of dome hand, experienced by far the major part or eminence on the top of the head, an of their evolutionary development in Creta- indication, along with the long neck and ceous times. raised fore-quarters, that this dinosaur The least "advanced" of the ornithischian probably waded along the bottom in deep dinosaurs are to be found among the large

water, where it was enabled by its great group known as the Ornithopoda (orn-i- size to thrust the top of the head above the THO-pod-a), the duck-billed dinosaurs and surface, periscope fashion, to breathe and their relatives. This is not to say that all to survey the surroundings. ornithopods (oRN-i-tho-pods) were of a par- ticularly primitive aspect—indeed, in some Ornithischia of the Cretaceous forms we see highly spe- cialized types. But there was one group of Ornithopoda the ornithopods that was relatively unspe- The ornithischian dinosaurs were on the cialized—the group known as the campto- whole more highly evolved than were the saurs.

73 ^ Camptosaurus: One of the first of mored dinosaurs, duck-bills, and the ornithischian dinosaurs, which horned forms were derived from an- lived in late Jurassic and early Cre- cestors something like this five- to taceous times. All of the later ar- eight-foot plant-eating dinosaur The camptosaurs or iguanodonts ap- In 1822 some peculiar teeth were found peared about 140 million years ago in the in Lower Cretaceous rocks in the county of Jurassic period, and they continued their Sussex, England, by the wife of Dr. Gideon development through Lower Cretaceous Mantell, a famous English paleontologist. times. These dinosaurs were bipedal, al- Of course nobody at that time had ever "di- though it is an interesting fact that the heard of a dinosaur, in fact the name camptosaurs did not lead a completely two- nosaur" had not yet been invented, so it footed ambulatory existence as did the was indeed a puzzle as to what the strange carnivorous theropods. For the camptosaurs teeth found by Mrs. Mantell might be. were perfectly capable of coming down on Mantell, unable to identify the teeth to his

all fours whenever the occasion demanded satisfaction, sought the advice of Sir Charles such a pose, which was probably quite Lyell, who in turn submitted the specimens often the case. to Baron Georges Cuvier, the celebrated In Camptosaurus (kamp-to-SAWR-us) the French anatomist. Cuvier, after due delib-

skull was rather long and low, with flat- eration, announced that these teeth be- tened, bladelike teeth—obviously intended longed to a rhinoceros. for the cutting and chewing of green plants. That didn't seem right, so Mantell went In these animals there were no teeth in the back to look for more remains, and found front of the mouth, either above or below— some bones in the quarry where the original a basic pattern that was repeated in virtu- discovery was made. There was some more

ally all of the ornithischian dinosaurs. In- guessing by Cuvier— this time he voted in stead, the front of the jaws formed a bird- favor of a hippopotamus—but finally, after

like beak, which in life was obviously cov- diligent comparisons, Mantell himself ered by a horny sheath and served as an finally came to the conclusion that here was efficient mechanism for the biting and cut- a new type of reptile, of large size, and

ting of plant food. It should be repeated with teeth like those of the present-day

here that all of the ornithischians were iguana. Hence the name, Iguanodon. strictly herbivorous. At first Iguanodon was restored as a One of the very interesting dinosaurs, four-footed reptile, but in later years an

which unfortunately is not to be found in unusual series of seventeen skeletons was

any of the American museums, is the Euro- found in a coal mine in Belgium, and the pean ornithopod, Iguanodon (i-GWAN-o- true nature of this dinosaur was recognized. don). Iguanodon, a close relative of Camp- The ornithopods reached the height of

tosaurus, is of particular interest not only their development in the Cretaceous hadro-

because it is a well-known animal of which saurs or trachodonts, often called the "duck- numerous complete skeletons have been billed" dinosaurs. These were large dino-

discovered, but also because it was the first saurs, partially bipedal and partially dinosaur to be scientifically described. quadrupedal, and they were obviously water-loving animals. This is shown by the structure of the head, in which the front •^^ Trachodon, a duck-billed dinosaur of late Cre- of the skull and jaw were broadened into taceous times. The duck-bills were all aquatic and spent much of their time either in or near the water a flat "duck bill" (hence the sobriquet) that Restorations by Charles R. Knight was most assuredly very handy for grovel-

75 THE STRANGE HEADS OF SOME DUCK-BILLED DINOSAURS

Restorations by John C. Germann

ing in the shallow water and muddv bot- Kritosourus toms of streams and ponds. It is also shown

by webbing between the toes, revealed in An expansion of the natal bones gave Kritotaurut several cases where skin impressions of beaked or hook-noted appearance a these animals have been preserved.

The central type is Hadrosaurus (had-ro- sawr-us) or Trachodon (TRAK-o-don), found in various parts of western North America and in the eastern portion of the continent,

too. Indeed, as already mentioned the first dinosaur skeleton to be found and described in North America was a Hadrosaurus skele- ton, discovered not in the wilds of the west- Corythosaurus ern badlands, but in the town of Haddon- field, New Jersey, a suburb of Philadelphia. A glance will show that Trachodon was a

A large crett. Involving the premaxlllarlet a* well at camptosaur grown large, in which the skull dittingulthod Corythotaurut. The long the natal bonat, was flattened, especially in front, to form S-shaped curve of the natal pattaget formed within the broad "duck bill" so characteristic of the crett an air ttorage chamber permitting the animal to remain under wafer longer these dinosaurs. In late Cretaceous times there were nu- merous evolutionary variants of this central hadrosaurian theme, developments charac- terized for the most part by peculiar and bizarre modifications of the skull. One of these was Kritosaurus (kritt-o-SAWR-us). An- other was Corythosaurus (kor-ith-o-SAWR- us). Another was Lamheosaurus (lamb-e-o- sawr-us). Another was Parasaurolophus Lambeosauruj (par-a-sawr-AH-lof-us). Suffice it at this point to note the strange and wonderful lengths to which evolution The crett prelected behind the tkull In Lambeotaurut, carried these fascinating dinosaurs. On page In addition to forming a tort of hatchet-thaped blade on the top of the tkull 87 we refer further to the significance of the peculiar skull structure of the several tvpes of hadrosaurian dinosaurs. A very peculiar group of ornithopod di- nosaurs was that of the troodonts (tro-o- dahnts), small to medium-size dinosaurs, in which the body seemingly was rather simi- lar to the body of other ornithopods, but in which the head was remarkably special- ized. In these dinosaurs the roofing bones of Parasaurolophus

i 76

and premaxillary bonet, reached the extreme develop- ment. In thit crett, the greatly elongated natal pattage the skull became extraordinarily thick, so and the ankylosaurs of the Cretaceous. that there was a dome of solid bone above Stegosaurus (steg-o-SAWR-us) was typical the brain, while on the nose and at the of the Jurassic pattern of dinosaurian armor. back of the head there was a fearsome ar- Here was a rather large ornithischian, com- ray of nodes, points, and spikes. The ex- pletely quadrupedal, but with the fore treme was reached in one of the late Creta- limbs so much smaller than the hind legs ceous troodonts, Pachijcephalosaurus (pak- that this animal was a congenital "high- e-SEF-a-lo-sawr-us), having a solid domed behind." From the tiny camptosaur-like skull roof some nine inches thick. This was, head, carried rather close to the ground, indeed, the original bonehead! the back arched in a steep curve to the high hips, and then descended again to the tip Stegosauria of the tail. The massive body was supported There were two groups of ornithischian by strong legs, ending in broad padded feet. dinosaurs which during the course of their The "armor" of Stegosaurus was perhaps development were distinguished by a the most striking feature of this strange

"hands off" trend of evolution. These were dinosaur, and it contributed much to the the so-called armored dinosaurs, the walk- strange appearance of the beast. Down the ing fortresses that defied their enemies by middle of the back there was a series of the comparative impregnability of their upright, triangular plates, arranged alter- defense—the stegosaurs of the Jurassic nately, while the tip of the tail bore four

Stegosaurus, an armored dinosaur of the Jurassic period. Some of the earlier restorations showed this animal with the plates paired, and with six tail-spikes, but the arrangement of alternating plates with four

spikes on the tail, shown here, is based upon the most recent evidence Restoration by Charles R. Knight, copyright The Chicago Natural History Museum huge spikes, presumably intended to serve You will observe by these remains as a pointed reminder to any other dinosaur The creature had two sets of brains- One in his head (the usual place), that might venture closer than was con- The other at his spinal base. sidered proper by Mr. Stegosaurus. Thus he could reason 'A priori' Whether the plates along back served the As well as 'A posteriori.' as a really effective protection to the spinal No problem bothered him a bit column is a question which at this distant He made both head and tail of it. date cannot be very satisfactorily answered. "So wise was he, so wise and solemn, At least they were decorative. Each thought filled just a spinal column. This dinosaur is famous, among other If one brain found the pressure strong things, for the small size of his brain. In- It passed a few ideas along. If something slipped his forward mind deed, this was a peanut-headed reptile, if 'Twas rescued by the one behind. ever there was one,—an animal bigger than And if in error he was caught an elephant, with a brain about the size He had a saving afterthought. of a walnut. It is a remarkable fact that the As he thought twice before he spoke brain of Stegosaurus was actually 20 times He had no judgment to revoke. smaller than the enlargement of the spinal Thus he could think without congestion Upon both sides of every question. cord in the hip, which served to control Oh, gaze upon this model beast, the movements of the heavy hind limbs and Defunct ten million years at least." the powerful tail. Which has given rise to —Bert Leston Taylor the quaint, and somewhat fanciful story that this dinosaur had two sets of brains—an It wasn't quite as bad as all that, but at any rate idea charmingly perpetuated by the late Stegosaurus must have been pretty Bert Leston Taylor, a columnist on the Chi- much a walking automaton, without much cago Tribune. of what might be called original thought.

Ankylosauria THE DINOSAUR The Cretaceous armored dinosaurs were "Behold the mighty dinosaur, the ankylosaurs, somewhat less startling in Famous in prehistoric lore, Not only for his power and strength appearance than the stegosaurs but perhaps But for his intellectual length. somewhat more effectively protected. These

ORNATE ARMOR helped to protect Palaeoscincus (center foreground) from other dino- saurs of his time. To the left is Trachodon, to the right (middle distance) Corythosaurus and (farther away) Parasaurolophus. In the center background are two Struthiomimus Restoration by Charles R. Knight, copyright The Chicago Natural History Museum THE FIRST OF THE HORNED DINOSAURS, Protoceratops, from the Cretaceous of Mongolia. In this primitive member of the group the horns were as yet undeveloped

Restoration by Charles R. Knight, copyright The Chicago Natural History Museum

dinosaurs had a real armor plating, an over- ranged far and wide, the gigantic Tyran- lapping pavement of bony plates presum- nosaurus and his lesser relatives. By seeking ably covered with horny sheaths, which en- refuge within the strength of his shell he cased the entire body, head and tail, arma- was fairly safe from attack, and with the dillo-fashion. knout on the end of his tail he might lay Ankijlosaurus (an-kyle-o-SAWR-us) was about him, to create devastation within the typical of this group of dinosaurs. A me- arc swept by that mighty club. dium-size dinosaur this was, quadrupedal Most of the other armored dinosaurs of in pose and of heavy build. The skull was the Cretaceous were generally similar to broad and strongly protected by the armor Ankijlosaurus. Of these, Palaeoscincus plates, while the arched back was com- (pale-e-o-SKiNK-us) and Nodosaurus (node- pletely encased by the articulating scutes. o-sawr-us) may be mentioned.

Add to this a heavy, stiff tail, ending in a Ceratopsia huge clublike mass of bone and you have a picture of Ankijlosaurus. Of all the dinosaurs the Ceratopsia (ser- Here was the tank of Cretaceous days, a-TOPS-e-ya) or horned ornithischians were low, squat, and strongly protected by his the last to appear. The earliest ceratopsians outer casing. He could blunder along appear in beds of Cretaceous age, and in through the world without a great deal of the relatively short lapse of geologic time concern about the rapacious carnivores that between their rise and their final extinction

79 these animals enjoyed a remarkably varied form a pierced or fenestrated frill that over- course of evolutionary adaptation. hung the neck and the shoulder region. Like

The ancestry of the ceratopsians is indi- the other ornithischians, Protoceratops

cated, if not actually represented, by a small lacked teeth in the front of the jaws, except bipedal dinosaur from the Lower Cretace- for two tiny vestigial teeth on each side ous of Mongolia, known as Psittacosaurus near the front of the upper jaws—obviously

(sit-a-ko-SAWR-us). This little animal was an evolutionary "hang-over" from a more

characterized especially by the develop- primitive stage of development. This little

ment of its skull, which was very deep and animal, although a horned dinosaur, had

narrow, so that the front of it formed a large only the beginnings of a nasal horn, for he

pointed beak, similar to the beak so charac- was the first of his line and had not devel-

teristic of the horned dinosaurs. Indeed, oped the specializations that were so char- Psittacosaurus, as has been shown by Greg- acteristic of his large and impressive grand-

ory, is an almost ideal ancestor for the cera- children.

topsians, not only with regard to the devel- Protoceratops is known from a number opment of the skull but also because of the of skeletons and from a remarkable series of characteristic expression of the pelvis, in skulls which show the development of this which the pubic bone was reduced (a typi- animal from a newly hatched baby to a cal ceratopsian feature), and because of the fully developed adult. These skulls show,

form of the limbs and of the feet. A series for instance that the flat "frill" at the back running from Psittacosaurus to Protocer- of the skull was not present in the newly atops (prot-o-SER-at-ops) (the first of the born Protoceratops, but that it grew as the "frilled" ceratopsians), and to the later animal grew up, so that by the time adult- forms, shows how the small two-legged hood was attained, there was a well-devel-

dinosaurs became specialized to give rise to oped, fully-formed frill. Incidentally, it is

the giant horned dinosaurs of Upper Cre- probable that this frill grew as an accom- taceous times. modation for strong neck muscles which

The first of the frilled ceratopsians was controlled the movements of the head, these a small dinosaur known as Protoceratops, in turn being made necessary by the great discovered a few years ago in the upper relative increase in the size of the skull. Cretaceous Djadochta beds of Mongolia. To make our knowledge of Protoceratops

This little ornithischian was five or six feet really complete, there were discovered with

in length, and in spite of its comparatively this little dinosaur several nests of its eggs.

small size it would seem to have been al- These were the first dinosaur eggs to be most entirely quadrupedal. Evidently the discovered, and as such they became very four-footed pose was established at a very famous in the public press some years ago. early stage in this line of dinosaurian de- The eggs are similar in shape and in surface velopment. texture to the eggs of certain modern tur- The most striking feature of Pwtocera- tles. In two of them were found the bones

tops was its head, which was relatively very of an unhatched embryo Protoceratops! large and deep. The front of the muzzle and From the modest beginnings of Protocer- the jaws formed a hooked parrot-like beak, atops, the giant horned dinosaurs of late and the back of the skull extended back to Cretaceous times evolved. Of the great

80 *^J^J|t'

A.M.N.H. photograph A nest of eggs of Protoceratops, the ancestral horned dinosaur, as they were dis- covered in Mongolia by the Central Asiatic Expedition of the American Museum of Natural History

ceratopsians, Triceratops (try-SER-at-ops) is at the hips. Needless to say, Triceratops was typical and is perhaps the best known fully quadrupedal, with strong limbs, and genus. short, broad feet. The remarkable feature

This was an animal about 20 to 30 feet of Triceratops and of all the large horned in length, standing some eight feet in height dinosaurs was the enormous head, constitut-

The last of the horned dinosaurs: Triceratops, a strong animal, admirably equipped for defensive fighting. The eight-foot skull with its flaring "collar" was fully one- third the entire length of the animal. From the Upper Cretaceous of North America

Restoration by Charles R. Knight, copyright The Chicago Natural History Museum Restorations by John C. Cermann ADAPTATIONS IN THE HEAD OF THE HORNED DINOSAURS

MONOCLONES

From the ancestral type below

evolved the first of the "frilled"

ceratopsians, Pro focero fops. Evolution in the late horned dinosaurs, as shown above, was marked by varying adap-

PROTOCIRATOPS tations in the horns and frill

The probable ancestral type

is indicated by the small

genus psittacosaurus PSITTACOSAURUS ing fully one-third of the entire length of was eminently useful to Triceratops, for he the animal—an accentuation of a develop- lived in a land inhabited by Ti/rannosatirus, ment that was already apparent in Proto- than whom there never was in this world a ceratops. Thus, in a large Triceratops the more powerful adversary. skull was some eight feet in length, of The other giant ceratopsians of late Cre- which about one-half was occupied by the taceous days were variations on the Tricer- great flaring frill that extended back over atops theme. Their differences were ex- the neck and shoulders. As in all of the pressed mainly in the development of the other ceratopsians, the skull and jaws were horns and the frill. deepened and narrowed in front to form Thus there was Chasmosaurus (kas-mo- a hooked parrot-like beak. This animal car- sawr-us), with small horns. And Mono- ried on its nose a stout horn, and over the clonius (mon-o-KLON-e-us) with a large horn eyes were two other horns, these latter on the nose and small horns over the eyes. very long and strong and admirably suited And Styracosaurus (sty-rak-o-SAWR-us) with for defensive fighting. a large horn on the nose, no horns of conse-

The skull of Triceratops was attached to quence above the eyes, but spikes all the backbone by a ball-and-socket joint at around the margin of the frill. the back of the brain case, which was at These were the last of the dinosaurs. about the middle point of the skull, beneath They came onto the scene of dinosaurian the front of the frill, so that the skull was evolution during its final stages and disap- virtually balanced upon it. With tremen- peared, along with certain other final sur- dous neck muscles attached to the bottom vivors, during that great transition between of the frill, combined with strong leg mus- Mesozoic and Cenozoic times, when rep- cles, Triceratops must have had a remark- tilian dominance gradually yet unequivo- able ability for making short powerful cally gave way to mammalian dominance lunges with the head down and the two on the earth. Their history was relatively long horns directed forward to impale any short, but while it lasted it was varied, in- luckless antagonist. Such an arrangement teresting, and successful.

83 10

Adaptations of the Dinosaurs

3 ime flies, but the life of the world goes the characters as well as the pose of their on. Today fat cattle graze across the thecodont ancestors, while the large dino-

P western prairie where yesterday there saurs, such as the great bipedal carnivore, were bison. Today the white-faced steers are Tyrannosaurus, or the quadrupedal giant, rounded up by cowboys, to be shipped to Brontosanrus, showed many specializations market, where yesterday the bison was in form and in pose over their small trailed and hunted by the wolf. Life is a ancestors. continuous round and an unending struggle As has been pointed out on a preceding between the hunter and the hunted, it is a page, growing big isn't a simple matter of story of many kinds of plants and animals duplicating a small-scale animal on a large fitting into their various roles by means of scale. The large animal is confronted by adaptation to the environment. many problems of mechanics, of stresses

So it was in the days of the dinosaurs. and strains, which never bother the small Then as now there were the plant-eaters, animal. On the other hand, the large animal getting their livelihood direct from the is relieved to a certain extent of some prob- green products of Mother Earth. Then as lems, of heat loss for instance, that are im- now there were the hunters, feeding upon portant in the physiology of the small the inoffensive herbivores. There were the animal. large plant-eaters and the small plant-eaters, As the giant dinosaurs increased, there the large hunters and the small hunters. were many adaptations as a result of the There were the upland forms and the ani- stresses and strains placed upon bone, mals of the swamps, the rivers, and the muscle, and ligament consequent upon the lakes. There were the tree climbers and the ever-increasing bulk of these animals. diggers in the earth. All formed a part of Compare the giant Tyrannosaurus with the the ecology of the time—that complex rela- small Ornitholestes. Tyrannosaurus, al- tionship between the various forms of life, though a two-legged dinosaur like his the "balance of Nature" as we often call it, small cousin, lost the lightness and graceful- whereby each plant and each animal is ness of limb and foot that were so char- adjusted to the topography, the climate, acteristic of Ornitholestes. In Tyranno- and the life that surrounds it. saurus there were several tons of weight to The adaptations of the dinosaurs were be carried around, so that the legs became numerous, for in Mesozoic days these rep- very heavy and strong, while the feet tiles filled many of the "ecological niches" broadened to form a good support and to that are occupied by the mammals of our furnish traction against the ground. own time. In an upright animal of gigantic size, Some of the dinosaurs were large and such as Tyrannosaurus, the strain on the others were small, as we have already seen. hips—the fulcrum for the bodv—must have The small dinosaurs, such as the "bird been enormous. Thus, it can be seen that catcher," Ornitholestes, retained many of the connection between the hipbones and

84 Brontosaurus the backbone in this animal was strength- bridge, the backbone of ened by the lengthening of the sacrum, so stretched between the strong abutments that an additional vertebra became attached of the limbs and their girdles, and beyond, a to the upper hipbones, the ilia. Compare to form the neck and the tail. Here was this with the comparatively small attach- problem that required for its solution ment between the backbone and the hips in strength combined with lightness; strength little Ornitholestes. upon which to hang the many tons of body,

It is in the great sauropods, however, neck, and tail, lightness so that the vertebral that we see the most advanced adaptations column itself, necessarily large because of to large size. These huge dinosaurs, 70 or the needed strength, would not be over- 80 feet in length and weighing 20 or 30 or burdened by a great amount of "dead 40 tons, must have experienced problems weight" of bone. The problem was solved in mechanics that have never before or by the inexorable processes of evolution, since plagued a land-living animal. so that the vertebrae became "excavated"

So it is that the limbs in these dinosaurs where bone wasn't needed. In other words, were heavy and postlike and the individual bone was formed along the lines where bones were extraordinarily massive and stresses would come and it was taken away dense—veritable pillars for the support of from those areas where there were no par- the animal. Likewise, the feet of these giant ticular stresses, just as in the trusses of the sauropods were short and broad, so that steel bridge or in the flying buttresses of a they formed massive, round pediments Gothic church, strength is achieved without through which the weight of the body was a resort to massiveness. In addition, the thrust against the earth. spinal column in the sauropods was Like the lacy trusses of a cantilever strengthened by extra articulations between the vertebrae, which gave in effect addi- tional interlocking joints to strengthen the

backbone without decreasing its flexibility. STRENGTH AND LIGHTNESS simul- The dinosaurs lived in all kinds of sur- taneously achieved: a bone from the neck of roundings. Some of them were upland the giant sauropod dinosaur, Brontosaurus. fairly rapid progres- Note the concentration of bony material forms, well adapted to along lines of stress and the formation of hol- sion over hard ground. Such was the case lows in other portions with many of the bipedal theropods, the

From Osborn and Mook, 1921 small carnivores such as Ornitholestes and the large carnivores such as Allosaurus and Tyrannosaurus. Such was also the case with many of the quadrupedal types, par- ticularly the horned dinosaurs of Cre- taceous times and many of the armored dinosaurs. These upland forms were seemingly rather active—at least for reptiles. The bipedal animals were able to run or walk about with some show of speed, by virtue

85 Brachiosaurus of their swinging, two-legged stride. The mentioned on a previous page, we know quadrupedal forms, such as the horned that these dinosaurs had webbed feet, from

dinosaurs, were built as efficient walkers; the several "mummies" that have been pre- the limbs were strong and the belly was served. In addition, the trachodonts had

raised high off the ground. deep, narrow tails that must have aided Other dinosaurs were lowland animals, in swimming— tails that were curiously living in marshy country or along the shores strengthened and perhaps stiffened by calci-

of rivers and lakes. It would seem that fication of the tendons of the back muscles, these animals spent much of their time in to form a lattice-work binding the bones of the water, feeding among the lush marsh the spinal column. plants or even venturing out into deeper But the most striking features of the waters to escape from their traditional trachodonts were the developments of ac- enemies, the giant carnivores. cessory structures on the top of the skull Many of the lowland dinosaurs were in many forms, as already described and

probably slow and sluggish. It is likely that illustrated. These crests, in such animals as Brontosaurus and his relatives spent much Corythosaurus, Lambeosaurus, and Para- of their time moving along slowly, feeding saurolophus, were formed almost entirely upon green plants. Perhaps these giant by the bones surrounding the nostrils, the sauropods passed considerable time in mo- premaxillary and nasal bones, and to a tionless torpor, as do some of the large small extent by the frontal bones of the crocodiles in our own times. forehead. It would seem from dissections The aquatic habits of the sauropods are that have been made, that the crests in the attested to by the structure of the skull in hadrosaurs were occupied by the nasal some of them. In Diplodocus, for instance, passages which were thereby lengthened so the nostrils were placed on the top of the that they formed air storage chambers. The

head, as is so often the case in water-living usefulness of such an arrangement to an beasts, to facilitate breathing. This develop- aquatic animal that may have kept the head ment is accentuated in the gigantic submerged for considerable periods of time Brachiosaurus from Africa, in which the is obvious. nostrils were raised so as to protrude above It has even been suggested that certain the top line of the brain case. dinosaurs may have been tree-climbing The truly aquatic dinosaurs were, how- reptiles, living a life not unlike that of some ever, the trachodonts or hadrosaurians. As of our larger tree-climbing mammals of the present day. One form in particular, Hypsilophodon (hips-i-LOF-o-don), shows grasping feet that would seem to have been ^™ Brachiosaurus could breathe with only a small for clasping >ortion of the head above the surface of the water. The adapted branches. This was a lostrils were on an eminence on top of the head. Para- rather small dinosaur, and there is no aurolophus, a duck-billed dinosaur, had a greatly reason why it might not have lived in trees. elongated nasal passage within the crest. This presum- The ancestral thecodont reptiles were ibly formed an air storage chamber which enabled carnivorous, and the carnivorous diet was he animal to remain under water for a considerable seriod retained by most of the theropods. As might

)rawings by John C. Cermann be expected, the giant theropods, such as

87 Allosaurus and Tyrannosaurus, had widely to chop the food by a scissor-like motion gaping mouths armed with huge, bladelike of the jaws. teeth. Only in the toothless "ostrich dino- Modifications of these teeth occurred in saurs" such as Struthiomimus was there a the armored dinosaurs and in the cera- departure from this primitive or ancestral topsians or horned dinosaurs, but it was in carnivorous diet among the theropods. the aquatic hadrosaurs that the dental bat-

Most of the dinosaurs were, however, tery attained its most specialized form. herbivorous, living upon green plants. In There was in these dinosaurs a tremendous this category, we find the sauropods among increase in the number of the teeth so that the Saurischia and all of the dinosaurs instead of a relatively few teeth in each belonging to the order Ornithischia. Con- jaw, above and below, there were in each sequently there were various adaptations jaw some 500 teeth. Thus there was a total for eating plant food in these animals. of about 2000 teeth in the mouth of a In the giant sauropods dental adaptation typical duck-billed dinosaur. These teeth, seemed to be mainly a process of limiting which were small and rather lozenge- the teeth to the front of the jaws and trans- shaped, were arranged in several closely forming them into rather weak pegs. How packed rows. When worn, the overlapping such teeth, mounted in such small jaws, surfaces of the teeth formed a rough pave- could serve to tear off enough leaves from ment that served to grind the food, mill- their stems to keep these huge dinosaurs fashion, into a pulpy mass. As in a well- going, is a problem that baffles the imagina- organized army, there was a large number tion, yet the evidence is there and cannot be refuted. These dinosaurs did live, and very successfully too, for many millions of years.

In the ornithischians the teeth were re- stricted to the sides of the jaws, the front of the jaw being transformed into a sort of a beak, as mentioned above, consisting of the premaxillary bones in the upper jaw and of a new element, the predentary bone, in the lower jaw. This sharp, birdlike beak must have served these dinosaurs for the purpose of tearing green leaves away from their stems.

When it came to the process of chopping and chewing the plant food into digestible qp In the Saurischia, as illustrated by bits, the ornithischians were admirably Allosaurus, the hinge of the jaw is line with the provided with dental batteries of consider- approximately on a tooth sockets. The jaws were closed able complexity. In the primitive campto- by a scissors action, with the upper saurs there was a row of fluted teeth on and lower teeth sliding past each either side of each jaw, which when worn other maintained sharp edges that would serve

88 of "replacements," so that as the teeth in the teeth, so that the mouth was closed by use were worn they were pushed out, until a scissor-like action, whereby the sharp past they wore away completely, to be replaced teeth of the lower jaw were sheared car- by new teeth. It is a complex structure and those of the skull. In this manner, the a difficult process to describe, but the ad- nivorous theropods were able to tear and

vantage of such an arrangement is obvious. cut their unfortunate victims into sizable

Adaptations to diet were not only re- chunks that might be swallowed. flected in the structure of the teeth of the It is interesting to see that the giant dinosaurs, but also extended to the develop- carnivores had an expansion of the back ment and the articulation of the jaws. This part of the lower jaw, which afforded in- follows the principle that biting and chew- creased attachments for the powerful ing among the vertebrates are not alone muscles that activated the bite in these functions of the teeth, but are dependent fierce hunters. It is interesting to see, also, upon the structure of the skull, the strength that in the toothless, fruit-eating "ostrich of various muscles, and the movements of dinosaurs," such as Struthiomimus, the the jaws. typical theropod method of jaw articulation In the Saurischia the jaws worked on was retained, even though these animals what might be called the "scissor principle." had departed from the ancestral car- This may be explained by saying that the nivorous diet. articulation or fulcrum for the jaws was What about the great sauropods? Here on a line with the edges of the jaws and again, the primitive "scissor" articulation of the jaws was retained, even though these huge dinosaurs had turned entirely to a UTING IN vegetarian diet. The heritage of the an- DINOSAURS cestor was retained in the descendant. The reason for this lack of specialization

in the jaws of the sauropods is probably to be found in the fact that these great dinosaurs seemed to have indulged in very

little if any chewing of their food. They simply cropped the plants that came within reach of their small front teeth and then

swallowed whole the green stuff, to be worked on by the gastric juices of the

digestive tract. In the more highly developed Orni- thischia departure the rnithhchut, as illustrated by there was a from Trachodon, the hinge of the jaw is below generalized form and articulation of the the line of the tooth sockets, and the jaws saurischian jaws. The Ornithischia, as we action, with are closed by a "nutcracker" know, were herbivorous, and it would seem the teeth clamping together almost all at that they were able to cut and chop and the same time Drawing* by John C. Germans in some cases even to grind their food between their lateral dental batteries. Con-

89 sequently, in these dinosaurs the jaw In the carnivorous theropods the teeth

articulation was depressed so that it was constituted the principal means of defense. placed on a level much lower than that Needless to say, "defense" in these animals of the teeth. An analysis of the movements was mainly of the offensive variety; they of the jaws in these animals will show that were able to survive because of their

this articulation served to bring all of the pugnacity.

upper and lower teeth into contact at about It is quite possible that these dinosaurs the same time, in what might be called a also used the hind feet in fighting, and that "nut-cracker" or crushing action. This they were able to claw and scratch with

method of chewing is an obvious advantage their hooklike hands.

to a plant-eating animal, particularly if the Many of the dinosaurs sought safety in

animal indulges at all in the pleasure of flight. This was true of the smaller

grinding its food. theropods such as Ornitholestes and The dinosaurs developed many bodily Struthiomimus, and in some of the weapons for "defense," whether such de- Ornithischia, notably the duck-bills. In the

fense was of the passive variety, or of the case of the trachodonts, it is likely that more active and vigorous method of de- running away was directional—in other fense by offense and counter-offense. For words, that these animals would make for the world of the dinosaurs was one of the water as soon as one of the great car-

unending strife, of a constant struggle be- nivores came over the horizon. So with tween those that would eat and those that them there would be a dash for the shore, would rather not be eaten. a great deal of splashing about in the

y A reconstruction of the head of Pachy- cephalosaurus. Note the ornate nobs A.M.N.H. photograph

^ The champion bonehead, Pachycephalo- saurus, whose name means "the thick-headed reptile." All of the space above the brain is occupied by solid, dense bone

90 shallows, with water flying up in a high spray, and finally a quiet escape through the friendly deep waters. Many of the ornithischian dinosaurs were armored in one way or another. In the true "armored dinosaurs," the stegosaurs and ankylosaurs, there were protecting plates and spikes, which reached the climax of their development in such animals as Ankylosaurus and Nodosaurus. These dino- saurs were the armadillos of their day.

When danger threatened, it was necessary only to curl up, or possibly to flatten out against the ground and let the attack rage past. These animals were not, however, merely passive defenders of their rights.

Almost all of them had spikes or clubs on the end of the tail, lethal weapons of great value in beating off an attack. Some of the ornithischian dinosaurs, the troodonts, were remarkable in the protec- tion given to the brain by the skull. In these animals the skull roof became enormously massive, not through the development of

sinus cavities as is usual in the vertebrates, but by the actual thickening of the bones. In one of these animals, for instance, there was a protection of some ten inches of solid, dense bone above the brain, although why such a lowly brain should need such vault-

like protection is something to wonder about.

The horned dinosaurs, it would seem, in- dulged in "active defense." These were the "rhinoceroses" of their day, blundering

across upland glades and challenging all potential enemies by the power of their

^ An earlier form of the boneheaded dinosaurs, Troodon, an animal only about six feet long but already showing promise of a bonehead to brag about

Drawing by John C. Germann

91 strong bodies and the length of their horns. round was largelv a series of reflex actions, Triceratops might face his adversary with of responses to external stimuli. They lowered head, the long horns pointing for- muddled through life in a ponderous ward to impale his foe, the huge frill, to world. which were attached the powerful neck Not only was the brain of the dinosaurs muscles, flaring up behind as a protection of lowly form, but it was extraordinarily for his neck and back. With a short rush small, when one considers what huge ani- his attack was one of great power. He mals these reptiles were. It is a well-known needed it, in a world where Tyrannosaurus fact, established many years ago, that large was running rampant. animals have smaller brains in comparison Finally, some of the dinosaurs were pro- to their size than do small animals. For tected, or at least partially protected, by instance, an elephant weighing six tons has their great size. These were the giant sauro- a brain weighing about ten pounds, which

pods. They were so large that only the is approximately 1/10 of one per cent of largest of contemporary carnivores even the body weight. Compare the latter dared to attack them. Perhaps at that the figures with those for a sheep, in which the

carnivores were forced to limit their dep- body weight is about 75 pounds and the redations to such of the giants as might brain weight about three and a half ounces, be injured, or bogged down, or possibly to in a ratio of 3/10 of one per cent of brain

the little sauropods. to body weight. Or compare the body It must always be kept in mind that the weight of about seventeen pounds to a dinosaurs were reptiles. Being reptiles, brain weight of two and a half ounces in a

their life was less well organized and less fox-terrier dog, which gives a ratio of well directed than are the activities of the brain to body weight of almost 9/10 of one

mammals so familiar to most of us. It is per cent. From the above figures it is certain that the dinosaurs had a reptilian readily seen that the brain of the elephant

brain of comparatively lowly form and is much bigger than that of the sheep or organization, so these were not what we the dog even though in relation to body

would call "thinking animals." Their daily weight it is smaller. Giantism in the ele-

The brain of Stegosaurus was only one-twentieth the size of an enlargement in the spinal cord in the hip, which served to control the movements of the hind limbs and tail Drawing by John C. Gernann

_ Sacral Enlargement ^L.nlargement

1 Brain The great size of dinosaurs may have been caused by enlargement of the pitui- tary gland. This illustration shows the relatively large size of the pituitary body in relation to the primitive brain of a troodont dinosaur

Drawing by John C. Germann

phant's body has been accompanied by a vertebrates this pituitary body is relatively certain degree of giantism in the brain, but small. In the dinosaurs it was relatively in the dinosaurs not only was the relative large, and it is an interesting fact that in size of the brain small, its actual size was the huge sauropods it was very large. There also very small. Thus in Stegosaurus, an was evidently a correlation between the animal as heavy as a modern elephant, the enlargement of the pituitary body and the brain was no larger than that of a small size of dinosaurs. kitten. The functions of the pituitary body in Indeed the diameter of the brain in the recent vertebrates are various, but among large dinosaurs was in many cases less than other things the anterior lobes of this gland, that of the spinal cord, while in size it was the very part of the pituitary body which much smaller than the brachial and sacral seemingly was enlarged in the dinosaurs, enlargements of the cord in the shoulders secretes the growth hormone. This means and hips which served to control the move- that animals with large, active pituitaries, ments of the legs and tail. For instance, in are large animals. So it is not surprising to Stegosaurus, as already mentioned, the see that in those dinosaurs which showed sacral enlargement was 20 times as large an excessive enlargement of the pituitary, as the brain. As a matter of fact, the dino- the individual reached gigantic propor- saur brain was probably, in the main, a tions. receptor mechanism—a center where the Of course giantism in the dinosaurs was visual images, the odors, and the sounds closely related to the environment. Those coming in from the outside world were dinosaurs with active growth hormone se- received so that the animal's activity might cretions and enlarged pituitaries became be correlated with the environmental con- dominant because the climatic and other ditions indicated by these outside stimuli. environmental conditions of later Mesozoic

One interesting development in the dino- times were favorable to giantism. It is all a saurs was the great enlargement of the part of a correlated and complex picture, pituitary body attached to the base of the the whole of which must always be kept brain. In all but the "giants" among recent in mind.

93 11 Dinosaurian Associations

have had a glimpse at the va- found in the Morrison formation of Wyo- FEriety of dinosaurian evolution. ming, Colorado, and certain other western We have seen how these domi- states. These dinosaurs are found together, nant reptiles of the Mesozoic land became and under such conditions of deposition

adapted to numerous environments and to that there can be no doubt that they all

different modes of life. All of this has given lived at the same time. us a fairly comprehensive view of the dino- In the dim and distant days of the saurs as zoological units—as living mecha- Jurassic the West was not a land of high nisms that have become modified in various mountains and broad prairies, a land of

fashions, while at the same time they have clear blue air, as it now is. Indeed, quite

maintained certain basic relationships to the reverse conditions prevailed. It was a one another as members of two great rep- land of low-lying tropical swamps, of tilian orders having a common ancestry. steamy jungles and marshes where the sun

Yet the picture is not complete, because filtered through dense, monotonously green

little attention has as yet been given to the foliage—palms and ferns and water-plants. "ecological relationships" of the dinosaurs, Here lived the Morrison dinosaurs, an to those complex interrelationships that are integrated association of animals, the small present in any community of animals. Let and the large, the hunted and the hunters. us look at the dinosaurs as they dwelt to- There was a pattern of life, just as there is gether, let us see in the mind's eye how today on the western plain, but it was a they lived and fought and died. pattern on a giant scale. The dinosaurs, as has been said—perhaps Darting back and forth through the to the point of monotony—persisted over a dense undergrowth was Ornitholestes, the period of great geological length. They little carnivore, the one dinosaur of the lived in all quarters of the globe. Obviously Jurassic that retained to a considerable de- it is impossible to attempt in a few brief gree the structure and the habits of its paragraphs to describe all of the dinosaurs distant Triassic ancestors. Ornitholestes of the Mesozoic on all of the continents. was certainly one of the less conspicuous

Nor is such a procedure necessary. The members of the Jurassic fauna, a small ani- dinosaurs conformed to certain well- mal stalking small prey. established types, characteristic of each of There was nothing shy about Allosaurus, the Mesozoic periods. A fairly adequate the tyrant of the Jurassic scene. Here was picture of the more specialized dinosaurian a carnivore of gigantic size, stalking across assemblages may be had by picking out one the dry ground between swamps and lakes, dinosaurian association from the Jurassic hunting giant prey with nothing to fear but period and another from the Cretaceous. other members of his own species. Of all the Jurassic dinosaur faunas, none Dominating the scene in bulk, but not is better known nor more characteristic than in spirit, were the giant vegetarians the so-called Morrison fauna—the dinosaurs Brontosaurus and Diplodocus. Theirs was

94 a generally peaceful life, a life lived in the which lived in North America in late

swamps and marshes, where they fed on the Cretaceous times and which is found in leaves of lush plants, waded shoulder deep the Belly River formation, now exposed through small lakes, lay for hours in rep- in certain portions of southern Alberta. tilian torpor, engulfed by the damp warmth At that stage in the history of the earth of the jungle. There were occasional punc- conditions were quite different from what

tuations to this quiet life, intervals of they had been in Jurassic times. North

wild alarums, of attacks by Allosaurus and America was still a country having a warm,

his kin, of escape to the deep protective equable climate, but it wasn't the low-lying

waters of the lakes or to the soft, impassable tropical region that it had been when

mire of the swamps where the giants were Brontosaurus and Allosaurus were alive. It safe, where they might resume their slow, was now more of a semi-tropical region, ponderous round of daily inactivity. with palms and ferns along the shores of Then there was Stegosaurus, the armored the rivers, inland seas, and lakes, but with

dinosaur, living in the uplands, if the high upland regions of some height forested ground between the swamps and marshes with such familiar trees as oaks and willows, may be called uplands, feeding upon green sassafras and hickory. This was the environ- plants, protecting himself from the attacks ment in which the late Cretaceous dino- of Allosaurus by a "hedgehog defense," by saurs lived. a passive presentation to the attacker of Of these later dinosaurs Struthio7nimus, thick hide and plates, and cruel spikes on the so-called ostrich dinosaur, played one

the end of a viciously swinging tail. This of the lesser roles in the drama of life. Here much can be said for Stegosaurus, at least was a relatively small and inoffensive ani- he met aggressive attack with a certain de- mal, occupying much the same position in gree of aggressive defense, and thus he was the Cretaceous scene that Camptosaurus able to survive in a harsh world. had in the Jurassic landscape. Struthiomi- Finally, among the Morrison dinosaurs mus lived on succulent plants and perhaps there was Camptosaurus, one of the two- upon such small animal fry as he might be legged ornithopods, a rather small and in- able to catch. He was long of hind limb and offensive plant-eating animal. Campto- slender of build—obviously designed to saurus was perhaps too large to dart into vanish with great speed the moment any the undergrowth as did Ornitholestes, but of the ever-dangerous carnivores might

it is probable that this little dinosaur had appear over the horizon. to make himself relatively inconspicuous or Of the carnivores, Gorgosaurus was

even scarce on occasions if he were to sur- typical. This was a larger and more active vive. At this Camptosaurus was eminently cousin of the Jurassic Allosaurus, and an successful, for he and his descendants sur- animal that was specialized to prey upon vived into the following geologic period, the various large herbivorous dinosaurs that

which is more than can be said for some of inhabited the Cretaceous landscape. It was the other Jurassic dinosaurs. an advanced member of the line of car- Such was life in the Jurassic. nivorous dinosaurs, a line which culminated Let us now go forward from the Jurassic with the gigantic Tyrannosaurus, of upper- to catch a glimpse of the Cretaceous dino- most Cretaceous age. saurs. This time we will choose the fauna Of the large herbivorous dinosaurs,

95 there was a great variety of forms. Along and Styracosaurus were the Belly River the rivers and lake shores were the semi- representatives. These powerful animals, aquatic duck-bilk, Trachodon and his with their efficient nose horns, were seem- crested cousins, Corythosaurus and Para- ingly quite capable of repulsing the attacks saurolophus. These animals fed upon the of the carnivores under ordinary conditions. water-plants of the bank or of the strand, Such was the pattern of life in Cretaceous and perhaps upon certain mollusks, too. times, one that repeated the pattern of the They were water-lovers and even when on Jurassic scene but with the use of different land were ready to dash into the protection elements, a pattern that is repeated even of their aquatic environment at an instant's today on a less grandiose but perhaps on a notice. Needless to say, such notice was more efficient scale among our mammals. usually the sudden appearance of Gorgo- If we can visualize this pattern, a melange sourus or one of his predatory relatives. of interrelated animals running through Inhabiting the uplands were the armored geologic time, we will be that much better and the horned dinosaurs, plant-eaters that able to appreciate the structural modifica- were well equipped to beat off or with- tions which in the dinosaurs attained such stand the attacks of the fierce carnivores. a variety of forms. Let us therefore remem-

Palaeoscincus was a typical armored form, ber the pattern as it has been pictured here, a veritable dinosaurian tank, or armadillo, a pattern of hunter and hunted, of carnivore completely encased by heavy armor plate, and herbivore, of large and small, of upland with a spiked tail capable of wreaking and aquatic, all living together and adjust- havoc on anything that came within reach ing themselves to each other. That is the of its powerful sweep. key to the adaptive radiation of the Of the horned dinosaurs, Monoclonius dinosaurs.

96 12 Flight

n Jurassic times there occurred a new the Cretaceous-Cenozoic transition, to in- and a very important event in the long habit the air of our present-day world. j

and complex history of the verte- It would seem almost as if the "time was brates. This was the development of the ripe" in Jurassic days for the appearance of power of flight. flying vertebrates. Perhaps a more accurate The story of the backboned animals explanation would be to say that in the throughout their pre-Jurassic history was Jurassic period of Earth History the verte- one of animals living in the waters, or brates had attained a complexity and per- venturing out of this ancestral habitat to fection of bodily makeup that made it try their fortunes on the solid land. During possible for them to overcome, through a stretch of geologic time of great im- evolutionary processes, the severe difficul- mensity, a period measured by the hun- ties of flying. dreds of millions of years, the vertebrates We know from our own acquaintance were restricted to the waters and to the with the history of the airplane that flight lands, where, as we have already seen, they is no simple matter. It was attained by man developed an astonishing variety of forms, only after the invention of the internal com- adapted to numerous environments and bustion engine, when there was a combina- methods of life. But it was not until the tion of power and lightness sufficient to lift advent of Jurassic days, when tropical the man-made wings off the ground. This forests steamed beneath the sun and hordes evolution of the modern airplane offers an of dinosaurs ruled the land, that the verte- analogy with the evolution of the flying brates first ventured into the thin air, to vertebrates. Any backboned animal that soar upon outstretched wings, free from the attempts flight must: trammels of an earth-bound or of an a. aquatic existence. Transform the normal type of front limbs Strangely enough, two groups of animals into wings, took to the air in Jurassic times, and b. strangely enough, both of these groups Become light in the body while retaining a were closely related to the dinosaurs. One very strong skeleton and powerful muscles, group was that of the flying reptiles, the c. pterosaurs, which arose in the Jurassic, Have a highly developed nervous system, reached the culmination of their evolution- with a particularly fine sense of balance. ary development in Cretaceous times, and Let us see how the two groups of animals then became extinct along with their dino- which first attempted to fly in Jurassic times saurian cousins, during the profound transi- solved these problems. tion between Cretaceous and Cenozoic times. The other group was that of the PtsrosGuria birds, which likewise arose during the The pterosaurs (TER-o-sawrs) were Jurassic, but which successfully weathered diapsid reptiles of basic thecodont ancestry

97 They were lightly built, with hollow bones were strongly anchored to the backbone. which were strong yet at the same time Indeed, there was a new and special at- remarkably light. In the skull there was an tachment, not found in any other animal, unusual amount of fusion of the bones, that held the shoulder girdle firmly to the while the back was very short and strong, backbone, thereby affording a secure an adaptation brought about by a reduction anchorage for the long wings. Moreover, of the number of bones making up the the breastbone or sternum, attached to the spinal column. The pectoral and pelvic lower ends of the pectoral girdle and the girdles to which the limbs are attached ribs, was greatly enlarged to provide a

FLYING REPTILES. In the Jurassic form, Rhamphorhynchus, there were teeth in the jaws, and a long tail. In the advanced Cretaceous form, Pteranodon, the teeth had been lost and the tail reduced Restorations by John C. Germann

CRETACEOUS

TlWB^jr'^ir ** >||^

• - -

98 strong attachment for the strong breast habits of the pterosaurs, it is certain that muscles that moved the wings. In these these animals had a less efficient wing than highly modified reptiles the fourth finger of do either the birds or the bats. In the ptero- the hand was greatly elongated, and this saurs there was a single series of bones, the formed the support for a long, membranous fourth finger, running along the front edge

wing. The remaining fingers were small, of the wing as a support. Consequently, if hooklike claws, which evidently were used the wing membrane should be torn, these for hanging onto rocks or limbs. The hind animals must have found flying difficult.

limbs were very weak, so it would seem that Compare this with the several fingers that these flying reptiles were very poor walkers support the membrane in the bat's wing,

—in fact, it is doubtful whether they moved or with the feathers than constitute the around on the level ground to any extent at wing of the bird. The advantages of wing all. construction in these modern flying verte- The flying reptiles of the Jurassic period brates are obvious. (155 to 120 million years ago) were for the The brain in the pterosaurs was very most part rather small, often no larger than large, considering that it was a reptilian sparrows or robins. They were charac- brain, and it showed a strongly developed terized by the presence of teeth in the skull sense of sight and a weakly developed sense and lower jaw, and usually although not of smell. In these respects the pterosaurs always by a long, rudder-like tail. The were similar to our present-day birds; they Cretaceous pterosaurs (120 to 60 million soared aloft in search of their food, scan- years ago) were the giants among nature's ning the landscape and guiding their flight "flying machines." Pteranodon (ter-AN-o- through large and efficient eyes. don), for instance, had a maximum wing- Finally, it is barely possible that the spread of some 27 feet! These large ptero- pterosaurs were warm-blooded, at least par- saurs were specialized beyond their Juras- tially so. This is a "scientific guess" but it is sic forebears in that they had lost the teeth based upon the fact that these were spe- and the tail had become very short. cialized flying vertebrates and as such must What were the habits of the pterosaurs? have had to sustain action over considerable

These were quite obviously aerial reptiles, periods of time. Such a feat is difficult, if but it is doubtful whether they flew as not impossible, for the cold-blooded rep- much as they glided, or soared. These ani- tiles as we know them, but it would have mals were lightly built—even the giant been feasible should these ancient reptiles form, Pteranodon, with a wing-spread of have independently attained a warm- more than 20 feet, had a relatively small blooded condition, similar to that of the body—and it would seem probable that they birds or the mammals. were living gliders, majestically soaring Such was this first pattern for vertebrate back and forth on the warm currents of air flight—a pattern that was established in rising from the tropical landscape beneath Jurassic times and persisted to the end of them. Certainly they had a less powerful the Cretaceous. Even though it failed to and efficient muscular system for moving survive, just as so many other reptilian de- the wings than do our modern flying birds. velopmental patterns failed to survive the

Whatever may have been the flying Cretaceous-Cenozoic transition, it was

99 nonetheless successful, for it continued WING OF PTEROSAUR, BIRD, AND BAT over a period of some 50 to 60 millions of years. But it wasn't so successful a pattern for flight as was that of the birds, or of the

In the flying reptile, the wing bats. was a membrane supported by the elongated fourth finger. The The Birds other fingers were hooks by which the animal could hang from rocks Birds are little more than "glorified rep- or limbs tiles." True enough, to the average spectator there seems to be nothing in common be- tween the gorgeous blue and white flash of the jay, screaming his indignation

through the high branches of the oak tree, and the silent and sinuous menace of the blacksnake gliding through the grass, the object of the bird's imprecations. But under- neath the feathers of the bird and the shin- ing scales of the reptile the resemblances are there, and when the ancestries of these two apparently so dissimilar vertebrates are

traced back through the fossil record the

resemblances become all the more signifi- cant—the bird becomes ever more reptilian,

so that there can be little doubt as to its earliest orgin.

The birds, although classified as a

In the birds, the fingers are separate class of the vertebrates, are essen- coalesced. The wing surface is tially of basic thecodont ancestry. They are formed of the stiff primary feathers, which are attached to lightly built, with strong, hollow bones. the skin covering the lower part Not only are the bones extraordinarily of the arm pneumatic, for the sake of lightness, but also there are a number of air sacs in the body of the bird, which further contributes to its flying ability. The skull shows an un-

usual amount of fusion of the bones (just as was the case in the pterosaurs). The back

is short and strong, while the neck is rather

In the bat, the wing surface is long. The pectoral and pelvic girdles are

a membrane, but it is supported very strong; the latter is firmly attached to by several elongated fingers the spinal column by a greatly lengthened and strengthened series of articulations be- Drawings by John C. Germann tween the vertebrae and the sacral portion of the pelvis. In the typical flying birds the 100 breastbone has become greatly enlarged to more efficient than the pterosaurian wing, afford anchorage for the powerful pectoral a mechanism that allows the wing to muscles that activate the wings. In the large function even while replacements of ground-living birds such as the ostrich, no feathers are being made. Since the birds such development of the breastbone is seen, depend upon the long wing feathers for the but there is reason to think that in these flying surfaces, the finger bones have cases there has been a secondary reduction coalesced and become strengthened, to of this element from a formerly large struc- form a strong base of attachment for these ture. Thus far in this summary of the char- feathers. acteristics of the birds we see a considerable Again, the birds may be contrasted with amount of parallelism with the flying rep- the pterosaurs in the development of their tiles. This is as might be expected. We have hind limbs. It will be remembered that in been looking at adaptations imposed by the the pterosaurs the hind limbs were extraor- rigorous restrictions inherent in flying, dinarily weak, whereas in the birds the legs namely lightness and strength in the skele- are very strong—not unlike the legs in some ton, and provision for the attachment of of the two-legged dinosaurs. (In fact, the powerful muscles* to move the wings. similarity of the hind limbs in the birds and In certain ways, however, the birds have the dinosaurs affords one line of evidence followed a line of development quite differ- pointing to a certain degree of relationship ent from that of the pterosaurs. between these different types of vertebrates

In the first place, the birds have feathers, —a relationship dependent upon their de- and they have had them since they first scent from a common thecodont ancestry.) arose as but partially modified reptiles in Thus the bird is an efficient animal on the the Jurassic period. It is true that the ground, which the pterosaur most decidedly feathers are nothing more nor less than was not, and this may account in part for highly modified scales, but they are none- the survival of the birds and the disappear- theless important and basic in this differ- ance of the flying reptiles. entiation of bird from reptile. They afford In the bird brain, as in the pterosaur insulation for the bird, which is a warm- brain, there is a pronounced dominance of blooded animal. Compare this condition the visual areas, for the birds depend with the naked pterosaurs, which might chiefly upon sight for the direction of their have been warm-blooded, but at best movements. The sense of smell is greatly could have had this character only im- reduced. The part of the brain concerned perfectly developed. What is more im- with balance, the cerebellum, is very large portant, the feathers provide the flying in the birds, a development that is not sur- surfaces for the bird. Instead of having prising in an animal adapted for rapid and to depend upon a membranous wing, skillful flight. stretched upon an elongated finger or fin- It might also be mentioned that the birds gers, the birds have the wing surfaces have a high, constant body temperature, composed of the long, stiff, hard feathers, which enables them to sustain their activi- attached to the skin that covers the fingers ties over considerable periods of time. and the lower arm bones. (See illustra- Finally, the birds show a development tion.) Here is a mechanism ever so much which can only be guessed at so far as the

101 J flying reptiles are concerned. This is the tail, but a tail with feathers arranged on

remarkable perfection of nesting and the either side of it.

care of the young. Here is an adaptation It is probable that this first stage in the which in itself must have been of great im- evolution of the birds was a gliding stage, portance during past geologic ages in the a stage at which true flight had not as yet continuation of the species—an adaptation been attained.

which is completely lacking or at best only However that may be, it is certain that rudimentary in the reptiles that have sur- by Cretaceous times the birds had become vived into our present-day world. pretty good birds. These Cretaceous birds,

The earliest known bird is the famous which may be regarded as representing the Archaeopteryx (ar-kee-op-ter-ix), found in second stage in the evolution of the group, the Solenhofen limestones of Jurassic age, were for the most part about as well devel- in Bavaria. Of this form, two fairly com- oped along the lines of avian specialization plete specimens are known, one in the as are'the modern birds, except that teeth

Berlin Museum, the other in the British were still retained in the jaws. Conse-

Museum. quently they must be regarded as a link- Had this early bird not been found with between the very ancient and imperfect

the imprints of its feathers preserved, it is birds of the Jurassic period and the mod-

doubtful whether it would now be classi- ernized birds of Cenozoic and recent days. fied as a bird. For Archaeopteryx was in- One of the well-known Cretaceous birds

deed very close to its reptilian forebears. It was Hesperornis (hes-per-ORN-is), a swim- was beginning to show the coalescence of ming and diving toothed bird, evidently skull elements and the obliteration, so with habits similar to those of our mod- characteristic of the birds, of the temporal ern loon. In this bird the wings were openings behind the eye. Yet these develop- lost—the result of a secondary return to a ments had not proceeded to such a point non-flying mode of life. that the skull was really "un-reptilian" in Finally, with the opening of Cenozoic appearance. Moreover, there were teeth in times, birds became completely modern- the upper and lower jaws of Archaeopteryx, ized. The teeth were lost and the mouth teeth that were an heritage from reptilian became a horny beak, adapted to pecking grandparents. and biting.

The fore limbs were wings in Archaeop- In early Cenozoic times there was a con- teryx, but there was none of the perfection siderable development of large, flightless of adaptation seen in the later birds, for the birds, similar in habits to the modern fingers were long and not coalesced, while ostriches, rheas, and the like. At that stage the breastbone showed none of the expan- of Earth History, the mammals were still in sion that developed in the powerful fly- the earlier phases of their development, and ing vertebrates of later times. Moreover, the it would seem likely that these early flight- pelvis was only beginning to show the less bird giants were for a time serious developments that became so characteristic competitors with some of the mammals for of the birds, namely the fusion of bones to dominance of the ground. An exceptionally make it an extremely strong and rigid struc- fine example of one of these early flightless ture. And there was a long, reptilian-like birds was the large form, Diatryma (dye-a-

102 TRY-ma), from the Eocene of Wyoming. the harsh struggle ever present among the At this same time, however, the birds animals of the ground, that the birds were were developing as tree-living, flying crea- to find the environment best suited to the

tures, and it was to be in the air, free from establishment of their final dominance.

^m** CRETACEOUS

GERHArtri-

Restorations by John C. Gennann Four stages in the evolution of birds. The the Eocene period, giant ground birds such as primitive bird, Archaeopteryx, had feathers Diatryma may have competed seriously with and was probably able to fly, but in many the early mammals for dominance on the details it was essentially reptilian. The Cre- land. The modern birds are adapted for life taceous aquatic bird, Hesperornis, was com- in the treetops, on the ground, or in the water. pletely avian in structure, although it still re- (The tree depicted remained essentially the tained the teeth of its reptilian forebears. In same) 103 13 Sea Serpents

lthough the dinosaurs were the firmly tied by the bonds of their heritage. /\ undisputed rulers of the land in True dominance in the waters of Mesozoic Mesozoic times, they never ex- times was held by reptiles other than the tended their sway to dominance of the dinosaurs. These belonged to four groups: water. True enough, some dinosaurs were the ichthyosaurs, plesiosaurs, mosasaurs,

partially aquatic. The great sauropods spent and marine crocodiles. The first two of much of their time in the muck and water these groups belonged to the reptilian sub- of swamps and small lakes, while the hadro- classes Parapsida and Euryapsida, respec- saurs (the duck-billed dinosaurs) were ob- tively, containing those reptiles having a viously rather active swimmers. Yet even single upper opening in the skull behind these most aquatic dinosaurs showed only the eye, groups which we have not yet partial adaptations to a life in the bounding discussed. The other two groups, the mosa- waves. They were primarily land animals saurs and the marine crocodiles, of much that spent their days along the shores of riv- less importance as aquatic or marine rep- ers or lakes, wading about in the shallows, tiles, were related to the dinosaurs—either escaping to the deeper waters when danger distantly, in the case of the mosasaurs, or threatened, but always coming back to the by a fairly strong bond, as in the case of land—the environment to which they were the marine crocodiles.

An early aquatic reptile, Mesosaurus

The fishlike ichthyosaur, a perfectly streamlined and thoroughly aquatic reptile. Its ancestry can be traced back through a form possibly similar to Mesosaurus, to a typical land-living primitive cotylosaur like Seymouria

Drawings by Margaret M. Colbert

104 The Ichthyosaurs certain primitive cotylosaurians abandoned the land life which their labyrinthodont The subclass Parapsida consisted es- ancestors had so slowly and with such a sentially of two reptilian orders, the great struggle attained, and returned to the

Mesosauria (mes-o-SAWR-e-ya) and the Ich- primal environment of all life—the water. thyosauria (ik-thee-o-SAWR-e-ya). These two Thus arose the mesosaurs. orders of reptiles are often designated Whether the mesosaurs were the an-

collectively as the Ichthyopterygia (ik-thee- cestors of the ichthyosaurs is a moot point. op-ter-ij-e-ya). If they were not the actual ancestors, they The Mesosauria were late Carboniferous certainly paralleled the Mesozoic ichthyo- reptiles of aquatic habits, whose fossils have saurs, and for the purposes of reconstruct- been found in South Africa and in Brazil. ing a picture of the evolution of the They were rather small reptiles, usually Ichthyopterygia they serve very well as a less than two feet in length, and were long stage intermediate between the typical land- of head and body. The length of the skull living cotylosaurs and the typical aquatic

in these little reptiles, of which Mesosaurus ichthyosaurs.

is typical, was due in large part to the draw- The first ichthyosaurs, the fishlike rep-

ing out of the jaws in front of the eyes. tiles, appeared in Triassic times, and even These elongated jaws were armed with a at that early state in their evolutionary his- fearsome array of sharp teeth, and the tory they were fully aquatic reptiles. They combination of long jaws and pointed teeth reached the culmination of their develop- suggests the probability that this was a ment in the Jurassic and Cretaceous peri- fish-catching animal. There was a tapering, ods, only to become extinct at the end of

flexible tail, which was evidently deep and the Cretaceous, like so many of their

narrow—the type of a tail that one might Mesozoic contemporaries. expect to find in a swimming animal. More- These were reptiles of medium size and

over, the limbs were modified to form of fishlike form, a fact that is well estab-

paddles, of which the front pair was some- lished thanks to the fine sediments in which

what smaller than the hind pair. Thus it oftentimes not only the bones but also the would seem that Mesosaurus lived in the contours of the body are preserved. Con-

water, and it is indeed doubtful whether sequently we know that the ichthyosaurs, this little reptile ever ventured onto the like the fast-swimming fishes and porpoises land. of modern times, were thoroughly stream-

In spite of their adaptations to life in the lined. The body was thickest in its forward water, there are certain things about the part and tapered gracefully to the rear, Mesosauria that point to their descent from torpedo fashion. There was a large, two-

thoroughly terrestrial reptiles. For instance, lobed tail at the back of the body which the form of the vertebrae in these little acted as a scull, driving the animal through reptiles indicates quite clearly their deriva- the water. The four limbs were modified to

tion from cotylosaurian ancestors, from ani- form fins, and these undoubtedly performed

mals similar to Seymouria. Therefore it the same functions as do the paired fins in seems probable that at a very early stage fishes and porpoises, helping to maintain the

in the history of the land vertebrates, balance of the animal and aiding it in

105 Restoration by Charles K. Knight

Ichthyosaur with its young 106 turning and stopping. A stabilizer was pres- of the front of the body, a cutwater or prow

ent in the form of a large, fleshy dorsal fin, that served as the "entering wedge" for an

quite similar to the fin on the back of animal moving through a dense medium.

modern sharks and some porpoises. This fin The advantage of an immobile, short neck

kept the animal from rolling from side to in a fast-swimming animal is obvious.

side as it swam. The body was flexible, for these animals So much for outward appearance. In the must have propelled themselves in the same

ichthyosaurs the skull was elongated, with fashion as do fish, by a side-to-side flexion the jaws pulled out to form a pointed beak of the body, ending with a final push by the

or rostrum. These long jaws were armed tail. Consequently the vertebrae, which in with numerous sharp teeth—again patently the land-living ancestors of the ichthyo- a fish-catching device similar to that of the saurs were firmly held together by strong mesosaurs. It is an interesting fact that the articulating processes, had in these aquatic teeth of the ichthyosaurs show a labyrin- reptiles become comparatively simple disks, thine internal structure, quite obviously an similar in many respects to the vertebrae of inheritance from their cotylosaurian and fish. For in the ichthyosaurs there was no still more distant labyrinthodont pro- longer a problem of gravity to be met; the genitors. backbone did not have to act as a stiffening The eye was extraordinarily large. Evi- element supporting the weight of the body. dently these animals depended for the most The numerous skeletons that have been part upon vision to govern their movements. found show that the backbone in the Juras-

The eye opening of most fossil ichthyosaurs sic and Cretaceous ichthyosaurs extended shows a ring of small overlapping bones down into the lower lobe of the tail. When known as sclerotic plates. The function of these fossils were first discovered, it was these plates is not clear, perhaps they thought that the sudden downward bend of helped to protect the large eyeball. the tail might have been caused by an in-

As in all thoroughly streamlined swim- jury received during the life of the indi- mers, the ichthyosaurs had no neck worthy vidual. But as more specimens came to of the name. The head was an integral part light, always with the same sudden change

The long, pointed tail of the primitive Trias- smaller, but the front fin (here compared in sic ichthyosaur (left) attained the perfection separate drawings) developed into an effec- of a fishlike tail in the advanced Cretaceous tive stabilizing organ, just as it has in the ichthyosaur (right). The hind fin became quite unrelated sharks of today

Drawings by John C. Germann

Primitive Triassic Ichthyosaur Advanced Cretaceous Ichthyosaur in direction of the tail vertebrae, and as tiles are typically egg-laying animals. How more complete material revealed the fact could a marine reptile that never came out that this downward bend of the backbone on land reproduce by means of eggs? The was invariably enclosed within the lower answer would seem to be that the ichthyo- lobe of the fleshy tail, it became apparent saurs retained the eggs within the bodv—in that the development was natural. In the other words they were ovoviviparons so modern sharks the backbone bends up- that the voung were born alive. And there is ward, to enter the upper fleshy lobe of the good evidence to support this view. One tail, and this structure has been designated skeleton of an ichthyosaur in the American as a heterocercal tail. Therefore the down- Museum of Natural History shows the ward bending of the backbone in the skulls and partial skeletons of seven baby ichthyosaurs has been termed a reversed individuals within the body cavity of the heterocercal tail. adult. Thus it would seem that we have the

The reversed heterocercal tail was a record of a mother and her unborn young. specialization peculiar to the later ichthyo- Of course it may be answered that the saurs, for the earliest of these aquatic rep- ichthyosaurs, like so many reptiles, were tiles do not show any such structure. In the cannibals that practiced infanticide, and

Triassic ichthyosaurs the tail vertebrae still that these seven little ichthyosaurs are formed an almost straight line, and the merely the remnants of a large Sunday

fleshy tail evidently had but barely begun dinner. Naturally there is something to be

its development along lines that eventually said for this argument, but the weight of

were to form of it a deep scull, similar to the evidence would seem to be in the other

the tails in our modern fast-swimming fish. direction. Of particular importance is the The limbs of the ichthyosaurs were fact that one small skull, quite uninjured paddles, and in accordance with this spe- either by teeth or by the effects of gastric

cialization the limb bones had become very juices, is located between the pelvic bones short, while the bones of the "hands" and of the adult in the exact position that might "feet" were flattened hexagons or discs, be expected of an infant in the process of closely pressed to one another to form a being born.

solid internal support for the fins. Here is Throughout this description the ichthyo- an outstanding example of transformation saurs have been compared with fishes and in evolution. porpoises, and indeed, these animals offer The fore limbs were large and the hind one of the best examples of convergence in limbs relatively small. evolution—of the similar development of From this review of the anatomy in the unrelated forms. The modern shark, the

ichthyosaurs it is evident that these animals Jurassic ichthyosaur, and the modern por-

were completely aquatic, living their entire poise are all remarkablv alike in external

life in the water. In this they were similar form, because all of them have lived the

to the fishes with which they were con- same kind of life. And the requisites for temporaneous and to certain mammals, the that type of a life are very strict. Fast move- modern whales and porpoises. The ques- ment through the dense watery medium tion arises then as to the manner or method imposes a streamlined design, whether the

of reproduction in the ichthyosaurs. Rep- object be a fish, an ichthyosaur, a porpoise,

108 a torpedo, or a submarine. So it was that the reptilian through and through; the porpoise ichthyosaurs became fishlike because they skeleton and the details of its soft anatomy lived like fishes. In a like manner, the are mammalian through and through. The modern porpoises are fishlike, even though ichthyosaur came from land-living reptiles, they are warm-blooded mammals, because probably certain cotylosaurs. The porpoise they live like fishes. has come from land-living mammals, prob- Yet underneath the skin the animal gives ably from certain carnivorous types. The himself away. The ichthyosaur skeleton is course of evolution has been reversed; the

The aquatic Sauropterygians. Nothosaurus, a Trias- sic form, was partially terrestrial and partially aquatic. Elasmosaurus was a Cretaceous plesiosaur. Placodus was a Triassic mollusk-eater

Restorations by John C. Germann line of development that had its beginnings aquatic reptile, that shows in its develop- in the water and emerged onto the land, has ment the most definite evolutionary steps finally returned to the water. The course of toward the plesiosaurs and their relatives. evolution has been reversed, yet evolution Thus (as in the case of the ichthvosaurs)

is irreversible. For even though the ichthyo- the plesiosaurs, which abounded in the

saur returned to the water to live like a fish, waters of the Mesozoic era, were descended

it remained a reptile—it merely imitated a from land-living ancestors. Like the ich-

fish. No matter how fishlike it might appear thvosaurs, the plesiosaurs had completed a

on the outside, it had the reptile's structure cycle of evolutionary development.

underneath. It had the reptile's bones and The nothosaurs of Triassic age found in

brain, the reptile's heart and lungs. The Europe were among the first of the saurop-

organization and economy of the fish had terygians to appear. These were aquatic

been lost, never to be regained; this was an reptiles, but their adaptations to life in the air-breathing reptile, which though fishlike water were not complete. While they had

in form, retained in its structure the un- many characteristics that are seen in the

mistakable evidences of its terrestrial origin. later plesiosaurs, it is evident that they were

still partially land-living. Like the sea lions

of our modern California coast, the long The Euryapsida bodied, long necked nothosaurs could use The most important subdivision of the their short, web-footed limbs to haul them-

Euryapsida was that of the Sauropterygia selves out onto the rocks. Like the sea lions, (sawr-op-ter-ij-e-ya) containing the notho- they probably lived in and out of the water.

saurs (NOTH-o-sawrs), plesiosaurs (pLEES-i- It may be that the nothosaurs were not o-sawrs), and placodonts (pLAK-o-dahnts), the actual ancestors of the plesiosaurs, but of which groups the plesiosaurs are by far they were fairly close to such ancestors. So the most numerous and the best known. In for all practical purposes we may consider these reptiles the diagnostic upper temporal the nothosaurs as representing in a general opening or foramen was present, high up on way the stock from which the plesiosaurs the back of the skull, and bounded below developed. by the postorbital and squamosal bones. The first plesiosaurs appeared at the end

It is probable that these euryapsids de- of the Triassic period, and these animals veloped from a group of Permo-Triassic continued their development through the reptiles known as protorosaurs (prot-oi-o- Mesozoic era until, like so many other sawrs), comparatively small, lizard-like reptiles, they became extinct during the animals which show certain skull character- transition from the Age of Reptiles to the istics that would seem to suggest their Age of Mammals. But during the long position as ancestors of the later saurop- stretch of Jurassic and Cretaceous times the

terygians. An ancestral stage probably is plesiosaurs shared with the ichthvosaurs, seen in Aracoscelis (air-e-oss-seel-is), from mosasaurs, and a few other types the the Permian of North America, a land-living dominance of the water, so theirs was a

animal, evidently rather lizard-like in its successful chapter in the long story of

habits. However it was the European Per- vertebrate evolution. mian form, Protorosaurus, seemingly an Although the plesiosaurs were thoroughly

110 adapted to life in the water—indeed, it is That the plesiosaur mouth was a fish trap, doubtful that they ever came out upon the whether short or long, seems obvious, for it land at all—their construction was quite was armed with many long, sharply-pointed different from that of the ichthyosaurs. teeth—ideally shaped and arranged for Whereas the ichthyosaurs were "pseudo- holding onto such slippery objects as wet fish," swimming rapidly in pursuit of prey, fish. and were fishlike in form and habits, the In the limbs and feet of the plesiosaurs plesiosaurs were "pseudo-marine turtles" we see adaptations parallel to, yet quite that sculled along at a relatively slow pace. different from, those in the ichthyosaurs. In The comparison of the plesiosaur with a both groups of reptiles these members marine turtle is not exactly accurate, for formed paddles, but it would seem prob- the plesiosaurs were quite different in many able that the ichthyosaur paddles were respects from any modern animal whose balancing planes, like the fins of fish, habits are well known to us. True enough, whereas the paddles of the plesiosaurs were like the turtle, the plesiosaur had a broad, rowing paddles or oars. Consequently the flattened body equipped with huge rowing limbs in the plesiosaurs were never paddles. But unlike the turtle it carried its shortened to the degree that is seen in the head on the end of a long, snakelike neck, ichthyosaurs; rather they were elongated and there was a moderately long tail. In like oars, to give the necessary leverage for fact, a plesiosaur has been described by one rowing. The finger bones, though multiplied of the earlier writers as "a snake strung in number and compressed, were always through the body of a turtle." long—never the flattened discs that are seen

It would seem that the plesiosaurs in the ichthyosaurs. paddled along the surface or just beneath it, An interesting development in the plesio- propelling themselves with long, slow saurs is to be seen in the form of the strokes of their oarlike limbs. Moving along shoulder and hip girdles, which were very in this fashion they were able to dart the heavy and strong. These structures afforded head from side to side to capture the fishes attachments for powerful muscles that that probably constituted the bulk of their moved the oarlike limbs back and forth. diet. Moreover, provision for equally strong The skull in the plesiosaurs was either muscles both in front of and behind the small and short, or elongated with a sharp fulcra for the limbs enabled the plesiosaurs beak in front of the eyes. The plesiosaurs to "back water" as well as row forward. with short skulls had an extraordinarily long Whatever their actions may have been, they and flexible neck, which enabled them to must have been interesting to watch. How- flash the head this way or that for catching ever, there was no one to watch them the ever elusive fishes upon which they except other plesiosaurs or ichthyosaurs, fed. Those plesiosaurs usually called plio- whose powers of comprehension would saurs, with elongated skulls, had compara- hardly permit them to puzzle about the tively short necks, but it would seem mechanics of plesiosaurian locomotion. probable that the long rostrum or beak and Related to the plesiosaurs were the its greater gape of the jaws compensated for Triassic placodonts. typified by the Euro- the lesser reach and flexibility of the neck. pean genus, Placodns. These were thor-

111 oughly aquatic reptiles, adapted to a diet of while a related form, Placochelys (plak-o- mollusks and other shellfish, for their skulls KEEL-is), was covered turtle-fashion with a and jaws were equipped with broad, flat strong shell. crushing teeth. The paddles were relatively weak, so these animals must have been The Mosasaurs slow swimmers. Why should they need to swim rapidly, since their days were spent The ichthyosaurs, plesiosaurs, and their coasting along the bottom of shallow relatives were the inhabitants of the waters waters, picking up the Mesozoic brethren in Mesozoic times. They ruled the open of our modern oysters, which were virtually seas and the large lakes, where fish and stationary? There may have been some mollusks abounded and where the great aquatic enemies to bother Placodus and his land-living dinosaurs were curious objects relatives; if so these predators would find to be seen upon a distant shore. Yet abun- the placodonts rather tough eating. For dant as they were, the parapsids and Placodus had heavy dorsal ribs and a euryapsids had to share their dominance of strong "basket" of abdominal ribs that the water with certain other Mesozoic rep- offered considerable protection to the body, tiles. Of these, the most numerous and

The giant mosasaur Tylosaurus, of the Cretaceous seas of western North America Restoration by Charles R. Knight aggressive were the mosasaurs (MOSE-a- sized reptiles. But the mosasaurs, which sawrs)—the "sea-lizards" of Cretaceous went down to the sea, left behind them times. They were literally sea-lizards, for that problem of gravity that is ever present they were nothing more nor less than to plague and limit the land-living verte- lizards that became completely adapted to brates; therefore they were able to grow an aquatic life, and in doing so grew to big with impunity, and a good thing too, great size. for they lived in a world of giants. The lizards and their close cousins, the The skull suffered few changes in the snakes, are specialized members of the transition from a land lizard to a sea-going diapsid subclass of reptiles, and in their type. In fact, it was for the most part a modern, and to us their more ordinary, lizard skull grown large, with a pair of manifestations they will be considered upon dorsally located nostrils (always an ad- a later page. They appeared in late vantage to a swimming animal) as about the

Mesozoic times, approximately 130 million only concession to a life in the ocean wave. years ago, and early in their history one The body was elongated and flexible, and family of lizards, the mosasaurs, separated the tail, especially, was very long. The from their land-living relatives and re- presence of long spines on the tail vertebrae turned to an aquatic mode of life. And like indicates that the tail in the mosasaurs was the other groups of aquatic reptiles that we narrow and deep, obviously well adapted have already examined, the mosasaurs be- for propelling the animal through the came highly specialized in body design for water. Thus it is evident that the mosasaurs, their life in the open sea. Like the other like the ichthyosaurs, imitated the fish in aquatic reptiles, they show their true rela- their movements, using the body and tail tionships, for beneath the elongated, fish- for propulsion and depending upon the like form, with all of the various adapta- paired limbs for balance. The mosasaurs tions that go with this great transformation never went quite so far as did the ichthyo- from a land -living to water-living verte- saurs. They never attained a truly fishlike brate, the mosasaurs were lizards—lizards form in body and tail; they were sea ser- related to the varanids, the large "moni- pents, long and sinuous. tors," which live at the present time in the The paired limbs, as is usual among Old World. aquatic vertebrates, were paddles, with the The mosasaurs were all sizable animals, limb bones shortened and finger bones and some of them were truly gigantic. flattened to form the internal support for

Tylosaurus (tile-o-SAWR-us), for instance, the thin and flexible fins. from the Cretaceous of Kansas, was more The mosasaurs lived about 75 million than twenty feet in length—as large as a years ago in Upper Cretaceous times, at a medium-size whale and equal in bulk to period of general submergence, when shal- many of the dinosaurs of the day. In this low inland seas encroached upon the con- increase in size over their land-living fore- tinental areas. For instance, the American fathers, the mosasaurs demonstrated very mosasaurs are found in the Niobrara for- nicely the relationship between design, mation, an extensive deposit of shallow- environment, and size. All the land-living water marine beds covering great areas of lizards were and are small- to moderate- our western states. This encroachment of

113 shallow seas over much of western North upon him the costs of the court action. America was, geologically speaking, a fairly Doctor Goddin's victory was, however, rapid and brief event. Likewise, the rise rather short-lived. During the French in- and dominance of the mosasaurs was rela- vasion of Holland in 1794, Maastricht was tively rapid and short-lived. As compared bombarded, but the suburb in which Doc- with the evolution of their Mesozoic contem- tor Goddin lived was mysteriously spared. poraries, the mosasaurs were almost ephem- He suspected that the French had orders eral. But while they lived they lived well. to capture the mosasaur skeleton, so he hid

The name mosasaur comes from the it in a vault where the conquerors were scientific name of one of the first described unable to find it after the surrender. The members of this group of aquatic lizards, search became intense, and finally a reward

Mosasaurus. And this name in turn is based of 600 bottles of wine was offered for the in part upon the Meuse River where the much sought after fossil skeleton. This had first of these fossils was discovered. its effect. In short order a group of French

Incidentally, there is an interesting story grenadiers appeared with the fossil, and it connected with the discovery of the first was carted away to Paris, to be installed in mosasaur, and its subsequent fate. The the Jardin des Plantes. The name Mosa- skeleton was found in 1780 in a subter- saurus was given to the specimen by the ranean gallery of the large sandstone quar- English paleontologist, Conybeare, in 1828. ries of Pietersberg near Maastricht, Hol- land, and of course it immediately aroused The Marine Crocodiles a great deal of interest among the quarry- men who were working there. When it The crocodiles will be discussed on a was realized that an important scientific succeeding page, so it is not necessary to specimen had come to light the quarrying go into detail here. It should not be for- operations were suspended, and Doctor gotten, however, that some of the crocodiles Hofmann, a French Army surgeon who had of Mesozoic times took to the open water previously collected fossils in this quarry, and became truly marine reptiles. They was notified of the discovery. Doctor Hof- shared the dominance of the Mesozoic seas mann soon arrived, and immediately took with the ichthyosaurs and the plesiosaurs— charge of the fossil, directing its excavation although it is probable that they never with such skill that the entire skeleton was existed in such numbers as did these others. removed in a single block of stone. Like all of the other marine reptiles we

At this point in the proceedings a cer- have seen, the marine crocodiles, or geo- tain canon of Maastricht, a Doctor Goddin, saurs (jEE-o-sawrs), became specialized decided that the fossil should belong to along certain characteristic lines. The body him, since he owned the lands above the became long and flexible. Curiously quarry. So he claimed it, but Doctor Hof- enough, there developed a downward bend mann naturally refused to surrender the of the spinal column in the tail region, so treasure. The matter went to court, where that the tail assumed the "reversed hetero- the judge decided against Doctor Hofmann, cercal" condition that was so popular with not only making him hand the specimen the ichthyosaurs. The limbs, as might be over to Doctor Goddin, but also imposing expected, developed into flattened paddles.

114 14

Decline of the Dinosaurs

did the dinosaurs become ex- their natural evolutionary development.

Whytinct? This is a question to which The dinosaurs are a case in point. evolution f there are many answers. So-called racial senescence in

It is a complex question because the ex- is usually accompanied by overspecializa- tinction of the dinosaurs was a complex tion—by the production of bizarre forms process involving many different but re- which appear to be in no way well suited lated factors. Consequently, a short and to their environment. It may be that the simple answer to the question of why the chromosomes, those carriers of heredity, get dinosaurs should all have become extinct is "out of control" just before the extinction not to be had. Rather it is necessary to ex- of a group—indeed, overspecializations due amine the problem from several angles— to chromosomal upsets may have been in- to try to visualize, if possible, those factors strumental in causing the disappearance of which may have contributed to the dis- many particular evolutionary lines. appearance of a once mighty line. Some such factor might have been op- Perhaps the most general explanation for erative in the decline of certain lines of the extinction of the dinosaurs would be dinosaurs, especially those that died out that these great animals were unable to before the end of Mesozoic times. For in- adapt themselves to changing conditions. stance, some of the armored dinosaurs de- They were too fixed in their organization veloped peculiar projections and excres- to change in a changing world, so they were cences over the body and then became ex- left behind in the long race of animals tinct before the end of the Age of Dino- through geologic time. They could only saurs. succumb to other more progressive animals; On the other hand, most of the dinosaurs their reign upon the land was at an end. lived on until, or near, the end of Creta-

Now this is all very fine, but after the ceous times, and among these late forms explanation has been stated in this way it were some of the most bizarre and remark- still hasn't told us much; we are left with able of all the strange beasts we know by many questions in our mind. So it is neces- this name. So the factor of "racial senes- sary to go into the problem still further. cence" cannot be called upon as an ex- One factor that may have contributed to planation for the extinction of more than a the downfall of the dinosaurs is something few of the lines of dinosaurian evolution. that is often called "racial senescence," or This is all the more true when we remem- racial old age. The dinosaurs died out be- ber that most of the dinosaurs disappeared cause as a group they were old and had rather suddenly, geologically speaking, reached the end of their rope. In looking near, or at, the end of Cretaceous times. We through the pages of geologic history we must look to other causes for our explana- see frequent instances where animals tion of this interesting phenomenon. seemed to perish because they were senes- It may be that the relationship between cent, because they had reached the end of the very small and lowly organized brain

115 and the great bulk of body was one factor tant this factor may have been in causing operating to bring about the disappearance the ultimate complete decline of the dino- of these great reptiles. In late Cretaceous saurs is a question of considerable uncer- times the mammals were developing at a tainty. rapid rate, and these animals, although in- Another factor that must be taken into significant in comparison with the dinosaurs account is that of internal causes. For in- so far as size is concerned, were neverthe- stance, the downfall of the dinosaurs may less large-brained, active forms. As con- have been brought about in part by upsets trasted to the mammals, the dinosaurs were in their glandular secretions. As an ex- virtual walking automatons. Consequently ample, many of these animals had extraordi- there may have been a triumph of "brain narily large pituitary bodies at the base of over brawn." the brain. It has been found that in modern Again, the dinosaurs, being reptiles, were animals the pituitary body secretes the probably cold-blooded animals, just as our growth hormone, so that the large size of modern reptiles, while the mammals, be- the pituitaries and the general development coming of ever-increasing importance in of giantism in the dinosaurs went hand-in- late Cretaceous days, were warm-blooded hand. The dinosaurs were large because beasts. This means that the dinosaurs were they had over-developed pituitary glands— ponderous, sluggish giants as compared but what caused the over-development of with the small but very active mammals. the pituitaries is something else to specu- Moreover, the dinosaurs, being cold- late about. Perhaps we might blame that blooded, would fatigue easily, just as mod- on the chromosomal disarrangements, men- ern reptiles soon tire under stress of con- tioned above, but to do so merely pushes tinued activity. Such animals would ob- the explanation back another step. At any viously be at a great disadvantage in the rate, it is quite possible that in the dino- struggle for dominance with their warm- saurs with such large pituitaries there may blooded mammalian competitors, because have been common disturbances of the a warm-blooded animal can maintain its ac- hormone secretions with resultant deleteri- tivity over protracted periods of time. ous effects upon the animal. It is doubtful, All of this adds up to the fact that the however, whether such a factor was very small-brained, cold-blooded dinosaurs were important in causing the disappearance of competing with the large-brained, warm- the dinosaurs. Moreover, not all of the di- blooded mammals, and the more efficiently nosaurs were giants. organized animals won out in the end. Again, it is possible that epidemics may In this connection, the idea has been have been a contributory cause, in some frequently advanced that the destruction cases. This is something that can only be of the dinosaurs was brought about in part guessed at. by small mammals that preyed upon the Thus we are able to speculate along vari- eggs of the huge reptiles—that the extinc- ous lines of thought, and by so doing we tion of the dinosaurs was hastened because can find numerous causes which, working increasingly great numbers of them were together, may have contributed to the ex- never born. It is quite probable that such tinction of the dinosaurs. No one of them may have been the case, but how impor- alone would seem to be sufficient to explain

116 it, but a combination of them might offer of time to make the change in diet that sufficient reasons for the disappearance of would have enabled them to live on in a these animals from the face of the earth. modern world. And with the herbivores

However, there is one line of evidence went the carnivores. Moreover, all of the that is quite out of the realm of speculation. dinosaurs, it would seem, were unable to At the end of the Cretaceous and the begin- adapt themselves to the temperature ning of the Paleocene periods occurred a changes that were taking place. So they new series of events of profound importance became extinct. to the more recent stages of Earth History. But why did they all become extinct? For this was when our modern mountain Why didn't a few of them survive and systems were born—when the young persist through the Age of Mammals, even Rockies began to thrust themselves up into to our own day? Their close cousins, the the blue sky out of a land that had been crocodiles, did persist, and it would seem low and flat. reasonable to think that some few of the

This isn't to say that there was a sudden lines of dinosaurian evolution might have eruption of Wagnerian fireworks, with hot survived. Maybe there is something in the lava spouting all over the place and earth- idea of racial senescence after all! quakes rocking a patient and suffering land- It is an interesting fact that the dino- scape. Indeed, quite the reverse. To our saurs weren't the only reptiles that failed to modern eyes, accustomed to the contrasts survive the Cretaceous-Eocene transition. of blistering summers and frigid winters, Although many of the crocodiles were able of flat plains and jagged mountains, it was to weather this great break in geologic a period of great tranquillity. It would history, certain crocodilians disappeared have seemed like a time of perpetual mel- like the dinosaurs, at the end of Creta- low summer amid gentle scenery. Yet the ceous times. So did the pterosaurs, the changes were taking place, slowly but in- flying reptiles so closely related to certain exorably. No individual animal would have dinosaurian lines of evolution. So did the noticed them, nor several generations. But aquatic plesiosaurs and the giant aquatic the cumulative effect was there, genera- lizards, the mosasaurs. The ichthyosaurs be- tion after generation and millennium after came extinct even before the end of the millennium. The tropical lowlands gave Cretaceous period. way to rolling uplands. Palms retreated be- Thus the Cretaceous-Eocene transition fore the hardwood forests. The warm, was a period of general reptilian extinction. equable temperatures of the tropics were It was a period when the giant reptiles on gradually replaced by the fluctuating tem- land and in the sea—the dominant animals peratures of more temperate climes. In of the Mesozoic scene—gave way to the fact, the worldwide tropical climate of oncoming mammals. Their day was over, Mesozoic days began to be replaced by the and so far as reptiles were concerned, the zonal climates of the Cenozoic. future was to belong in the main to the

And these were changes to which the relatively small animals that we know to- dinosaurs could not adapt themselves. The day, the lizards and snakes and turtles, al- great plant-eating dinosaurs seemingly were though a limited number of the large croco- unable in a relatively short geological space diles persisted.

117 15 The Survivors

Crocodiles, Ancient and Modern forebear has been named Protosuchus o us, living in the age of steel and (prot-o-sooK-us). Tl airplanes, the Age of Dinosaurs seems Protosuchus was relatively small, no

very distant indeed, yet even in the larger than a medium-size lizard. It was a modern world, where man flies to the re- diapsid reptile, related closely to the theco- motest corners of the continents and the donts, the little bipedal animals which, it oceanic islands, and where he cuts his way will be remembered, were ancestral to the into the densest and most primitive of dinosaurs. But in spite of its ancestral heri- tropical jungles with complex machinery, tage, Protosuchus was already on the way there still live some survivors from that dim, to becoming a crocodile, as is shown by past era of Earth History. These are the various features of the skull and skeleton. crocodiles and their relatives. Crocodiles It had a rather short head, with compara- were contemporaries of the dinosaurs, and tively large eyes and a pointed nose. The they have persisted into modern times with limbs were typically crocodilian, even in but little change in form or habits. And by this ancestral beast, and it is interesting to studying the crocodiles, especially their see that the hind limbs were much larger habits and their several modes of life, we than the fore limbs, a reminder of its two- can get some inkling as to the mode of life legged thecodont ancestry. Perhaps the of the dinosaurs, because the modern croco- most striking feature of this little reptile diles have preserved a Mesozoic manner of was the heavy armor with which it was living in what continues to be an essentially protected—large rectangular plates, or Mesozoic environment. scutes, on the back, on the belly, and sur-

To get a full and comprehensive picture rounding the tail. of the crocodiles it is necessary to go back This grandfather of the crocodiles needed to the Triassic, the period when the ruling his armor, for he lived in a region that was hierarchies of Mesozoic reptiles were first inhabited by the large phytosaurs—those arising, because the crocodiles, like the di- specialized thecodonts which, it will be re- nosaurs, the Mesozoic marine reptiles, and membered, anticipated and paralleled in other rulers of the middle period of Earth Triassic times the later true crocodiles. Here

History first appeared in their most primi- was an interesting situation—the ancestor of tive manifestations at that time. the real crocodiles, a small, lizard-like The earliest known animal that we may armored reptile, living a precarious exist- call a crocodile was a little Triassic reptile ence in the continued presence of the giant found a few years ago near Cameron, "precrocodiles," the phytosaurs—the scaly, Arizona, represented by a remarkably well toothy, stream-living monsters of those dis- preserved skeleton, with virtually the entire tant days. It was a life-and-death race, in bony structure present and in addition which the hunter came out second best, for much of the dermal armor which covered his kind soon became extinct, while the back and the belly. This crocodilian strangely enough, the little, inoffensive vie-

118 tim was the progenitor of a line that even- ence, for the crocodiles have watched the tually became remarkably like his phyto- dinosaurs arise and decline, they have seen saurian nemesis, the line of the crocodiles. the mammals evolve almost from their first The real deployment of the crocodiles beginnings through the early stages of their began in the Jurassic period, and from that radiation, to the present high point in their time to the present these reptiles have in- development. As a last and fleeting incident habited the tropical streams and swamps of in their long existence upon the earth, the the earth. Generally speaking, the croco- crocodiles have seen man develop from diles may be described as large elongated, his primate forebears, to go through thou- armored, meat-eating reptiles, spending sands of years of primitive cultural exist- most of their time in the water, but capable ence and finally to attain his present state of active and aggressive movements upon as the creator of a highly complex civiliza- land. The crocodiles float down streams, tion. with only the eyes and the nostrils pro- The evolution of the crocodiles was two- truding above the surface of the water, fold. There was first a Mesozoic radiation ready to snap up instantly any hapless ani- of these animals, the Mesosuchians (mes-o- mal that may come within range of their sooK-e-yans), beginning with the Triassic widely gaping and powerful jaws. It has ancestors like Protosuchus and extending been a highly successful pattern for exist- through Jurassic and Cretaceous times to

Ancestor of the crocodiles, Protosuchus. It was a primitive reptile, but many of its features show that it was already on the way to becoming a crocodile

Restoration by John C. Germann from a model by Louise Waller Germann produce a great variety of crocodilian adap- diles, in which animals derived from some tations suited for life in differing environ- of the typical Jurassic types gave rise to ments. the modern crocodilians or Eusuchians

The first real crocodiles, as contrasted (yoo-sooK-e-yans) ("True-Crocodiles"). The with the ancestral crocodiles of the Triassic, first eusuchians were small, but they were appeared in Jurassic times. These ancient the progenitors of a successful line of large, members of the order lived along streams active reptiles. By the end of the Creta- and in lakes, as do our modern crocodilians, ceous the three groups of modern crocodili- and many of them would seem to have been ans had appeared, namely the pointed- inhabitants of the seashore, or even of the snouted crocodiles, the broad-snouted al- open ocean. As in modern times, there ligators, and the very narrow-snouted gavi- were long-snouted crocodiles and short- als. Indeed, the eusuchian pattern was well snouted crocodiles. They were all active set in the Cretaceous, for there has been hunters that prowled along the banks and very little significant change in the croco- the strand, or even ventured out into the dilians since that date. open waters, constantly in search of any Of the modern crocodilians, the long- reptiles or fish that might serve to alleviate snouted gavials (Gavialis) (gave-e-AL-is) of in part their insatiable appetites. Like the India, Borneo, and Sumatra are the largest. modern crocodiles, these ancient saurians There are records of gavials having a length were active predators, a constant threat to of 30 feet, which makes them the giants all of their contemporaries that might fre- among modern reptiles, and indeed, reptiles quent watery places. Teleosaurus (teel-ee- of no mean dimensions when compared o-sawr-us) was typical of these early croco- with some of the large dinosaurs. dilians. Of almost comparable size are some of One interesting development already the present-day pointed-snouted crocodiles, mentioned on page 114, which has never such as the great salt-water crocodile been repeated by later members of the (Crocodilus) (krock-o-DiLE-us) of India. group, took place among the Jurassic croco- These crocodiles, using the term in its nar- diles. This was an adaptation to a purely row sense, are found in a variety of forms marine type of life, characterizing the and sizes in tropical regions around the crocodilians known as the geosaurs. These world in Africa and the Orient, in Australia, metriorhynchids (met-ree-o-RiNK-ids) were and in North and South America. long-snouted, long-bodied crocodilians, Among the crocodilians, perhaps the with the feet modified as paddles and the giant of all time was the Cretaceous croco- tail a fishlike scull that served to propel dile, Phobosuchus (fobe-o-sooK-us). This the animal through the water. gigantic animal, not unlike the salt-water Some of the Mesozoic crocodiles failed crocodile and other members of the genus to survive from the Jurassic into the Creta- Crocodilus in form, had an enormous skull ceous; others were characteristically Creta- more than six feet in length. The entire ani- ceous in their development and failed to mal must have been some 50 feet long, survive into the Cenozoic. which made it one of the most dangerous Then there appeared in Cretaceous times and feared predators of Mesozoic times. the second great deployment of the croco- The alligators are perhaps the most

120 highly developed of the modern crocodili- ya) ("Beak-Heads"), so named because of ans. These reptiles are represented at the the rather deep, beaklike construction of the present time by the alligator (Alligator) in front of the skull. The first rhynchocephali- North America and China, and by the ans made their appearance early in the his- caimans in South America. The fossil evi- tory of the diapsid or two-arched reptiles— dence indicates that alligators once were in Triassic times—and from that ancient common residents over much of North date they established a line of evolution America and Eurasia. which, if not particularly important, at least

had the virtue of a long life. The Long-Persistent Although related to the dinosaurs, the Rhynchocephalians Rhynchocephalia were never large reptiles. They were the modest members in a tribe Living along the high, rocky coasts of that was generally characterized by size

New Zealand is a small, lizard-like reptile and impressiveness, and were outwardly which is a lonely survivor from the distant more or less lizardlike, from their begin-

Age of Reptiles. This is the little tuatara, nings to the present single survivor, the known scientifically as Sphenodon (sfen-o- tuatara. don), which in spite of its outward re- In late Cretaceous and early Eocene semblance to the lizards is in truth a distinct times there lived a comparatively large type of diapsid reptile. rhynchocephalian, the genus Cfiampso-

Sphenodon is the final survivor of a very saurus (camp-so-SAWR-us). This member of ancient order of reptiles, that group known the order was an animal some four or five as the Rhynchocephalia (rink-o-sef-AY-le- feet in length, and it was characterized by

Sphenodon A survivor from the distant age of reptiles, the tuatara of New Zealand, and his ancient relative, Champsosaurus. Although related to the dinosaurs, the Rhyncho- cephalia, to which both belong, were never very large. The tua- tara has vestiges of a third eye in the center of its forehead

Restorations by John C. Germann

Champsosaurus the long, gavial-like compressed pointed the geckos that live in houses of the tropi- snout. cal east, and the peculiar tree-living chameleons. Even though the lizards are now spread far and wide over the tropical The Lizards and Snakes and temperate reaches of the globe, they To many of us the word "reptile" means are not particularly important paleontologi- one thing, and that thing is a snake. To cally. some of us it may mean two things, a snake The snakes are nothing more than highly and a lizard. Certainly snakes and lizards specialized lizards—lizards in which the legs are the commonest and the most widely have been lost and the skull highly modi- distributed of modern reptiles, known to fied. Like the lizards, the snakes would almost all people except perhaps Eskimos seem to have made their appearance in and Irishmen, and commonly regarded Cretaceous times, since which time they with mixed feelings of disdain and horror, have spread over the earth and become quite undeserved on the part of the poor specialized in a variety of ways. reptiles. Unfortunately the fossil record of the

These reptiles belong to the order Squa- snakes is extremely scanty. These reptiles mata (skwa-MAH-ta), in which are included lived in environments such that their bones the extinct Mesozoic marine reptiles, the were rarely preserved, and when they were, mosasaurs (described in Chapter thirteen). they were scattered so that isolated verte- The Squamata are essentially modified brae usually form the only records available diapsid reptiles, in which the bony border to us. The skull in the snakes has been from of the lower opening behind the eye, the the beginning such a specialized and lateral temporal fenestra, has been lost. fragile apparatus that it is rarely found as

The lizards are the more primitive of the a fossil.

Squamata. We know them well, so there is Putting the fossil evidence together and little needed in the way of description. combining it with our knowledge of recent

Typically the lizards are elongated, sprawl- snakes, it would seem that the most primi- ing reptiles, living close to the earth and tive of these strange vertebrates are the hunting their prey there. The monitors of boids, the large constrictors including the the Old World, of which the genus Varanus boas and pythons of the tropics. In these

(var-AN-us) is characteristic, are typical liz- snakes there are numerous teeth, and the

ards, and it was from forms such as these skull more nearly approximates the lizard that the gigantic Cretaceous mosasaurs skull than in most other snakes. The most evolved. Indeed, the mosasaurs were noth- highly developed of the snakes are the

ing more nor less than monitors grown poisonous ones. In these snakes the skull large and specialized for an aquatic ex- has been greatly modified, and the teeth istence. At the present time the lizards show reduced, except for the large, specialized a variety of forms, the results of specializa- fangs, which are used to inject poison into

tions that have taken place since their first the intended victim. Terrifying as these appearance in Cretaceous times. There are poisonous snakes may be, they are none- the iguanids, living in deserts and along theless objects for admiration, for they dem- seashores, the agamids, the various skinks, onstrate most beautifully the high degree of

122 L n

specialization that may be reached through The reason for this dissimilarity is that the the processes of evolution. turtles have become highly modified rep-

Like the lizards, the snakes are of little tiles and it is by the very reason of these puleontological importance. modifications that the turtles have been able to live their lives down through the The Turtles ages, while so many of their former contem- poraries became extinct.

One group of reptiles, which seemingly The ancestry of the turtles is obscured in

belongs to the Anapsida, has persisted into the mists of geologic antiquity, but it is

our own times. This is the group known as probable that they were descended from the Chelonia (kel-owN-e-ya) or Testudinata certain generalized anapsid reptiles. There

(tes-TOOD-e-na-ta), the animals which we is preserved, albeit all too imperfectly, the commonly call turtles. remains of a reptile known as Eunotosaurus True enough, the turtles don't look much (yoo-note-o-SAWR-us), from South Africa, a like the primitive anapsids that inhabited reptile that would seem in many ways to

the world in Permian and Triassic times. fulfill the role of ancestor to the turtles.

Restorations by John C. German

Evolution of the Turtles

leuro

Cryptodira One line of modern turtles, the Pleurodira or side-neck The other, the Cryptodira turtles, is now found only in or vertical-neck turtles, is the Southern Hemisphere of broad distribution

The first true turtles ar« found in the Triassic period (between 155 and 200 million years ago), in the group known as the Amphichelydia

Amphichelydia

All our modern turtles evidently descended from the group of animals represented here by Eunotosaurus. Its rrbs were greatly broadened to form the beginnings of the upper shell. The ver- tebrae were reduced and transformed somewhat as in turtles

Eunotosaurus Eunotosaurus had a limited number of most completely the lengths to which evo- elongated bones in the spinal column very lutionary transformation has gone in these similar to the vertebrae of the turtles. And peculiar reptiles. The upper shell, or cara- what is more significant, Eunotosaurus had pace, of the turtle is formed of modified expanded ribs that touched one another, ribs that have grown together to form a ribs that appear to be the beginnings of the housing for the body. Now in normal verte- shell which is so characteristic of the turtles. brates the limbs and their girdles (the pec- Certainly by Triassic times (perhaps 175 toral and pelvic girdles) are outside the ribs, million years ago) the turtles had become but in the turtles, the limb girdles and the established upon the earth, for in the Trias- limbs themselves are under the shell, in sic of Europe is found a full-fledged turtle, other words, they are inside the highly Triassochelys (try-as-o-KEEL-is), an animal modified ribs. The method whereby this in which the pattern for turtle survival al- evolutionary hocus-pocus has taken place is ready had become well set. From Triasso- shown by the development of the modern chelys to the present, the story of the turtles turtle within the egg. It is evident that at a has been a relatively static one, a story of certain stage of turtle development the some reptiles that were able to pull in their transverse or side-to-side growth of the ani- necks and their legs and their tails and mal is very rapid, and takes place in such within the protection of their hard shells a fashion that the ribs actually grow out to survive the vicissitudes of life through and over the limb girdles. long periods of geologic time. Add to this upper shell, or carapace, of

The turtle skull is seemingly an anapsid transformed ribs the lower shell, or plas- skull modified by the loss of many bones tron, and you have the pattern of turtle and by the marginal notching of the back survival. of the skull. In accordance with this gen- From the primitive turtle ancestors such eral trend of reduction in the turtle skull, as Triassochelys, modern turtles have devel- the teeth have been completely suppressed, oped along two main lines. One is that of and their function has been taken over by our northern turtles belonging to the group a horny beak that encloses the bones of the Cryptodira (KRiP-tow-dire-a), in which the jaws. The turtle limbs seemingly are modi- neck is withdrawn into the shell by a verti- fied anapsid limbs, and it may be that in the cal flexure. The other is the group of peculiar right-angle pose of these limbs we Pleurodira (PLUR-o-dire-a), living in the see a retention of the pose that character- southern hemisphere; in these the neck is ized the primitive reptiles. withdrawn into the skull by a side-to-side

It is the turtle shell, however, that shows flexure.

124 16 Why Study Fossils?

ur story is ended. We have seen in to some extent upon the identification of brief review the manner in which earth strata as interpreted by the study of

the first land-living vertebrates various types of fossils. Yet even taking arose; we have surveyed the development these aspects of paleontology into account, of the early reptiles and have seen how it can still be said that much of the study from them those of Mesozoic creation, the of fossils yields no direct economic returns. dinosaurs, began, became dominant and So the question still stands. then disappeared forever from the face of The answer to the question is simply the earth; we have looked at the pitifully found, and it is this—man is a curious ani- few survivors that live on as a link with mal. In fact, if man were not so curious, past reptilian dominance. if he were not so interested in everything

Having done all of this, we may pause to about him, he wouldn't be man. It is the ask a question—what does this study lead very definite primate trait of poking into to? Why paleontology? Why devote the everything under the sun that has put us time and energy and the money to a science where we are. We have arisen to the heights that is so far removed from our contem- of our mental development, and correla- porary world as is the study of fossils? In tively to the present degree of our domi- these days of great world-shaking events, nance in the world, through the trait of why should we bother with the bones of wanting to know something about every- beasts long vanished? thing and thereby gaining such an under-

It is a good question. In our modern standing of the world about us as to world so troubled by the complications of enable us to achieve our position of un- machine-age wars and involved economic paralleled superiority over the rest of the situations, the study of fossils may appear at animal kingdom. To put it more simply, first glance to be rather distantly removed we are great because we understand our from the realities of life, and it is true that world, and we understand our world be- much of paleontology has little direct eco- cause we are curious about it. nomic significance. Of course some aspects The proper understanding of our world of paleontology are very important in in- depends in part on the proper understand- dustry. For instance the study of micro- ing of its past history, and for a proper un- scopic fossils, by which many layers in the derstanding of the past history of the earth earth's crust may be identified, is of the the subject of paleontology looms large. utmost importance to the petroleum indus- For instance, most people read newspa- try. Without the help of the "economic pers, not because of any monetary profit paleontologist" a great deal of the explora- that they may derive from the reading, but tory work for oil would be blind "wild- because they want to know what is going catting" rather than the well-planned, co- on in the world about them. The dissemina- ordinated effort that it is. Certain other tion of news and information is the primary aspects of economic geology, too, depend justification for a newspaper. Similarly, peo-

125 pie do not study history because of any stition cleared away. After the Renaissance,

definite predictable economic gains that man's cultural progress was rapid, because < may be made by such a study, but rather he was allowed to be curious.

because a knowledge of history is an aid This pursuit of knowledge inevitably and to the shaping of present-day conduct. We finallv produced the evolutionary concept wish to know what happened in the past, —a mode of thought which grew through partly for the pure pleasure of knowing the years, to be suddenly and gloriously how our ancestors behaved and partly for crystallized by Darwin in his great work,

the ability that it gives us to interpret pres- The Origin of Species. In the entire history ent-day events. In the same way, a knowl- of man, the year 1859, the year in which edge of prehistory, carrying the story back Darwin's work was first published, will al- even to the beginnings of life on the earth, ways be outstanding. The entire history of gives us an increased understanding of the life on the earth was from then on inter-

world in which we now live. That is the preted as an orderly process, subjected to function of paleontology. It is a science of the laws of nature, rather than as a series interpretation. It is a "cultural science" if of disjointed, catastrophic, and often con- you please, the knowledge of which gives tradictory events. to its possessor a magnificently broad view Thus was introduced a revolution in hu- of the world. man thought which has gradually spread

The student of paleontology is the man until today it forms a basic portion of our with a long view of things. "His field of cultural background. Indeed, the develop- vision embraces the whole of life. His time ment of the evolutionary concept has pro- scale is so gigantic that it dwarfs to insig- foundly revolutionized man's manner of nificance the centuries of human endeavor. thinking, just as in earlier days the dis- And the laws and principles which he stud- covery by Copernicus that the planets re- ies are those which control the whole great volve about the sun opened the eyes of stream of life, upon which the happenings his contemporaries to new horizons around of our daily existence appear but as little them. Darwin, like Copernicus, gave to man surface ripples." 1 a new and objective view of man's position

The world of primitive man is a world in the world about him and in the uni- filled with fears of the unknown, a world verse. in which the individual is surrounded bv So it is that paleontology needs no de- "gorgons, and hydras, and chimaeras dire." fense—it needs no justification. As long as

Such was the fantastic world that gripped man is interested in the world about him, and bound the mentality of medieval man. as long as he wants to know the past his-

And it was only through the rebirth of tory of this world, so long will he study knowledge and learning, by the free expres- fossils. Paleontology is a part of our modern sion once more of man's natural wish to cultural environment, it is a part of the learn about everything that he saw, or felt, great pattern of science and literature and or heard, that the mists of medieval super- art which has enabled us to know nature

as it has never been known before, and 1 Matthew, William D. "The Value of Palaeon- thus has made of us the "Modern Men" tology." Natural History Magazine, XXV (1925), No. 2, p. 167. that we are.

126 17 Where the Dinosaurs and Their Relatives are Found The dinosaurs, the dominant land ani- geologic periods when reptiles were domi- mals of Mesozoic times, were of world- nant on the land?

P wide distribution. They roamed This is not an easy question to answer, through the tropical jungles and waded for the answer must be based upon many through the low-lying swamplands that lines of evidence that are difficult of in- stretched across the continental land masses terpretation. In short, the answer must be in those distant days of world-wide cli- found in a study of paleogeography, the

matic uniformity. They were the ubiqui- interpretation of the face of the earth as it tous inhabitants of the earth, just as was in past geologic ages. today the warm-blooded, furry mammals The study of paleogeography is founded are the dominant land-living animals, to a large extent upon a study of sediments, around the world and almost from pole the rock materials such as limestones, sand- to pole. stones, and shales which were deposited at We know this because their fossil re- the bottoms of seas, lakes, rivers, and on mains have been found on all of the con- the dry land, originally in the form of limes, tinental land masses and in widely sepa- sands, and muds. These sediments are the rated degrees of latitude. They are found pages of the geologic record in which are in North and South America, ranging from contained many facts as to the past history the northern plains of Alberta to the south- of the earth. In them are preserved the ern plains of Patagonia. Dinosaur bones fossils which show us what life was like in have long been known from various parts former ages of the earth's history. of Europe, and in recent years they have It is evident that if all of the sediments been found in Africa and in Asia. In fact, that were deposited since the beginning of we find them in so distant and seemingly time were preserved, we would have a rela- isolated a land as Australia. tively complete history of the earth. Such

From this it is evident that during is not the case, for during the long existence Mesozoic times not only the climate but of our planet sediments have been sub- also the geographic conditions were differ- jected to the many vicissitudes of erosion ent from what they are today. Not only by water and wind, to deformation by the were climates uniformly tropical and sub- uplift of mountains, and to transformation tropical, thereby providing conditions of by earth processes of movement, pressure, temperature that allowed the reptiles to and heat. So the pages in the book of Earth spread over most of the continental land History are not nice, orderly, complete areas of the globe, but also there were pages, but rather are they torn and crum- connections between continents which do pled, and many of them are missing alto- not exist at the present time, whereby ani- gether. Therefore any attempt to recon- mal and plant life in those distant days struct the past history of the earth, the could cross from one region to another. extent of former continents, the extent of What was the earth like during the long former seas, and the distribution of the

127 animals and plants that lived on these an- ing of continental areas by shallow seas, cient continents and in these ancient seas, similar to the Mediterranean Sea of our involves the problem of piecing together own time, or by narrow oceanic arms ex-

many separate items to tell a logical story. tending into deepening troughs. It also re-

It is here that the factor of interpretation sulted in the retreat of the marine waters

enters, a factor that is determined by the during periods of uplift, so that the shallow mass of accumulated knowledge plus the continental shelves, now under water, were individual ability of the interpreter. There- frequently high and dry. Also, during pe-

fore it is easy to see that the subject of riods of uplift, there would be connections paleogeography, the interpretation of the between continental areas at places where former extent of land masses and ocean the seas are now shallow. This would in-

surfaces, is one in which there are bound to volve connections between North America be differing opinions. and Asia in the Rering Straits region, be-

This is particularly evident with regard tween North America and South America in to the stretch of some 160 or 180 million the Isthmian region, possibly between North years, from the Pennsylvanian period America and Europe across Greenland and through the Cretaceous period, which we Iceland, between Eurasia and Africa across may call the Age of Reptiles. That great the Mediterranean region, and between Asia portion of Earth History is so far away and Australia across the region now occu- from us in time that certain of its details pied by the East Indies. have been obscured by the geologic events A second group of paleogeographers, in- occurring since then. It is much easier to cluding many European authorities, consid- come to reasonably sound conclusions as ers that in past geologic ages, especially in to the manner in which the surface of the periods so distant as those of the Mesozoic earth was divided between oceans and era, the continents, though in general lo- lands during the Age of Mammals, than cated as they are at the present time, were during the more distant Age of Reptiles. nevertheless quite different in their relation- As a result various opinions have been ships to each other. According to this idea, reached as to the paleogeography of there were broad transverse connections be- Permian and Mesozoic times. In a general tween the continents, so that the land way, these opinions may be grouped into masses of the earth were arranged more or three schools of thought. One school, fa- less along east to west axes. There was a vored by most American geologists, consid- northern land mass including northern ers that during the past history of the earth Eurasia ("Palaearctis") and North America the continental land masses have retained ("North Atlantis"). Separated from this by much the same form and position they an equatorial sea, "Tethys," there was a have today. According to the followers of great southern continent, "Gondwana land," this theory, the differences in the actual including the eastern portion of South land and water areas between the present America, southern Africa, peninsular India, and past geologic periods can be explained and perhaps Australia. According to the by the up and down movements of broad adherents to this theory, the relationships continental blocks. This resulted during pe- as outlined above differed from time to riods of submergence in the periodic flood- time, sometimes these great land masses

128 existed—at others they were broken up by qualifying factors that enter the picture be- marine incursions. tween the death of an animal, say a dino-

Finally, there may be mentioned the fol- saur, and its ultimate discovery as a fossil.

lowers of the theory of "continental drift." In the first place, a great majority of numbered for the most part among some of animals that have died in past geologic ages the European geologists. According to this were never fossilized. Conditions had to be

theory, the land masses were at one time just right for a skeleton to be preserved—it contiguous, and animals roamed freely over had to be buried soon after the death of the one large continental area. Then there was animal, and the conditions of burial had a fragmentation of this great land mass to be favorable in order that the original and the continents drifted apart to their bone would be transformed into rock. present positions. Thus, an overwhelming proportion of the

This is not the place to go into the rela- animals that lived in past ages were elimi- tive merits of these contrasting theories. nated from the record at this stage of the

Suffice it to say at this point that the pres- process.

ent and past distribution of land-living ani- Then, for fossils to come down to us, it mals can on the whole be very satisfactorily was necessary for the sediments containing

explained upon the basis of the first of the them to be preserved. As we have seen, three theories outlined above, namely that sediments are frequently destroyed by

of continental permanence. It may be that erosion, or transformed in various ways by there was a southern continent of "Gon- different powerful earth forces. Many po- dvvanaland" during Permian and Mesozoic tential fossils have been destroyed bv

times, but it is not necessary to explain the events such as these. distribution of the reptiles of those times. Finally, in those sediments which are

The important fact is that during Per- preserved, we find only the fossils that mian and Mesozoic times there were cer- happen to be near the surface—that have tain periods when intercommunications ex- been sufficiently exposed by processes of isted between the continental areas, so rep- weathering and erosion that we are able to tiles were able to spread from one great find them. Here again, the proportion of region to another. That is why we find simi- the known to the whole is greatly reduced, lar reptiles in North America and Eurasia, for the fossils contained in the cubic content or in Europe and South Africa, or in Africa of any one geologic formation are vastly and South America. Even the slowest and greater in number than those exposed at most sedentary of the reptiles and amphibi- the surface where they will be found. ans were able to cover great areas because So it is evident that the fossils upon of the uniformity of climate, the lack of which our knowledge of past life is based geographical barriers, and the great length are but a tiny fraction of the whole of that of time involved. life. Even so, we may be sure that the

It must not be thought from this that picture we get from them is reasonably fossil dinosaurs or other reptiles are to be accurate, for small as may be the part to found wherever they once lived. Indeed the whole, it is nevertheless a random fossil localities are generally scattered in sample, which according to the probabili- their occurrence. This is due to the many ties of statistics is a rather accurate indica-

129 tion of the true situation. In other words, To get back to a statement made at the the fossils are a kind of prehistoric "Gallup beginning of this chapter, dinosaurs, their poll" of life as it existed on the earth in reptilian relatives, contemporaries, and former ages. predecessors have been found in various

Perhaps this may explain in part why localities all over the world, mainly as a dinosaurs and other fossil reptiles are not result of the studies made by geologists found anywhere and everywhere, why they and paleontologists during the past one are found in certain restricted localities. hundred years. Much of the earth's surface

Dinosaurs are found for instance, in is by now reasonably well known to the Wyoming and Colorado, because sediments students of Earth History, and in the better in which their remains have been preserved known areas it is probable that discoveries are exposed at the surface of the earth in of new fossil localities will in the future be those states. Dinosaurs are not found in less frequent than has been the case in the

Illinois because any sediments which might past. Even so, new discoveries will be have contained dinosaur bones have long made, even in the most thoroughly combed since disappeared, due to the erosive proc- areas. This has been and always will be esses of water and wind, and even of ice. one of the virtues and one of the interesting Dinosaurs are but seldom found in New aspects of the science of paleontology. In Jersey, even though sedimentary beds of the regions less well-known geologically the proper age are exposed in certain lo- (and there are still great areas falling within calities of that state. This is because condi- this category), there are still many great tions during the Age of Dinosaurs were not discoveries to be made. So it is that in a particularly favorable for the accumulation world shrinking geographically, owing to and fossilization of animal bones. There- modern methods of transportation and fore the sediments in which dinosaurs ought communication, there is much room for to occur are barren. paleontological exploration, particularly

Important Localities where Prehistori Amphibians and Reptiles have been Disa C(LX O ^ ^ o o 093

O Cretaceous (Between 60 and 120 million years ago) A Jurassic (Between 120 and 155 million years ago) ^ Triassic (Between 155 and 200 million years ago) n Pennsylvanian-Permian (Between 200 and 245 million years ago) X Devonian (Between 275 and 340 million years ago) ,

1

1. 1 The Fossi ns d of tin g c rs and Their Re! atives throughout the World 5' B £p w -o '5 B America -a B _2 B c| E E .2 ° a E • 2 N Ego s£ B . „ S§ B America a. at ~ 2 o w Eastern "C .2 •* 01 North r ° "Ki South « Ml o> 4- a> hi O O 1-Sl SU Us p, B o Sz z < «/)<— * ui ui

Devonian Carboniferous Carboniferous Permian Permian Carboniferous Permian Triassic Labyrinthodonts Iriassic — Permian — Triassic —Triassic —Triassic — Triassic —Triassic Cenozoic Cenozoic Cenozoic Cenozoic Cenozoic Jurassic Triassic Recent —Recent -Recent Frogs, toads, salamanders — Recent —Recent —Recent —Recent —Recent Carboniferous Carboniferous Carboniferous Permian Permian ... T • Cotylosaurs Triossic —Permian —Triassic —Triassic

Cretaceous Cretaceous Jurassic Cretaceous Cretaceous Cretaceous Cenozoic Triassic Permian Turtles -Recent - Recent — Recent —Recent —Recent — Recent — Recent —Recent — Recent Carboniferous Permian Permian Permian Pelycosaurs — Permian Permian Triossic Triassic Triassic Triassic Triassic Permian Permian Mammal-like reptiles —Triassic

Triassic — Triassic— Cretaceous Jurassic Cretaceous Cretaceous Cretaceous Ichthyosaurs Cretaceous Cretaceous Jurassic- Jurassic— Triassic —

Cretaceous , . Cretaceous Plesiosaurs Cretaceous Cretaceous Cretaceous Permian Triassic Permian Primitive diapsids —Triassic

Jurassic— Triassic Triassic Recent Triassic -Jurassic Rhynchocephalidns Cenozoic Cretaceous Cretaceous Cretaceous Cretaceous Cenozoic Cenozoic Cretaceous Cenozoic Recent -Recent —Recent — Recent — Recent —Recent -Recent —Recent Lizards, snakes —Recent

Cretaceous Cretaceous Cretaceous Cretaceous Cretaceous Cretaceous Mosasaurs

Triassic Triassic Triassic Triassic Triassic Phytosaurs

Triossic Triassic Triassic— Jurassic- , Triassic— Cretaceous Cretaceous Cretaceous Theropod dinosaurs Cretaceous Cretaceous Cretaceous Cretaceous Oetaceous Jurassic — Jurassic- Cretaceous Cretaceous Cretaceous Jurassic Jurassic Sauropod dinosaurs Cretaceous Cretaceous

Jurassic— Jurassic— Jurassic- Cretaceous Cretaceous Ornithopod dinosaurs Cretalc0UJ Cretaceous Cretaceous

Jurassic Jurassic Jurassic Stegosaurian dinosaurs

Cretaceous Ankylosaurian dinosaurs Cretaceous Cretaceous Cretaceous Cretaceous

Cretaceous Ceratopsian dinosaurs Cretaceous

Jurassic — Cretaceous Jurassic Flying reptiles Cretaceous

Cretaceous Cretaceous Triassic — Cretaceous Cenozoic Jurassic Cenozoic Crocodilians — Cenozoic Recent — Recent Cenozoic — Recent —Recent —Cenozoic -Recent

131 that of a detailed nature. Indeed, this is one fossils of these aquatic reptiles are very subject that will never be enclosed or broadly distributed, as might be expected. bounded within a circumscribed horizon Fine ichthyosaurs and plesiosaurs come beyond which the law of diminishing re- from central Europe and southern England, turns will make work impracticable. There from western North America, from Bussia, will always be something new in the world India, Australia, New Zealand, South of fossils, because even in the best known America, and Spitsbergen. Mosasaurs are regions erosion goes on, continually and found especially well preserved in western inexorably, and thus there is a constant and central Europe and in North America, exposure of new materials. particularly in western Kansas. Let us now make a brief survey of the The Triassic thecodont reptiles, of which places in which the dinosaurs and their the most widely known are the phytosaurs, relatives have been found. are found in North America, especially in The greatest and most numerous discov- southwestern United States and along the eries of dinosaurs have been made in west- eastern seaboard, in Scotland, Central ern North America, particularly in Utah, Europe, and South Africa. Wyoming, Colorado, New Mexico, Mon- Of the "mammal-like reptiles," the great tana, and Alberta. Dinosaurs have also been center for the discovery of pelycosaurs is in found in southern England and in France, north central Texas, although these animals Belgium, and Germany. They are also are found additionally in Bussia. The found in Mongolia, and in recent years, in therapsids show a wide distribution, being various Chinese localities. Fragmentary re- especially abundant in South Africa, Bus- mains have been found in India. Some very sia, western China, and Brazil. important materials have come from British The primitive cotylosaurs are found in East Africa, and the presence of these rep- Texas, Bussia, and South Africa.

tiles is indicated in Madagascar. They are The labyrinthodont amphibians, from found also in South America, especially Pa- some of which the reptiles evolved, occur in tagonia, and in Australia. Permian and Triassic beds in Texas and Naturally, the same sediments that have southwestern United States, in England, yielded dinosaurs have also been produc- central Europe, Bussia, India, Greenland, tive of their contemporaries, especially and South Africa. crocodiles and turtles. As for the surviving types of amphibians The flying reptiles are found most and reptiles, these are often found in the abundantly in the Jurassic deposits of cen- same localities and sediments as their extinct tral Europe and southern England, and in relatives. In addition crocodilians, turtles, the Cretaceous chalk beds of Kansas. snakes, lizards, and amphibians are found The aquatic contemporaries of the dino- in various Cenozoic sediments throughout saurs (especially the ichthyosaurs, plesio- the world. They are, however, of so much saurs, and mosasaurs) are found in sedi- less importance from the paleontological ments of marine origin correlative in age viewpoint than the mammals with which with the continental deposits in which the they were contemporaneous that the post- dinosaurs occur. Because marine animals Cretaceous localities will not be listed or are able to roam over vast distances, the discussed here.

132 18 How the Dinosaurs and Their Relatives are Classified and Named

| HREE HUNDRED YEARS AGO mail's knowl- our world, and of such stuff was Lin- a dis- | edge of nature was limited and un- naeus. Linnaeus, who was in his day v organized. People were familiar to some tinguished botanist, conceived the idea of extent with the animals and the plants naming all of the living things on earth— around them, but this familiarity was what the plants and the animals—and this he did we might call an "anecdotal knowledge" of to the limits of his knowledge in his great nature. Men knew in a superficial sort of work, the Systema Naturae, one of the most way something of the habits of the common important publications in the history of the birds and beasts, they had a practical written word. Now this seems simple, yet knowledge of the medicinal herbs, the no man, before the time of Linnaeus had domesticated plants, and the trees. But this had either the vision or the ability to

knowledge was not organized, it was a attempt such a thing. True enough, people hodgepodge of unassorted facts. had names for plants and animals, but they

Then, in the first part of the eighteenth were vernacular names, in Latin or Greek, century, there lived in Sweden a man who or English, or Spanish, or a thousand and was destined to bring order out of chaos, a one other tongues. It was Linnaeus who man who changed the course of thought in had the conception of a logical and sys- the natural sciences from haphazard obser- tematic manner of naming the plants and vations and speculations to a systematic and animals of the world with names that would

integrated plan whereby all of nature took be applicable everywhere and by every- on a new meaning. It was as if a curtain body. had been lifted on the world of nature, So he invented the "binomial system of revealing the life of the earth in orderly nomenclature," which may at first sound aspects which hitherto had been quite un- like a mouthful, but which is in reality a suspected. simple and logical plan for distinguishing The name of this man was Carl von the vast multitude of living things one from Linne, usually known as Linnaeus, one of the other. According to the Linnaean sys- the great figures in the history of science. tem, every distinct type of animal and plant Every now and then in the course of human was to have two names, one known as the events a great man appears, a man who generic name, the other as the trivial takes the labors of his predecessors and of name. The generic name may be compared his fellow men, and shapes them into some- with a human family name such as Smith thing—a method of thinking or a way of or Brown. It denotes a comparatively small life—which has a profound effect upon the group of related forms belonging to a entire course of human history and en- single genus, and, Chinese fashion, it al- deavor for generations afterwards. ways precedes the specific or trivial name. These rare men are the geniuses of The trivial name may be compared with

133 a human given name, such as John or Ordinarily generic and specific names are

Henry or Mary. It denotes a certain species italicized. The generic name is always contained within the genus. These two spelled with the initial letter capitalized; names in the Linnaean system indicate the it is preferable that the initial letter should basic relationships of any particular type not be capitalized in the trivial name. In of animal or plant. Linnaeus used Latin or scientific work it is common to cite the latinized Greek names when he first began name of the author of a genus or species— his tremendous and epochal labor of nam- the name of the person who first described ing all the living things known to him, and the form according to the Linnaean bi- it is still the general practice to use such nomial system, thus: Crotalus adamanteus forms, although by modern authors "bar- Beauvais. But commonly the name of the barous" names are also frequently utilized. author is not cited. In many general dis- The important feature of the Linnaean sys- cussions, only the generic names are used, tem is that it affords a convenient "handle" and such has been the case in much of for designating animals and plants, no mat- this book. ter what may be the nationality and lan- Which brings us to a common complaint guage of the person who may be studying among those who would become ac- a particular form. quainted with fossils. "Why do we have to For instance, the horse in the Linnaean learn so many long-winded and difficult

system of nomenclature is Equus caballus, names?" The answer is that most fossils do

and by this name it is known to scientists not have any other names besides their all over the world, whether they be natives scientific ones. For instance, horses were of France, Russia, China, or Timbuktu. The known to generations of English-speaking

advantage of such a system is at once ob- people before Linnaeus first designated vious when one considers that, while an them scientifically as Equus caballus. But Englishman or an American may speak of most fossils have been made known only

a "horse," this same animal is known to the through the labors of the scientific student

Frenchman as a "cheval," to the Spaniard of life, and so it is that the dinosaurs, the as a "caballo," to the German as a "Pferd," phytosaurs, the pterosaurs, and the host of and so on, almost ad infinitum. other extinct reptiles discussed in this book But even beyond the advantage of mak- have no names other than their scientific

ing animals and plants uniformly distin- ones. Of course it might be possible to

guishable to men everywhere, the Linnaean invent "common" names for all of the dino-

system is valuable in that it expresses the saurs and the other extinct animals that are

relationships of the various forms of life to known to us and are being made known by

one another; it has made of natural history new discoveries every year. But this would a formalized and logical science, rather only introduce complications in the long

than a collection of curious facts. By an run, and would inevitably lead to endless

international agreement, this system dates confusion. For instance, isn't it easier to from the year 1758, when the tenth edition buckle down and learn Triceratops, Proto-

of Linnaeus' Systema Naturae was pub- ceratops, Styracosaurus, and the like, than

lished. That is the official beginning of all to deal with such voluminous circumlocu-

scientific classifications of animal life. tions as "three-horned dinosaur," "ancestral

134 horned dinosaur," "horned dinosaur with Camera = a chamber, sauros = lizard, spikes around the frill," and so on? supremus — highest. "Supreme chambered Moreover, scientific names aren't so diffi- reptile" (in allusion to the structure of the cult if one will look at them carefully, re- vertebrae). fusing to be frightened by their seeming An example of a substantive in apposition length and complexity. The important would be Tyrannosaurus rex: Tyrannos = thing is to analyze each name the first time tyrant, sauros = lizard, rex = king. "King it is seen. If this is done, the name will have of the tyrant dinosaurs." a meaning, and, moreover, it will thereafter An example of a substantive in the geni- be remembered. Perhaps a few remarks as tive, formed in this case by adding "i" to a to the manner in which scientific names are proper name would be Ornitholestes her- formed will be of help in analyzing and manni: Ornithos = bird, testes = robber, learning these names. hermanni = A. Hermann, a famous paleon-

As mentioned above, the generic name is tological preparator. "Bird robber (dino- commonly latinized Greek, or Latin, and as saur) in honor of Adam Hermann." such it may be a simple or a compounded Perhaps this may serve to give some idea single word that expresses some real or of the manner in which zoological names fancied attribute of the animal to which it are composed. Perhaps it is all very con- applies. For instance, the first recognizable fusing, and the reader is certain to become bird, ArcJiaeopteryx, was named by com- completely enraged when he learns that bining two Greek terms, archaios = ancient some whopping big animal is named parvus or old, and pteryx — wing. Thus the com- = small, or some small animal is named bination means "ancient wing," or to trans- grandis = big, owing to original miscon- late more freely, "the ancient winged ceptions on the part of the person who first creature." However, the name may be a described the beasts. "barbarous" word or a combination of Moreover, some of the authors who have barbarous and classic, such as Lambeo- christened strange, new beasts, have, like saurus, from Lambe = Lawrence Lambe, Shakespeare, known "little Latin and less a Canadian paleontologist, and sauros = Greek," so that the names coming from lizard. their non-classic pens have been in some The trivial name, like the generic name, cases etymological monstrosities. And in may be classic or barbarous. It may be an addition, some authors who should know adjective, agreeing with the generic name better have at times been just plain care- grammatically, it may be a substantive in less. The result is that try as we may, names the nominative standing in apposition with sometimes don't work out very well in the generic name, or it may be a substantive translation, nor do they always make much in the genitive, in which case it usually sense. But according to the rules, once a expresses a locality from which the species name is given it must stand, no matter how was first described, or some person in whose inappropriate it may be, otherwise there honor it is named. would be a complete lack of permanence.

For instance, as an example of the adjec- The important thing to remember is that

tival specific name, there is Camerasaurus the name is a name, a tag to identify the supremus: animal, and not a description.

135 The classification of animals and plants, taken as a whole, involves more than just the binomial designations of genera and

species. It is extended to include increasing- ly comprehensive categories; thus genera are combined into families, families are grouped into orders, orders are combined into the higher category of classes, while various classes make up phyla. The arrange- ment may be expressed, from the higher to

the lower categories (or to put it another

way, from the greater to the lesser di- visions) as follows:

Suppose we wish to express the position of a modern reptile, the rattlesnake, by the system of Linnaean Nomenclature.

Kingdom—Animal (animals as opposed to plants) Phylum—Chordata (animals with back- bones)

Class—Reptilia (the reptiles)

Order—Squamata (the lizards, snakes, and their relatives)

Family—Crotalidae (the pit vipers) Genus—Crotalus (rattlesnakes) Species—adamanteus (the dia-

The system under which all animals and mond-back rattler) plants are classified The great primary divisions of the animal PHYLUM SUPERCLASS CLAS! kingdom are the phyla. For instance there is a Phylum Protozoa for all single-celled AGNATHA (Jowliii vartabratat) animals, so many of which are unpleasantly

PLACODERMI known to us as diseases. Then there is a (Cartaln prlmltlva "flthat") PISCES Phylum Porifera for the sponges, a Phylum CHONDRICHTHYES (the shark*) Coelenterata for the corals, a Phylum OSTIICHTHYIS Arthropoda for the insects, spiders, and (Tha bony flthai) _ crustaceans, and so on. All the animals with ~AM»HlalA single (Tha amphibians) backbones are contained within a

RIPTIIIA phylum, known as the Vertebrata or (Tha raptllat) Chordata. This phylum may be subdivided TETRAPODA-< AVIS as shown opposite. (Tha blrdt) MAMMALIA Two classes, Amphibia and Reptilia, (Tha mammalt) especially concern us in this present work.

136 The Main Groups of Amphibians and Reptiles,

and Their Span in Geologic History

J . . . i

CLASS AMPHIBIA *Order Labyrinthodontia— roof-skulled amphibians -:: *Order Lepospondyli— __ — ______:

Order Caudata or Urodela — salamanders — — — —

Order Salientia or Anura — frogs, toads— — — — - Order Apoda— __ — _ — — — _ — — — —

CLASS REPTILIA ubclass Anapsida— no temporal openings

*Order Cotylosauria— primitive reptiles — — — — — —\

Order Chelonia— turtles - — — — — — — ___ — — ubclass Synapsida— lower temporal opening

*Order Pelycosauria— Permian reptiles - — — —

*Order Therapsida— mammal-like reptiles - —- — ubclass Parapsida—upper temporal opening

"Order Mesosauria — ancestors of ichthyosaurs - —

*Order lehthyopterygia — ichthyosaurs — — — — — iubclass Euryapsida— upper temporal opening

*Order Protorosauria — ancestors of plesidsaurs — —

*Order Sauropterygia — plesiosaurs — — — — — —

•ubclass Diapsida —two temporal openings

*Order Eosuchia— primitive diapsids — — _ — — -

Order Rhynchocephalia — persisting as Sphenodon —

*Order Thecodontia— ancestors of dinosaurs— - — —

'Order Saurischia— saurischian dinosaurs — — — —

*Order Ornithischia — ornithischian dinosaurs— — —

*Order Pterosauria— flying reptiles— ___ — — .

Order Crocodilia— crocodiles— — — — — — — —

Order Squamata— lizards, mosasaurs, snakes- — — -

— Extinct SYNOPTIC TABLE OF THE AMPHIBIA AND REPTILIA, INCLUDING THE GENERA MENTIONED IN THIS BOOK

iphibic

ORDER LABYRINTHODONTIA ORDER SALIENTIA (ANURA) (The dominant amphibians of late Paleozoic (The frogs and toads. Triassic-Recent; Europe, and early Mesozoic times. Devonian-Triassic.) North America, Asia, Africa, South America, Suborder Embolomeri Australia.)

(The first labyrinthodonts. Devonian-Permian; Europe, North America.) Genus Ichthyostega ORDER LEPOSPONDYLI (Devonian; Greenland.) (A group of early amphibians. Pennsylvanian- Genus Diplovertebron Permian; Europe, North America.) (Pennsylvanian; Europe.) Genus Diplocaulus Suborder Rhachitomi (Permian; North America.) (The culmination of labyrinthodont development. Pennsylvanian-Permian; Europe, North Amer- ORDER CAUDATA (URODELA) ica.) (The salamanders. Cenozoic-Recent; Europe, Genus Eryops North America, Asia, Africa, South America, (Permian; America.) North Australia.) Suborder Stereospondyli ("Degenerate" labyrinthodonts. Triassic; Europe, North America, Asia, Africa, Australia.) ORDER GYMNOPHIONA Genus Buettneria (Tropical legless amphibians. Recent; Asia, (Triassic; North America.) Africa, South America.)

'lass Reptilia

Subclass Anaps

ORDER COTYLOSAURIA Europe, North America, Africa.) Genus Diadectes (Primitive reptiles. Pennsylvanian-Triassic; (Permian; North America.) Europe, North America, Africa.) Suborder Seymouriamorpha Genus Pariasaurus (Permian; Africa.) (The first reptiles. Pennsylvanian-Permian; Scutosaarus Europe, North America.) Genus Genus Seynxouria (Permian; Europe.) Procolophon (Permian; North America.) Genus Suborder Captorhiuomorpha (Triassic; Africa) Genus Hijpsognathus (Small primitive reptiles. Permian; North Amer- (Triassic; North America.) ica.) Genus Labidosaurus (Permian; Nortli America.) ORDER CHELONIA Suborder Diadectomorpha (Turtles. Permian-Recent; Europe, North Amer- (Primitive reptiles. Pennsylvanian-Triassic; ica, Asia, Africa, South America, Australia.)

138 Suborder Eunotosauria Suborder Pleurodira (Turtle ancestors. Permian; Africa.) (Side-neck turtles. Cretaceous-Recent; Europe, Genus Eunotosaurus North America, Asia, South America, Australia.) (Permian; Africa.) Suborder Cryptodira Suborder Amphichelydia (Vertical-neck turtles. Cretaceous-Recent; Europe, North America, Asia, Africa, South (Primitive turtles. Triassic-Eocene; Europe, America.) North America.) Genus Triassochelys (Triassic; Europe.)

Subclass Synapsida ORDER PELYCOSAURIA Genus Moschops (Permian; Africa.) (Aberrant mammal-like reptiles. Pennsylvanian- Permian; Europe, North America.) Genus Titanosuchus Genus Varanosanrus (Permian; Africa.) (Permian; North America.) Suborder Dicynodontia Genus Ophiacodon (Tusked forms. Permian-Triassic; Europe, North (Permian; North America.) America, Asia, Africa, South America.) Genus Dimetrodon Genus Dicynodon (Permian; North America.) (Permian; Europe, Africa.) Genus Edaphosaurus Genus Stahlekeria (Permian; North America.) (Triassic; South America.) Suborder Theriodontia ORDER THERAPSIDA (True mammal-like reptiles. Permian-Triassic; (Mammal-like reptiles. Permian-Triassic; Europe, Europe, Africa.) North America, Asia, Africa, South America.) Genus Bauria Suborder Dromasauria (Triassic; Africa.) (Primitive types. Permian; Africa.) Genus Cynognathus Suborder Dinocephalia (Triassic; Africa.) (Large, heavy-headed forms. Permian; Europe, Suborder Ictidosauria Africa.) (Transitional to mammals. Triassic; Africa.)

Subclass Parapsida ORDER MESOSAURIA ORDER ICHTHYOSAURIA (Early aquatic reptiles. Pennsylvanian; Africa, (Fishlike reptiles. Triassic-Cretaceous; Europe, South America.) North America, Asia, South America, Australia.) Genus Mesosaurus Genus Ichthyosaurus (Pennsylvanian; Africa.) (Jurassic; Europe.)

Subclass Euryapsida ORDER PROTOROSAURIA ORDER SAUROPTERYGIA (Permian-Jurassic; Ancestral types. Europe, North (Aquatic paddlers. Triassic-Cretaceous; Europe, America, Africa.) North America, Asia, Australia.) Genus Araeoscelis Suborder Nothosauria (Permian; North America.) (Strand dwellers. Triassic; Europe.) Genus Protorosaurus Genus Nothosaurus (Permian; Europe.) (Tn'assic; Europe.)

139 Suborder Plesiosauria Suborder Placodontia (Open-sea paddlers. Triassic-Cretaceous; Europe, (Shallow-water paddlers. Triassic; Europe.) North America, Asia, Australia.) Genus Placodus Genus Plesiosaurus (Triassic; Europe.) (Jurassic; Europe.) Genus PlacocJielys Genus Elasmosaurus (Triassic; Europe.) (Cretaceous; North America.)

Subclass Diapsida

ORDER EOSUCHIA Suborder Theropoda (Primitive diapsids. Permian-Jurassic; Europe, (Bipedal, carnivorous dinosaurs. Triassic-Creta- North America, Africa.) ceous; Europe, North America, Asia, Africa, Genus Youngina South America, Australia.) (Permian; Africa.) Genus Ornitholestes Genus Yaungoides (Jurassic; North America.) (Permian; Africa) Genus Struthiomimus (Cretaceous; North America.) ORDER RHYNCHOCEPHALIA Genus Allosaurus (Small, persisting diapsids. Triassic-Recent; (Jurassic; North America.) Europe, North America, Asia, Africa, South Genus Gorgosaurus America, New Zealand.) (Cretaceous; North America.) Genus Champsosaurus Genus Tyrannosaurus (Cretaceous-Eocene; North America.) (Cretaceous; North America.) Genus Sphenodon Suborder Sauropoda (Recent; New Zealand.) (Giant quadrupedal herbivores. Triassic-Creta- ORDER THECODONTIA ceous; Europe, North America, Asia, Africa, South America, Australia.) (Stem diapsids. Triassic; Europe, North Amer- Genus Plateosaurus ica, Asia, Africa.) (Triassic; Europe, Asia.) Suborder Pseudosuchia Genus Brontosaurus (Ancestral bipedal thecodonts. Triassic; Europe, (Jurassic; North America.) North America, Africa.) Genus Camarasaurus Genus Euparkeria (Jurassic; North America.) (Triassic; Africa.) Genus Diplodocus Genus Ornithosuchus (Jurassic; North America.) (Triassic; Europe.) Genus Cetiosaurus Genus Saltoposuchus (Jurassic; Europe.) (Triassic; Europe.) Genus Brachiosaurus Suborder Phytosauria (Jurassic; North America, Africa.) (Quadrupedal crocodile-like thecodonts. Triassic; Europe, North America, Asia, Africa.) ORDER ORNITHISCHIA Genus Machaeroprosopus (Dinosaurs. Jurassic-Cretaceous; Europe, North America, Asia, Africa, South America.) (Triassic; North America.) Genus Clepsysaurus Suborder Ornithopoda (Triassic; North America.) (Duck-billed dinosaurs. Jurassic-Cretaceous; Genus Rutiodon Europe, North America, Asia, Africa, South America.) (Triassic; North America.) Genus Hypsilophodon ORDER SAURISCHIA (Jurassic; Europe.) (Dinosaurs. Triassic-Cretaceous; Europe, North Genus Camptosaurus America, Asia, Africa, South America, Australia.) (Jurassic-Cretaceous; North America.)

140 Genus Iguanodon Suborder Pterodactyloidea

(Cretaceous; Europe.) (Short tails. Jurassic-Cretaceous; Europe, North Genus Hadrosaurus or Trachodon America, Africa.) (Cretaceous; North America.) Genus Pteranodon Genus Kritosaarus (Cretaceous; North America.) (Cretaceous; North America.) ORDER CROCODILIA Genus Corythosaurus (Crocodiles. Triassic-Recent; Europe, North (Cretaceous; North America.) America, Asia, Africa, South America, Australia.) Genus Lambeosaurus Suborder Protosuchia (Cretaceous; North America.) (Ancestral crocodiles. Triassic; North America.) Genus Parasaurolophns Genus Protosuchus (Cretaceous; North America.) (Triassic; North America.) Genus Troodon Suborder Mesosuchia (Cretaceous; North America.) (Mesozoic crocodiles. Jurassic-Cretaceous; Genus Pachyceplialosaurus Europe, North America, Africa, South America.) (Cretaceous; North America.) Genus Teleosaurus Suborder Stegosauria (Jurassic; Europe.) (Armored dinosaurs. Jurassic; Europe, North Suborder Thalattosuchia America, Africa.) (Marine crocodiles. Jurassic; Europe, North Genus Stegosaurus America, South America.) (Jurassic; North America.) Genus Geosaurus Suborder Ankylosauria (Jurassic; Europe.) (Armored dinosaurs. Cretaceous; Europe, North Genus Metriorhynchus America, South America, Asia.) (Jurassic; Europe.) Genus Ankylosaurus Suborder Eusuchia (Cretaceous; North America.) (Modern crocodiles. Cretaceous-Recent; Europe, Genus Palaeoscincus North America, Asia, Africa, South America, (Cretaceous; North America.) Australia.) Genus Nodosaurus Genus Phobosuchus (Cretaceous; North America.) (Cretaceous; North America.) Suborder Ceratopsia Genus Crocodilus (Horned dinosaurs. Cretaceous; Asia, North (Cenozoic-Recent; Europe, Asia, Africa.) America.) Genus Gavialis Genus Psittacosaurus (Cenozoic-Recent; Asia.) (Cretaceous; Asia.) Genus Alligator Genus Protoceratops . (Cenozoic-Recent; Asia, North America.) (Cretaceous; Asia.) ORDER SQUAMATA Genus Clwsmosaurus (Lizards and snakes. Cretaceous-Recent; Europe, (Cretaceous; North America.) North America, Asia, Africa, South America, Genus Monoclonius Australia.) (Cretaceous; North America.) Suborder Lacertilia Genus Styracosaurus (Lizards. Cretaceous-Recent; Europe, North (Cretaceous; North America.) America, Asia, Africa, South America, Australia.) Genus Triceratops Genus Varanus (Cretaceous; North America.) (Cenozoic-Recent; Asia.) ORDER PTEROSAURIA Genus Mosasaurus (Flying reptiles. Jurassic-Cretaceous; Europe, (Cretaceous; Europe.) North America, Africa.) Genus Tylosaurus Suborder Rhamphorhynchoidea (Cretaceous; North America.) (Long tails. Jurassic; Europe.) Suborder Ophidia Genus Rhamphorhynchus (Snakes. Cretaceous-Recent; Europe, North (Jurassic; Europe.) America, Asia, Africa, South America, Australia.)

141 19 Other Sources of Information

literature on the subject of fossil malian evolution. Some of the figures are out The of date. amphibians and reptiles is considerable the Past. and is confined for the most part to Lucas, Frederic A. Animals of technical papers and monographs published American Museum Handbook Series, 1929. in numerous scientific journals throughout No. 4, 7th Edition, 3rd Printing, A deservedly popular book. It deals with the world. To make a list of only the most selected forms of extinct vertebrates and does "important" of the technical papers on the not pretend to be comprehensive. subject would be to append a bibliography Lull, Richard Swann. Organic Evolu- of such length onto this little book as to tion. Second Edition. New York: Mac- give the reader visions of libraries, cata- millan, 1929. logues, and stacks without end. Therefore A textbook on adaptation in the animal king- only a selected list of general or compre- dom. Portions of it are concerned with certain hensive works will be given for the reader evolutionary lines among the reptiles. who is interested in going further into this Marsh, O. C. The Dinosaurs of North subject of ancient tetrapods. In this con- America. Sixteenth Annual Report, nection, several excellent bibliographies on U. S. Geological Survey, 1896. Pp. 133- fossil vertebrates—mostly by American 244, 84 plates. authors—have been or are in the process of A valuable work, even though somewhat out of date. being published. With these at hand, it is possible to find virtually every paper that Matthew, W. D. Dinosaurs. American! has ever been published on the subject of Museum Handbook Series, No. 5, 1915. vertebrate paleontology. An excellent succinct book on the dinosaurs. Out of print and difficult to obtain. General Works Matthew, W. D. Outline and General Gilmore, Charles W. In Cold Blooded Principles of the History of Life.

Vertebrates. Part II, Chapter I, pages Synopsis of Lectures in Paleontology 1.

161-172 (fossil amphibians); Part III, University of California Syllabus

Chapters I-VI, pages 211-290 (fossil Series, Syllabus No. 213. 1928. reptiles, particularly dinosaurs, swim- A short general textbook of paleontology by a great authority. Parts of it are concerned ming and flying reptiles.) Smithsonian with amphibian and reptilian evolution. Scientific Series, Volume 8. Smithson- Owen, Richard. A History of British Fos- ian Institution Series, Inc. New York, sil Reptilia. Reprinted from publica- 1930. tions of the Palaeontographical Society, A comprehensive and very readable account by an outstanding authority. London. 1849-1884.

Hutchinson, H. N. Extinct Monsters and Romer, Alfred S. Vertebrate Paleontolo-

Creatures of Other Days. London: gy. Chicago: University of Chicago Chapman and Hall, 1910. Press, 1933. An account mainly of reptilian and mam- The most comprehensive modern textbook on

142 the subject. A "must" item for all serious Bibliographies students. Nopcsa, F. Osteologia reptilium fossilium Romer, Alfred S. Man and the Verte- et recentium. Fossilium catalogus, Pars

brates. Third Edition. Chicago: Uni- 27. Berlin. 1926. "Supplement" ibid. versity of Chicago Press, 1941. Pars 50. 1931. semi-popular book, which An excellent of Lists to that date almost every paper of deals fossil amphibians and only a part with importance on fossil amphibians and reptiles. reptiles. Hay, O. P. Bibliography and Catalogue Swinton, W. E. The Dinosaurs. London: of the Fossil Vertebrates of North Thomas Murby and Company, 1934. America. Bulletin U. S. Geological The most recent general text devoted exclu- Survey, 179. 1902. Second Bibliography sively to dinosaurs. Important. and Catalogue of the Fossil Vertebrata Watson, D. M. S. Article "Reptiles" in of North America. Carnegie Institution the Encyclopaedia Britannica, 14th of Washington, Publication No. 390, Edition, Vol. 19, 1928. Pp. 180-200. Vol. I. 1929. Idem, Vol. II. 1930. A concise account with emphasis upon the These publications furnish a complete bibli- fossils. ography of all literature on North American fossil vertebrates from the beginnings of Williston, S. W. American Permian the science on this continent to the year 1928. Vertebrates. Chicago: University of Camp, C. L. and V. L. VanderHoof. Chicago Press, 1911. Bibliography of Fossil Vertebrates. Williston, S. W. Water Reptiles of the 1928-1933. Geological Society of Past and Present. Chicago: University America, Special Papers, No. 27. 1940 of Chicago Press, 1914. Camp, C. L., D. N. Taylor, and S. P.

Williston, S. W. The Osteology of the Welles. Bibliography of Fossil Ver- Reptiles. (Edited by W. K. Gregory) tebrates 1934-1938. Geological Society Cambridge: Harvard University Press, of America, Special Papers, No. 42. 1925. 1942.

Especially valuable for the student of fossil These two papers carry on where Hay left

reptiles. off, and in addition list all of the literature for the rest of the world during the years von ZiTTEL, Karl A. Text-Book of indicated. The series is to be continued. Palaeontology. Vol. II. Second English Romer, Alfred S., Nelda Wright, and edition, revised by A. S. Woodward Tilly Edinger. A bibliography is now from the translation by Charles R. in preparation which will deal with all Eastman. London: Macmillan and of the literature on fossil vertebrates Company, 1932. outside of North America prior to the The standard reference book on fossils. Vol- year 1928. It will be published by the ume II deals with fishes, amphibians, reptiles, and birds. Geological Society of America.

143

Index, Glossary, and Guide to Pronunciation

water and culminates upon Aquatic dinosaurs, specializations

land.), 137 (illust.); diagnostic in, 87 A-, In Greek, a negative prefix characters of, 42; distribution Aquatic reptiles, comparison with meaning "not" or "without" of, 130-132; evolution of, 43, fishes and porpoises, 108-110; Academy of Natural Sciences of 44, 46 (diagr.), 47; in synoptic- evolution of, 104-114; extinc- Philadelphia, fossil collection table, 138; reproduction in, 47 tion of, 117; illustrations of, of, 24 Amphibians, Age of, 39 104, 109; in svnoptic table, Adaptations in the heads of Amphichelydia (am-fi-kel-m-e-ya. 139; kinds of, 104; Niobrara homed dinosaurs, 82 (illust); From Greek, amplii— "on both formation, 113, 114; reproduc- in teeth and jaws of dinosaurs, sides" + chelys— "tortoise," in tion in, 108; tails of, 107 (il- 88; in the vertebrae of Bron- reference to the relationships lust.); Tylosaurus, 112 (illust.); tosaurus, 84; to large size, 84, of these primitive turtles.), 123 where found, 132 85 (illust.); in synoptic table, 139 Araeoscelis (air-e-oss-seel-is. From Agamids, 122 Anapsida (an— APS-i-da. From Greek, araios— "thin" + skelis "Age of Amphibians," in the ge- Greek, an—"without" + apsides —"leg."), 110; in svnoptic table, ologic time scale, 39 —"an arch." Reptiles without 139 "Age of Dinosaurs," 36, 37, 38 temporal openings in the Archaeoptenjx (ar-kee-op-ter-ix. (diagr.), 39 skull.), 48, 50, 51, 123; in From Greek, archaios— "an- Age of the earth, 36, 37, 38 synoptic table, 138, 139; skull cient" + pteryx—"wing."), 67 (diagr.) of, 49 (illust.); span in geologic (illust.), 103 (illust.), 135; de- "Age of Mammals," 38 (diagr.) history, 137 (illust.) scription of, 102

"Age of Man," 36, 37, 38, 39 Ancestors of the dinosaurs, 60 Armored dinosaurs, 78 (illust.); (diagrs.) Ancestry of turtles, 123 description of, 77-79; eating "Age of Reptiles," 36, 37, 39 Animals of the Past, by Frederic mechanism of, 88; in synoptic Agnatha (ag-NATH-a. From Greek, A. Lucas, 7 table, 141; means of defense,

a—"without"-\-gnathos—"jaws." Ankylosauria (an-kyle-o-SAWR-e- 91; Palaeoscincus, 78 (illust.), The jawless vertebrates.), 136 ya), 78, 79; in synoptic table, 95, 96; Stegosaurus, 77 (illust.), Alligator (AL-li-gay-tor. From 141 94, 95

Spanish, el lagarto—'ihe liz- Anklyosaurus (an-kyle-o-SAWR-us. Artists, scientific, 33 (illust.), 35 ard."), 120, 121; in synoptic From Greek, ankylos—"curved" Aves (AH-vees. From Latin, aves table, 141 + sauros—"lizard," because of [plural]—"birds"). See Rirds Allosaurus (al-lo-SAWR-us. From the strongly curved ribs.), de- Greek, alios—"other" + sauros scription of, 79; distribution of, B —"lizard"; so named because 131; familv relationships of,

"this genus may be distin- 66 (illust.); in synoptic table, Bad lands, 31 (illusts.) guished from any known dino- 141 Bat wing, 100 (illust.) saurs by the vetrebrae."), 68, Aiming, Mary, 17 Bauria (BowR-e-ya. Named in 69 (illust.), 85, 94, 95; in syn- Anning, Richard, 17 honor of Dr. George Baur optic table, 140; jaws of, 88 Anura (a-NUR-a. From Greek, an [1859-1898], an American pale- (illust.) —"without" + oura—"tail." The ontologist.), 58; in synoptic American Museum of Natural frogs and toads, which have table, 139

History, 15, 21, 23, 24, 51 no tails.), family relationships Belly River age dinosaurs, 95, 96 Amherst College, 18; Museum of, of, 46 (diagr.); in synoptic Berkeley, University of Califor- 24 table, 138; span in geologic nia, 23, 24 Amnion, function of, 47 history, 137 (illust.) Bibliography, 142, 143 Amniote egg, 47, 48 (illust.) Apoda (a-POAD-a. From Greek, a Binomial system of nomenclature, Amphibia (am-FiB-e-ya. From —"without" + podos—"feet." as originated bv Linnaeus, 133- Greek, amphibios—"leading a The tropical, legless amphibi- 136 double life"; in allusion to the ans.), 42; family relationships Birds, 101: ancestry of, 100;

life history of the amphibia, of, 46 (diagr.); span in geologic Archaeoptenjx, 67 (illust.);

which usually begins in the historv, 137 (illust.) birds of Cretaceous period,

145 102; body temperature of, 101; Ceratopsia (ser-a-TOPS-e-ya. From brain of, 101; characteristics of, Greek, keras, keratos—"horn" 100, 101; compared with ptero- Caimans, modem crocodilians, + ops—"face." The horned saurs, 101; evolution of, 52 121 dinosaurs.), 79-83; ancestry of, (Must.), 100 (must.), 101, 102, California Institute of Technol- 80; eating mechanism of, 88; 103 (Must); feathers of, 101; ogy, Pasadena, 24 family relationships of, 66 hind limbs of, 101; modernized Camarasaurus (kam-ar-a-SAWR-us. (diagr.); in synoptic table, 141; in Cenozoic, 102; nest build- From Latin and Greek, camera phylogeny of, 82 (Must.); time ing, 101, 102; wing of, 100 —"a chamber" + sauros—"liz- and distribution of, 131 (table) (Must.) ard," in allusion to die struc- Cetiosaurus (seet-ee-o-sAWR-us. Boas, 122 ture of the vertebrae.), 72; in From Greek, keteios—"ot sea Bogert, Charles M., 7 synoptic table, 140 monsters, or monstrous" + Boids, 122 Camarasaurus supremus, deriva- sauros—"lizard."), 72; in synop- Boltinoff, Henry, cartoon by, 13 tion of name, 135 tic table, 140 Bone Cabin Quarry, Wyoming, Cambrian period, first vertebrates Chameleons, 122 122 in, 41 Champsosaurus (camp-so-SAWR- Boneheaded dinosaur, Pachyceph- Cameron, Arizona, 118 us. From Greek, cJiampsa—'a. alosaurus, 90 (Must.) Camp, Charles L., 23 crocodile" + sauros—"lizard"; a Bone structure of dinosaurs, 84, Camptosaurs, 75; eating mecha- name based on die appearance

85 nism of, 88 of the animal, not upon its re- Bony armor, 27 (Must.) Camptosaurus (kamp-to-SAWR-us. lationships.), description of, Books on dinosaurs, 142, 143 From Greek, kamptos—"bent" 121 (Must.), 122; in synoptic

Brachiosaurus (brak-e-o-SAWR-us. + sauros—"lizard."), . 74 table, 140 From Greek, brachion—"arm" (Must.); description of, 75; in Chasmosaurus (kas-mo-SAWR-us.

-f- sauros— "lizard"; so named synoptic table, 140; time and From Greek, chasma—"open-

because of die great size of the distribution of, 94, 95 ing" -f- sauros—"lizard"; so bones in the forearm.), 86 Canada, National Museum of, 22, named because of openings in (Must.); breathing of, 87; de- 24 the "frill" of this horned dino- scription of, 72, 73; in synoptic Captorhinomorpha (kap-to-RiNE- saur.), description of, 82 table, 140; nasal passage of, 86 o-morf-a. From Greek, kapto- (Must.), 83; in synoptic table, (Must.) "to gulp or eat quickly" + 141

Brain, of birds, 101; of dinosaurs, rhinos—"beak" -f- tnorpha— Chelonia (kel-owN-e-ya. From 92 (Must.), 93; of flying rep- "resemblance." Reptiles related Greek, chelone— "tortoise."), tiles, 99 to Captorhinus, so named be- 123; in synoptic table, 138, Breadiing mechanisms of dino- cause of the structure of the 139; span in geologic history, saurs, 86 (Must.), 87 jaw.), 50; in synoptic table, 138 137 (Must.) Breger, Irv, cartoon by, 12 Carapace, upper shell of turtles, Chicago Natural History Mu- British Museum (Natural His- 124 seum, 22, 24 tory), 17, 23 Carnegie, Andrew, 22 Chicago, University of, 23 Brontosaurus (bront-o-SAWH-us. Carnegie Museum, Pittsburgh, Chicago, Walker Museum of the From Greek, brontos—"thun- 22, 24 University, 23, 24

der" -+- sauros—"lizard."), 22, Carnivorous dinosaurs, adapta- Chinese paleontologists, 23 71 (Must.), 84, 85; adaptations tions in feeding, 87-89; distri- Chondrichdiyes (kon-drik-THi- in vertebrae, 84; adaptations to bution of, 94-96; kinds and ees. From Greek, chondros— large size, 84; description of, activities of, 87-89 "cartilage" + ichthys—"fish." 72, 73; distribution of, 94, 95; Cartoons, 12, 13 The cartilaginous fishes.), 136 habits of, 87; in synoptic table, Case, Ermine C, 23 Chordata (kor-DA-ta. From Latin, 140; neckbone of, 85 (Must.) Caudata (kaud-A-ta. From Latin, chordatus—"having a [spinal] Broom, Robert, 23 caudatus [sing.]—"a tail." The cord."), classification of, 136 Brown, Barnum, 21, 22 tailed amphibians, salaman- Chungking, China, 23 Buettneria (bwet-NER-e-ya. ders.), in synoptic table, 138; Classification by Linnaean sys- Named in honor of W. H. span in geologic history, 137 tem, 133-136' Buettner, paleontological pre- (Must.) Classification of dinosaurs, 68, parator at die University of Cenozoic birds, 102, 103 138-141 Michigan.), 44 (Must.); in syn- Central Asiatic Expeditions of the Clepsysaurus (klep-se-SAWR-us. optic table, 138 American Museum of Natural From Greek, klepsydra—"a. Burrows, fossilized, 30 History, 25 water clock or hourglass" +

146 sauros— "lizard"; so named be- of, 119; in synoptic table, 141; "two" or "double" cause the vertebrae are shaped Jurassic deployment of, 119; Diadcctes (dye-a-DEKT-eez. From like an hourglass.), in synoptic marine, characteristics of, 114; Greek, dm—"across" + dektes— table, 140 Mesozoic radiation of, 120; "bitter"; so named because of Coecilia (see-siL-ee-ya), 42, 44, parallel development with phy- the transversely broad teeth.), 45 tosaurs, 62, 63; span in geo- description of, 50 (illust.), 51; Colbert, Margaret M., illustra- logic history, 119, 137 (illust.) in synoptic table, 138 tions by, 104 Crocodilia, in synoptic table, 141 Diadectomorpha (dve-a-DEKT-o- Colorado Museum of Natural Crocodilians, family relationships morf-a. From Greek, diadectes History, Denver, 24 of, 52 (illust.); in synoptic [see which] + morpha—"form Constrictors (snakes), 122 table, 141; time and distribu- or shape." Animals related to Continental drift, theory of in tion of, 131 (table), 137 Diadectes.), 50, 51; in synoptic

paleogeography, 129 (illust.) table, 138 Convergence in evolution, 108 Crocodilus (krok-o-DiLE-us. From Diapsida (di-APS-i-da. From Conybeare, English paleontolo- Greek, krokodeilos—"croc- Greek, di—"two" + apsides— gist, 114 odile."), 120; in synoptic table, "arches." Reptiles with two Cope, Edward Drinker, Ameri- 141 temporal openings in the can paleontologist, 19 (por- Crossopterygia (kross-op-ter-ij-e- skull.), classification of, 49; in trait), 20-22, 25 ya. From Greek, krossoi—"tas- synoptic table, 140, 141; span Copernicus, 126 sels or fringe" + pteryx—"wing in geologic history, 137 (illust.) Corythosaurus (kor-ith-o-SAWR-us. or fin." Fishes with tasseled or Diapsids, evolution of, 60-63,

From Greek, korythos—"hel- fringed fins.), family relation- 118-124; kinds of, 118-124; met" + sauros—"lizard"; so ships of, 46 (illust.) skull of, 49 (illust.) named in reference to the Crossopterygian fishes, descrip- Diatryma (dye-a-TRY-ma. From helmet-like crest on the skull.), tion of, 41 (illust.), 42 Greek, dia—"through" + tryma 76 (illust), 78 (illust); breath- Cryptodira (krip-to-DiRE-a. From —"a hole," referring to the ing mechanism of, 87; in Cre- Greek, kryptos—"hidden" 4- large openings or foramina that taceous period, 95, 96; in deira—"neck." The turtles in penetrate some of the foot

synoptic table, 141; time and which the neck is withdrawn bones.), 102, 103 (illust.)

distribution of, 95, 96 into the shell vertically and is Dicynodon (dye-siNE-o-don. Cotylosauria (ko-TiLE-o-SAWR-e- thereby hidden.), 123 (illust.); From Greek, di—"two" + kyon, ya. From Greek, kotyles—"cup" description of, 124; in synoptic kynos—"dog" -f odous, odon— + sauros—"lizard"; so named table, 139 "tooth," referring to two dog- because of the shape of the Cuvier, Baron Georges, 15, 16 like teeth in the front of the vertebral articulations, like (portrait), 18, 75 jaws.), 54 (illust.), 56, 57; in little cups.), competition with Cynognathus (sine-og-NATH-us. synoptic table, 139 other vertebrates, 53; evolution From Greek, kyon, kynos— Dicynodontia (dye-siNE-o-dont-e-

of, 50; extinction of, 51; family "dog" -f- gnathus—"jaws"; so ya), 56; in synoptic table, 139 relationships of, 52 (illust.); in named because of the form of Dicynodonts, 56, 57 synoptic table, 138; kinds of, the jaws.), description of, 54 Diet of dinosaurs, 88 50, 51; time and distribution (illust), 58, 59 (illust.); in evo- Dimetrodon (dye-MET-ro-don. of, 131 (table), 132, 137 lution of aquatic reptiles, 54; From Greek, di—"two or (illust.) in synoptic table, 139 double" + metron—"measure" Cotylosaurs. See Cotylosauria + odous, odon—"tooth," refer- Crests in trachodont dinosaurs, D ring to two sizes of teeth in the function of, 87 jaw.), 55, 56; in synoptic table, Cretaceous birds, 102 Darwin, Charles R., 16 (portrait), 139 Cretaceous dinosaurs, kinds and 18, 126 Dinocephalia (dye-no-sef-A-lee- activities of, 95, 96 Decline of the dinosaurs, 115 ya. From Greek, deinos— "ter-

Cretaceous ichthyosaur, 107 Defense, weapons for among rible" -\- kephalon—"head."), (illust.) dinosaurs, 90-92 56-58; in synoptic table, 139 Cretaceous period in North Dental battery of hadrosaurian Dinosaur (DiNE-o-sawr. From America, description of, 95 dinosaurs, 88 Greek, deinos—"terrible" + Crocodiles, ancestor of, 118, 119 Denver, Colorado Museum of sauros—"lizard.") (illust.), 120; description of, Natural History, 24 Dinosauria, as originated by Sir 119; distribution of, 120, 132; Devonian fishes, 41 Richard Owen, 17; derivation evolution of, 118-121; habits Di-, Greek, Latin prefix meaning of name, 64

147 Dinosaurs, by W. D. Matthew, 7 anism of, 88; evolution of, 73- front of the eyes.), 43, 44 Dinosaurs, adaptations of, 84-93; 76; heads of, 76 (illust); in (illust.); in synoptic table, 138 "Age of Dinosaurs," 37, 38 synoptic table, 141; time and Eu-, from Greek, a prefix meaning (illust.); ancestors of, 60-63; distribution of, 95, 96; Tracho- "true" or "right" beginnings of, 60; definition of, don, 74 (illust.) Eunotosauria, in synoptic table, 14; description of, 14; distribu- Dvche Museum of the University 139 tion of, 127-132; family tree of, of Kansas, 24 Eunotosaurus (voo-NOTE-o-sawr- 66 (diagr.); illustrations of, 74, us. From Greek, eu— "right" + 76-79, 81, 82; in synoptic table, notos—"south" -|- sauros—"liz-

140, 141; kinds of, 64-83; phy- ard"; so named because it was logeny of, 66 (diagr.); popular Earliest crocodile, 118 found in South Africa.). 123

ideas about, 11-13; size of, 65; Earth, age of, 36, 37, 38 (illust.), (illust.), 124; in svnoptic table, span in geologic history, 137 40 (illust.); theories of paleo- 139

(illust.); specializations in, 84- geography, 128, 129 Euparkeria (yoo-park-EH-e-ya. 93; structure and relationships Eating mechanism of dinosaurs, Named in honor of Professor of, 67 (illust.); two reptilian 87, 88 (illust.), 89, 90 W. Kitchen Parker [1823- orders represented by, 64, 65, Ecological relationships of dino- 1890], English morphologist 67 saurs, 94-96; "balance of na- and naturalist), 61; in svnoptic "Dinosaur, The," a poem by Bert ture," 84 table, 140 Leston Taylor, 78 Edaphosaurus (e-DAF-o-sawr-us. Euryapsida (your-e-APS-e-da. Diplocaulus (dip-lo-KAWL-us. From Greek, edaplios—"foun- From Greek, euru—"broad" + From Greek, diploos—"double" dation or base" + sauros— apsides—"arches." Reptiles + kaulos—"shaft or stalk," in "lizard."), 54 (illust), 55 with very broad arches below reference to the structure of (illust); description of, 56; in the upper temporal opening.), the vertebrae.), 44, 45 (illust.); synoptic table, 139 49, 104; ancestry and evolution in synoptic table, 138 Egg, amniote, development of, of, 110-112; classification of, Diplodocus (dip-LAH-do-cus. 47, 48 49; in synoptic table, 139, 140; From Greek, diploos—"double" Eggs of dinosaurs, fossilized, 28 skull of, 49 (diagr.) + dokos—"beam"; so named (illust.), 81 Eusuchia (yoo-sooK-e-ya. From because of the double, or bifid, Elasmosaurus (e-LAZ-mo-sawr-us. Greek, eu—"right" + souchos— spines on the vertebrae.), de- From Greek, elasmos—"a thin "crocodile." The true crocodiles

scription of, 72, 73; distribu- plate" -+- sauros— "lizard"; so of modern times.), 120; in syn- tion of, 94, 95; in synoptic- named because of the platelike optic table, 141 table, 140; method of breath- bones of die pectoral and pel- Evolution, of amphibians, 43-47; ing, 87 vic girdles.), 109 (illust.); in of aquatic reptiles, 104-114; of Diplos, from Greek, diploos— synoptic table, 140 birds, 103 (illust.); convergent "double" Embolomeri (em-bol-o-mer-ee. evolution among aquatic rep- Diplovertebron (dip-lo-VERT-e- From Greek, embolos—"thrown tiles, 108; evolution of croco-

bron. From Greek and Latin, in" -|- mews—"part," in refer- diles, 118-121; of diapsid rep- diploos—"double" + vertebron, ence to the complete develop- tiles, 118-124; of dinosaurs, seemingly from vertebra or ment or intercalation of extra 64-83; of eusuchians, 120; of vertebratus. An allusion to elements, the intercentra in the euryapsids, 110-112; of flving vertebral structure.), 44 vertebral column.), 43; in syn- vertebrates, 97-103; of flving

(illust.); in synoptic table, 138 optic table, 138 reptiles, 97-100; of ichthyo- Disappearance of dinosaurs, 38 Environmental changes during saurs, 105-110; of labvrintho- (diagr.), 39 transition from Cretaceous to donts, 43, 44; of lizards, 122, Discovery of fossils, 25-35 Eocene, 117 123; of marine reptiles, 104- Djadoehta, beds of Mongolia, 80 Eosuchia (ee-o-sooK-e-ya. From 114; of mesosaurs, 105; of

Dove, Leonard, cartoon by, 12 Greek, eos—"the dawn" -f- mesosuchians, 119, 120; of Doyle, A. Conan, The Lost souchos—"crocodile." A group mosasaurs, 112-114; over-spe- World, 13 of primitive diapsid reptiles.), cialization in evolution, 115; Dromasauria (drom-a-SAWR-e-ya. 138 (illust.); in synoptic table, parallelism in, 62, 63; evolution From Greek, dromas—"run- 140 of plesiosaurs, 110-112; racial ning" + sauros— "lizard.", 56; Equus caballus, 134 senescence in evolution, 115; in synoptic table, 139 En/ops (ER-ee-ops. From Greek, evolution of reptiles, 47-52, 52 Duck-billed dinosaurs, 74 (illust.), enjein— "to draw out" + ops— (illust.); of rhynchocephalians,

76 (illust.), 95, 96; defensive "face"; so named because the 121, 122; ..I sea-lizards, 112-

weapons of, 90; eating mech- greater part of the skull is in 114; of serpents, 104-114; of 148 snakes, 122, 123; of synapsids, study of fossils, 8, 33-35, 125, Gymnophiona (jim-no-fee-o-na. 53-59; of turtles, 123 (Must), 126; various kinds of fossils, From Greek, gymnos—"naked" 124 26-29 (Musts.); what is a fos- + ophis—"serpent." Actually a Evolutionary concept, importance sil?, 30 group of small tropical amphib- of, 126 Foulke, W. Parker, 18 ians, so named because they Excavation of fossils, 32 (illusts.) Four-footed dinosaurs, develop- have the appearance of scale- Exhibition of fossils, 35 ment of, 65-68, 67 (Must.) less snakes.), 42, 45; in syn- Extinction of dinosaurs, 38 Frogs and toads, distribution of, optic table, 138 (diagr.), 39, 115-117 131 (table); family relation- ships of, 46 (Must.); in synoptic table, 138; span in geologic H

history, 137 (Must); specializa- Haddonfield, New Jersey, 18 Falkenbach, Otto, 21 tions in, 45 Hadrosaurians, aquatic dinosaurs, Family tree of dinosaurs, 66 specializations in, 87 (Must.) Hadrosaurs, dental battery of, Family tree of reptiles, 52 88; duck-billed dinosaurs, 75, (Must.) Gavialis (gave-e-AL-is. From 76 Fenestra, skull opening, 60, 61 Hindu, ghariyal—"a crocodile." Hadrosaurus (had-ro-SAWR-us. Field Museum of Chicago (now When the name was first pub- From Greek, [hjadros—"bulky" Chicago Natural History Mu- lished, the author intended it + sauros—"lizard."), 20, 24, seum), 22, 24 to be Garialis, but the "r" was 76; (Trachodon) in synoptic First land animals, 41 mistaken for a "v" by the prin- table, 141 First land vertebrates, 38 (diagr.) ter. The misspelled word be- Hahn, Frederick L., 7 First pattern of vertebrate flight, came established, and so it Harvard University, Museum of 99 stands. No amount of correc- Comparative Zoology, 23, 24 First reptiles, 38 (diagr.), 48 tion will ever change it, for Hayes, William, cartoon by, 13 First vertebrates, 41 usage is a powerful force in Herbivorous dinosaurs, adapta- Fishes, comparison of with language.), 120; in synoptic tions in feeding, 88, 89; kinds aquatic reptiles and porpoises, table, 141 and activities of, 94-96 108-110; evolution of, 42; Geckos, 122 Hermann, 21, 135 transition of fishes to amphi- Adam, General works, 142 bians, 42 Hesperornis (hes-per-ORN-is. Generic name in die Linnaean [hjesperos—"west- Flight, development of in verte- From Greek, system of nomenclature, 133- "bird."), 102, brates, 97-103 ern" -f- ornis— 136 Flightless birds of early Cenozoic, 103 (Must.) Genus, in Lin- 102 as a division the Heterocercal tail, 108, 114 naean classification, 133-136 Flying reptiles, 97-100, 98 (Must); Hilton, Ned, cartoon by, 13 Geologic time scale, 36-40 distribution of, 131, 132; in Hitchcock, Edward, 18 (illusts.) synoptic table, 141; span in Hofmann, Dr., French Army sur- Geosaurs (jEE-o-sawrs), geologic history, 137 (Must.); 114, 120 geon, 114 wing of pterosaur, 100 (Must.) Geosaurus (jee-o-SAWR-us. From Horned dinosaurs, adaptations in Footprint of dinosaur, fossilized, Greek, ge—"the earth" + heads of, 82 (Must.); descrip- 29 (Must.) sauros—"lizard."), in synoptic tion of, 79-83; eating mecha- table, Fossil collecting, future of, 23 141 nism of, 88; illustrations of, 79, Fossilization, conditions tor, 129, Germann, John C, 7 81, 82; in synoptic table, 141; 130 Giantism in dinosaurs, 92, 93, methods of defense, 91, 92; Fossilized burrows, 30 116 Monoclonius, 95, 96; Protocera- Fossilized insect nests, 30 Gilmore, Charles W., 22 tops, 79 (Must.); Styracosaurus, Fossils, age of oldest, 38 (diagr.); Goddin, Dr., 114 95, 96; Triceratops, 81 (Must.) collections in museums, 21-24; Gondwana land, 128 Hunting dinosaurs, 25-35 (illusts.) conditions for preservation of, Gorgosaurus (gor-go-SAWH-us. Huxley, Thomas Henry, 18, 21 129, 130; economic importance From Greek, gorgos—"terrible" Hypsilophodon (hips-i-LOF-o-don.

of, 125; how they are found, -f- sauros—"lizard."), 70, 95, From Greek, [h]ypsi—"high" removed, and shipped, 25-32 96; in synoptic table, 140 -+- lophos—"crest" + odous, (illusts.); how they are pre- Granger, Walter, 21 odon—"tooth"; so named be-

pared, restored, and exhibited, Gregory, William King, 6, 7, 80 cause of the high-crested 30-35 (illusts.); publication of Growth of dinosaurs, causes of, teeth.), 87; in synoptic table, findings, 34, 35; the scientific 93 140 149

I Hypsognathus (hips-og-NATH-us. Ilia, 85 Lambeosaurus (lamb-e-o-SAWR- From Greek, [h]ypso—"high" Insect nests, fossilized, 30 us. Named in honor of Law- + gnathos—"jaw."), 51; in syn- Intercommunications between rence Lambe [1863-1919], Ca- optic table, 138 continents during Permian and nadian paleontologist, + sauros Mesozoic, 129 -"lizard."), 76 (illust); breath- ing mechanism of, 87; in syn- optic table, 141 J Land animals, first, 38 (diagr.), Ichthyopterygia (ik-thee-op-ter-ij- Jaws of dinosaurs, 89, 90 42 e-ya. From Greek, ichthys— 41, Jesup, Morris K., 21 Land masses, distribution of in "fish" + pteryx—"fin." Reptiles Jurassic dinosaurs, kinds and ac- past, theories of, 128, 129 with fishlike fins.), 105-110; tivities of, 94, 95 Lang, Charles, 21 span in geologic history, 137 Jurassic Period in North America, (illust.) Leidy, Joseph, 18, 19 (portrai*), description of, 94 21 Ichthyosauria (ik-thee-o-SAWB-e- 20, Lepospondyli (lep-o-spoN-dil-ee. ya. From Greek, ichthys— "fish" From Greek, lepos—"& husk + sauros—"lizard."), 105-110; K or scale" in synoptic table, 139 + spondylos— "verte- Kansas, Niobrara Cretaceous beds bra"; so named because of the Ichthyosaurs, 27 (illust.), 104 of, 23 structure of the vertebrae.), (illust.); comparison with fishes 137 Kansas, University of, 23 and porpoises, 108-110; com- (illust.); evolution of, 44, 45; Karroo desert, South Africa, 23 family relationships of, 46 parison with plesiosaurs, 111; "King of the dinosaurs," Tyranno- (illust.); in synoptic table, 138 description of, 105-108; earli- saurus, description of, 70 Linnaean system of nomencla- est, 105; evolution of, 105-110; Knight, Charles R., 7 ture, 133-136 (illust.) family relationships of, 52 Kritosaurus (kritt-o-SAWR-us. Linnaeus, Carl von, 16 (portrait); (illust.); reproduction in, 108; From Greek, kritos—"chosen or his system of nomenclature, tails of, 107 (illust), 108; excellent" sauros—"lizard."), + 133, 134 time and distribution of, 105, 76 (illust.); in synoptic table, Linne. Linnaeus 131, 132, 137 (illust.) See 141 Lizards, description of, 122; evo- Ichthyosaurus, 17, 105 (illust.); family in synoptic table, 139 lution of, 122, 123; re- lationships of, (illust.); in Ichthyostega (ik-thee-o-STEEC-a. 52 synoptic table, 141; kinds of, From Greek, ichthys—"fish" + Labidosaurus (lab-i-do-SAWR-us. sea-lizards stega—"roof"; so 122; monitors, 113; named be- From Greek, lahis, labidos— cause (mosasaurs), 112 (illust.), 113; these primitive amphib- "forceps" + sauros—"lizard"; ians time and distribution of, 131 bridge the gap between so named because the jaws are (table), (illust.); varanids, the fishes 137 and the Stegoce- like forceps.), 50 (illust.); in 113 phalia or "roof-skulled" am- synoptic table, 138 Lobe-finned fishes, 41 (illust.), 42 phibians.), 43, 44; in synoptic Labyrinthodontia (lab-i-RiNTH-o- Localities, important, where pre- table, 138 dont-e-ya. From Greek laby- historic amphibians arid rep- Ichthys, from Greek, ichthys— rinthos—"a labyrinth" + odous, tiles have been discovered, 130 "fish" odontos—"tooth"; so named be- (map) Ictidosauria (ik-ti-do-SAWR-e-ya. cause the internal structure of Location of fossils, 31, 32 From Greek, iktideos—"o{ a the teeth is very complex- Lost World, The, Sir Arthur weasel" -4- sauros—"lizard." labyrinthine. A group of early Conan Doyle, 13 Small, active reptiles, closely amphibians, often called Stego- Lowland dinosaurs, 87 related to the mammals.), in cephalia, stegos—"roof" + Lucas, Frederic A., Animals of synoptic table, 139 kephalon—"skull."), evolution the Past, 7 Iguanids, 122 of, 43 (chart), 44; extinction of, Lyell, Charles, 75 Iguanodon (i-cwAN-o-don. From 47, 48; family relationships of, Regis (England), 17 Spanish and Greek, iguana, 46 (illust.); time and distribu- Lyme from the Haitian igoana—"a tion of, 131 (table), 132, 137 lizard" -f acinus, oclon— (illust.); in synoptic table, 138 M "tooth"; so named because the Lacertilia (la-ser-TiL-e-ya. From teeth resemble those of the Latin, lacertus—"i\ lizard."), in Men .haeroprosopus (mack-ear-o-

iguana.), 17, 75; in synoptic synoptic table, 141 pro-so-pus. From Greek, ma- table, 141 Lambe, Lawrence, 135 chaira—"sword" + prosoupos—

150 "bordering on"; in reference to Mesozoic era, 14, 25, 37, 39 Museum of Comparative Zoology the sharp crest forming the Metriorhynchus (met-ree-o-RiNK- at Harvard University, 23, 24 upper surface of the snout or us. From Greek, metrios— Museum of Paleontology of the rostrum.), 63 (illust); in synop- "moderate" + rynchos— University of California, Ber- tic table, 140 "snout"; so named because the keley, 23, 24 Mammalia (mam-MAiL-e-ya. skull is not excessively long.), Museum of the University of From New Latin, mamma— 120; in synoptic table, 141 Michigan, 23, 24 "the breast," mammalis— "of Meuse River, first fossil of Mosa- Museums, fossil collections in, the breast." The mammals saurns discovered at, 114 21-24 suckle their young. This name Michigan, Museum of the Uni- was coined by Linnaeus, after versity, 23 N analogy with animalis— "ani- Miller, Paul, 23 mal."), 56 Misconceptions about dinosaurs, Names of animals, how given, Mammal-like reptiles, 53; begin- 12, 13 133-136 nings of, 56; extinction of, 59; "Missing link," from cold-blooded National Museum of Canada, Ot- in synoptic table, 139; span in reptiles to warm-blooded mam- tawa, 22, 24 geologic history, 131, 137 mals, 58, 59 Nectridia (neck-TRiD-e-ya. From

(illust.); where found, 132 Mississippian period, 39 Greek, metres, fern, of nectes Mammals, Age of, 38 (diagr.); Modern bird, 103 (illust.) —"a swimmer."), 44 descendants of reptiles, 59; Monaco, Louis A., 7 Nervous system of dinosaurs, 92 family relationships of, 52 Monitors, 113, 122 (illust.), 93

(illust.) Monoclonius (mon-o-KLON-e-us. New Haven, Connecticut, 23 Man, Age of, 36-38, 39 (diagr.) From Greek, monoklonos—"with Niobrara (Cretaceous) beds in Man, not contemporaneous with a single stem"; so named be- Kansas, 23 dinosaurs, 12 cause of the single large horn Nodosaurus (node-o-SAWR-us. Mantell, Gideon, 15, 17, 18, 75 on the skull.), description of, From Greek, nodos—"toothless" Marine crocodiles, 104, 114, 120 83; head of, 82 (illust.); in syn- + sauros— "lizard."), 27 Marine reptiles, evolution of, 104- optic table, 141; kinds and ac- (illust.), 79, 91; in synoptic 114; extinction of, 117 tivities of, 94, 95; time and table, 141 Marine turtles, comparison of distribution of, 95, 96 Nomenclature, binomial system with plesiosaurs, 111 Morrison age dinosaurs, 94, 95 of, as originated by Linnaeus, Marsh, Othniel Charles, 19 (por- Mosasauria (mose-a-SAWR-e-ya. 133-136 trait), 20-22, 25 From Latin and Greek, Mosa— North America, description of in Matthew, William Diller, 7, 21, the Meuse River in Belgium, Cretaceous times, 94; descrip-

126 where the first specimen to be tion of in Jurassic times, 94 Mechanics of biting in dinosaurs, named was found + sauros— North Atlantis, 128 88, 89 (diagrs.) "lizard.") Nothosauria (noth-o-SAWR-e-ya. nothos—"spuri- Merriam, J. C, 23 Mosasaurs, 104, 114, 122; ances- From Greek, Mesosauria (mes-o-SAWR-e-ya. try of, 113; description of, 112- ous" + sauros—"lizard."), 109 From Greek, mesos—"middle" 114; in synoptic table, 141; (illust.), 110; in synoptic table, + sauros—"lizard."), anatom- family relationships of, 113; 139 ical characters of, 105; ances- span in geologic history, 137 Nothosaurus, 109 (illust.); in syn-

tral to ichthyosaurs, 105; de- (illust.); time and distribution optic table, 139

scended from cotylosaurs, 105; of, 131 (illust.), 132; Tylosaur- in synoptic table, 139; span in us, 112 (illust.) o geologic history, 137 (illust.) Mosasaurus (mose-a-SAWR-us), Mesosaurs, 105 114; in synoptic table, 141 Oceans, distribution of in past, Mesosaurus (mes-o-SAWR-us), 104 Mosclwps (Mos-kops. From theories of, 128, 129 (illust.), 105; in synoptic table, Greek, moschios—"a young Odon, from Greek, odous, odon, 139 calf" + ops—"head or face"; so odontos—'tooih" Mesosuchia (mes-o-sooK-e-ya. named because the skull of Oldest fossils, 38 (diagr.) From Greek, mesos—"middle" this reptile resembles super- Ophiacodon (o-fee-A-ko-don. + souchos—"crocodile." These ficially die skull of an ox.), 54 From Greek, ophiacos—"per- are the intermediate crocodiles, (illust.), 57, 58; in synoptic taining to a serpent" + odous, between the most primitive table, 139 odon—"tooth"; with teeth like forms and the modern types.), Mounting fossils for exhibition, those of a serpent.), 55; in

119, 120; in synoptic table, 141 34 (illusts.) synoptic table, 139

151 '

Ophiacodonts, description of, 56 Overspecialization in evolution, phos-"crest"].), 78 (illust.); Ophidia, in synoptic table, 141 115 breathing mechanism of, 86

Origin of the earth, 38 (illust.) Ovoviviparous reproduction, as in (illust.), 87; head of, 76 Origin of Species, The, 18, 126 aquatic reptiles, 108 (illust.); in synoptic table, 141; Ornithischia (orn-ith-iss-kee-ya. Owen, Richard, 16 (portrait), 17, time and distribution of, 95, 96 From Greek, ornis, ornithos— 23, 64 Pariasaurus (par-EYE-a-sawr-us. "bird" + ischion—"hip"; so From Greek, pareia—"check" named because the hip or + sauros—"lizard"; so named

pelvis is similar to that in the because of the heavy bone on Pachycephalosaurus (pak-e-sEF-a- birds.), 52 (illust.), 73-83; de- the side of the skull in this lo-sawr-us. Greek, pachys scription of, 65; in synoptic From ancient reptile.), description of, —"thickness" kephalon— table, 140, 141; jaws of, 89, + 50, 51; in synoptic table, 138; "head" sauros— "lizard."), 90; means of defense, 90-91; -f- Scutosaurus, 51 (illust.) brain size of, 90 (illust.); de- California Institute pelvis of, 65 (illust.); span in Pasadena, of scription of, 77; in synoptic geologic history, 137 (illust.); Technology, 24 table, 141 Passaic, teeth of, 88 New Jersey, 51 Packing fossils for shipment, 32 Ornitholestes (orn-i-tho-LES-teez. Peabody Museum of Yale Uni- Palaearctis, 128 versity, 24 From Greek, ornis, ornithos— 22, Palaeo or paleo (pale-c-o), from Pelvis of ornithischian dinosaurs, "bird" + lestes— "robber"; so Greek, palaios—"ancient" 65 (illust.); of saurischian dino- named because this small dino- Palaeoscincus (pale-e-o-sxiNK-us. saurs, 64 (illust.); of a theco- saur was pictured in the im- From Greek, palaios—"ancient" dont, 61 (illustj agination as catching the prim- skinkos—"lizard," in refer- Pelycosauria (pel-i-ko-SAWH-e-ya, itive bird, Archaeopteryx.), 67 + ence to tooth structure, re- From Greek, pelyx, pelycos— (illust.), 90, 94; bone structure sembling that of a modern "a basin" sauros—"lizard"; of, 68; habits of, 85; in syn- + skink.), 78 (illust.), 79, 95, 96; so named in reference to the optic table, 140; means of de- in synoptic table, 141 form of the pelvis.), evolution fense, 90; time and distribu- Paleogeography, 127-129 of, 53-56; family relationships tion of, 94, 95 Paleontology (pale-e-on-TOL-o- of, 52 (illust.); in synoptic Ornithopoda (orn-i-THO-pod-a. gee. From Greek, palaios— table, 139; distribution and From Greek, ornis, ornithos— "ancient" -\- on, onta—"beings" span in geologic history, 131 "bird" + pons, podos—"foot"; -f- logia—"to speak"; hence, to (table), 132, 137 (illust.) hence with birdlike feet.), 73- speak of ancient beings, or to Pennsylvanian period, 39 77; in synoptic table, 140, 141 study ancient life.), books on, Permian period, 39; in South Ornithopods (oHN-i-tho-pods), 66 142, 143; cultural importance Africa, 22, 23; in Texas, 22 (illust.), 73-77; time and dis- of, 126; development of as a Philadelphia, Academy of Nat- tribution of, 131 (table) science, 15; economic impor- ural Sciences, 18, 20 Ornithosuchus (orn-i-tho-sooK-us. tance of, 125; function of, 15; Phohosuchus (fobe-o-sooK-us. From Greek, ornis, ornithos— possibility of new discoveries From Greek, phobos—"fear" + "bird" souchos—"crocodile." + in, 130 souchos—"crocodile"; a good A "birdlike reptile," because of Paleozoic era, 25, 41 name, for of all the crocodiles the light build and bipedal Parallelism of phytosaurs and this was the most fearsome.), pose.), 61; in synoptic table, crocodilians, 62, 63 description of, 120; in synoptic 140 Parapsida (pear-APS-i-da. From table, 141 Osborn, Henry Fairfield, 19 (por- Greek, para—"beside" + ap- Phytosauria (fite-o-SAWR-e-ya. trait), 21, 23 sides— "arches," in reference to From Greek, phyton—"plant" Osteichthyes (os-tee-ik-THi-ees. the temporal opening behind -4- sauros—"lizard"; so nameti From Greek, osteon— "bone" + the eye.), 104-110; definition because it was first supposed ichthys—"fish." The bony fish.) of, 48, 49; in synoptic table, that these thecodont reptiles Osteolepis (os-te-o-LEEP-is. From 139; parapsid skull, 49 (illust.); were plant eaters. It is now Greek, osteon—"bone" + lepis— span of Parapsida in geologic evident thai they were strictly "scale"; so named because of history, 137 (illust.) carnivorous.), ancestors of the the heavy scales.), 41 (illust.) ParasauTolophus (par-a-sawr-AH- crocodiles, 118, 119; descrip- "Ostrich dinosaur," Strutliionii- lof-us. From Greek, para—"be- tion of, 62, 63 (illust.); in syn- mus, 70, 95 side" + Saurolophus, meaning optic tabic, 140; parallelism Ottawa, National Museum of similar to the dinosaur Saurolo- with crocodilians, 62, 63; time Canada, 22, 24 phus [sauros—"lizard" + lo- and distribution of, 131 (table)

152 Pineal opening, 50, 51, 58, 61 Plesiosaurus, 17; in synoptic table, ships.), in synoptic table, 140 Pioneer students of the dinosaurs, 140 Psittacosaurus (sit-a-ko-SAWR-us. 15 Pleurodira (plur-o-DiRE-a. From From Greek, psittakos— "par- Pittsburgh, Carnegie Museum, Greek, pleura—"the side" + rot" + sauros—"lizard"; so 22, 24 deira—"neck." Those turtles in named because of the shape Pituitary body of the dinosaurs, which the neck is bent to the of the skull.), description of, 93 (Must), 116 side when the head is re- 80; head of, 82 (illust); in Placochelys (plak-o-KEEL-is. From tracted into the shell.), 123, synoptic table, 141 Greek, plax, plakos—"a. plate" 124 (illust.); in synoptic table, Pteranodon (ter-AN-o-don. From + chelys—"tortoise"; so named 139 Greek, pteron—"wing" + ano- because of the tortoise-like Pliosaurs, 111 dous, anodontos — "without armor over the body. This Poisonous snakes, character of teeth." A toothless flying rep- name does not indicate any skull of, 122 tile.), 98 (illust.), 99; in synop- zoological relationships with Porpoises, comparison of with tic table, 141 the tortoises.), 112; in synoptic aquatic reptiles and fishes, 108- Pterodactyloidea (ter-o-dakt-il- table, 140 110 oro-e-ya. From Greek, pteron— Placodermi (plak-o-DERM-i. From Preparation of fossils, 33 (illust.), "wing" + daktylos—"finger"; Greek, plax, plakos—"a plate" 34 so named because the wing + derma—"skin." A group of Price, Garrett, cartoon by, 12 was supported by the fourth primitive fishes with heavily Primitive reptiles, 47 finger.), in synoptic table, 141 armored bodies.) Princeton University, 21 Pterosauria (ter-o-SAWR-e-ya. From Placodontia, in synoptic table, Procolophon (pro-KOL-o-fon. From Greek, pteron—"wing" -\- sau- 140 Greek, pro—"before, in front ros—"lizard." The flying rep- Placodonts (pLAK-o-dahnts), 110- of" + kolophon—'a. summit or tiles.), description of, 97-99; 112 pinnacle."), 51; in synoptic- in synoptic table, 141; span in Placodus (pLAK-o-dus. From table, 138 geologic history, 137 (illust.) Greek, plax, plakos—"a. plate" Procolophonids, 51 Pterosaurs, 17, 97-99, 100 (il- + odous—"tooth"; so named Protoceratops (prot-o-SER-at-ops. lust.); family relationships of, because of the broad teeth.), From Greek, protos—"first" + 52 (illust.) 109 (illust); description of, keratos—"horn" + ops—"face." Publication of studies on fossils, 111, 112; in synoptic table, 140 The first of the horned dino- 34, 35 Plant-eating dinosaurs, adapta- saurs.), 80, 134; description of, Pythons, 122

tions in feeding of, 88, 89; kinds 79 (illust.), 80; eggs of, 80, 81 and activities of, 94-96 (illust.); head of, 82 (illust); Plastron, of turtle, 124 in synoptic table, 141 Plateosaurus (plat-e-o-SAWR-us. Protorosauria, in synoptic table, Quadrupedalism, secondary re- From Greek, plata—"flat" + 139 turn to in dinosaurs, 67 (diagr.) sauros—"lizard."), 72; in syn- Protorosaurus (prot-or-o-SAWH-us. optic table, 140 From Greek, proteros— "earlier" R Plesiosauria (plees-i-o-SAWR-e-ya. + sauros—"lizard."), 110; in From Greek, plesios—"near" + synoptic table, 139; span in "Racial senescence" in dinosaurs, sauros—"lizard"; so named be- geologic history, 137 (illust.) 115 cause the genus Plesiosaurus Protosaurs (pROT-o-sawrs), 110 Radioactive materials in deter- was originally supposed to be Protosuchia, in synoptic table, 141 mining age of rocks, 36 closely related to the lizards.), Protosuchus (prot-o-sooK-us. From Removal of fossils, 31 (illust.), 32 in synoptic table, 140 Greek, protos—"first" + sou- Reproduction in amphibians and Plesiosaurs, 17, 104; ancestry of, chos—"crocodile."), 119 (il- reptiles, 47; in aquatic rep- 110; compared with ichthyo- lust.); ancestry of, 118; and tiles, 108 saurs and marine turtles, 111; phytosaurs, 118; description of, Reptiles, Age of, 36, 37, 39 description of, 110-112; distri- 118; in synoptic table, 141; Reptiles, classification of, 48, 138- bution of, 131 (table), 132; time and distribution of, 118, 141; definition of, 47; evolu- evolution of, 110-112; family 119 tion of, 47-52 (diagr.), 118-124;

relationships of, 52 (illust.); Pseudosuchia (sood-o-sooK-e-ya. family tree of, 52 (diagr.); first in synoptic table, 140; method From Greek, pseudos—"false" appearance of, 38 (diagr.), 47; of swimming, 111; span in geo- + souchos— "crocodile." These kinds of, 118-124; prehistoric logic history, 131 (table), 137 reptiles look like crocodiles but distribution of, 127-132; repro- (illust.) are of independent relation- duction in, 47; skulls, five bas-

153 ic types of, 48, 49 (illust); Saltoposuclius (sal-to-po-sooK-us. Scutosaurus (scute-o-SAWR-us. span in geologic history, 137 Derivation of term not defi- From Greek, skutos—"a shield

(illust.). See also Aquatic rep- nitely known.), 61, 62 (illust.); or buckler" -f sauros—"lizard"; tiles, Mammal-like reptiles, in synoptic table, 140 so named because of the very Marine reptiles, and Flying Saurischia (sawr-iss-kee-ya. From heavy dermal scutes that pro- reptiles Greek, sauros—"lizard" + is- tected this Permian reptile.), Reptilia (rep-TiLL-e-ya. From chion—"hip." The dinosaurs 51 (illust.); in synoptic table, Latin, reptilis—"a creeping ani- having a pelvis of reptilian 138 mal."), 136; in synoptic table, form.), 65; in synoptic table, Sea-lizards, mosasaurs, 112-114 138-141 140 Sea Serpents, 104 Restoration of fossils, 35 Saurischian dinosaurs, 64 (illust.); Senescence, racial, as in evolu- Rhachitomi (rak-iT-o-me. From description of, 65; development tion, 115 Greek, rachis— "the spine" + of, 68-73; eating mechanism Serpents, evolution of, 104-114 tomia—"cut"; in reference to of, 88 (illust.), 89; family re- Seymouria (see - moor - e - ya. the structure of the vertebrae.), lationships of, 52 (illust.); in Named from the town of Sey-

43; in synoptic table, 138 synoptic table, 140; span in mour, Texas ), 48, 50 (illusts.), Rhamphorhynchoidea, in synop- geologic history, 137 (illust.) 105; in synoptic table, 138 tic table, 141 Sauropoda (sawr-o-pod-a. From Seymouriamorpha (From English Rhamphorhyjichus (ram-fo-RiNK- Greek, sauros—"lizard" + pous, and Greek, Seymouria + mor- us. From Greek, ramphos— podus—"foot."), 70-73; in syn- pha—"form." Reptiles related "prow" + rynchos—"beak."), optic table, 140 to Seymouria.), 50; in synop- 98 (illust.); in synoptic table, Sauropods (sAWB-o-pods), aquatic tic table, 138 141 specializations in, 87; devel- Shakespeare, 135 Rhynchocephalia (rink-o-sef-AY- opment of, 67; eating spe- Shell construction in turtles, 124 le-ya. From Greek, rynchos— cializations in, 88; family rela- Side-neck turtles, 123 "snout" + kephalon—"head."). tionships of, 66 (illust.); jaws Size of dinosaurs, 84, 85 Champsosaurus, 121 (illust.); of, 89; pituitary development Skin, fossilized, 26 (illust.) evolution of, 121, 122; family in, 93; means of defense, 92; Skinks, 122 relationships of, 52 (illust.), size of, 84; teeth of, 88; time Skulls, different types of in rep- 121; in synoptic table, 140; and distribution of, 131 (table) tiles, 48, 49 (illust.) Sphenodon, 121 (illust.); time Sauropterygia (sawr-op-ter-ij-e- Snakes, 122; family relationships and distribution of, 131 (table), ya. From Greek, sauros— "liz- of, 52 (illust.); in synoptic 137 (illust.) ard" + pteryx—"fin."), 109 (il- table, 141; span in geologic Romer, Alfred S., 7, 23, 49 lust.), 110-112; in synoptic historv, 131 (table), 132, 137 Royal College of Surgeons (Lon- table, 139, 140; span in geo- (illust) don), 17 logic history, 137 (illust.) Soft parts, fossilization of, 30 Royal Ontario Museum, Toronto, Sauros (Greek, meaning "lizard.") Solenhofen limestones of Bavaria, 22, 24 As has been seen, this is a 102 Rutiodon (Roo-ti-o-don. From hard-worked word, used in South Africa, Permian of, 22, 23; Greek, rhytis—"plant" + odon making combinations to name Triassic of, 23 —"tooth"; so named because various types of reptiles, living Specializations in dinosaurs, 84- these reptiles were first sup- and extinct. Although in the 93 posed to feed upon plants.), in Greek sense sauros means liz- Species, as a division in the

synoptic table, 140 ard, it might be better translated Linnaean system of nomencla- as reptile. Most of the reptiles ture, 133-136 that have a sauros in their Sphenacodon (sfen-AK-o-don. name are not lizards, nor are From Greek, sphen—'& wedge" Salamanders, family relationships they related to the lizards; con- + oiak—"rudder" + odon— of, 46; in synoptic table, 138; sequently one must not make "tooth."), 55, 56 time and distribution of, 131 the mistake of thinking that Sphenodon (sFEN-o-don. From (table), 137 (illust.) the term sauros carries any in- Greek, sj)hen—"d wedge" + Salientia (sal-e-ENT-e-ya. From dication or connotation of zoo- odous, odon— "tooth."), 50, 121

Latin, salient,, -entis— "leap." logical relationships (illust.); in synoptic table, 140 The leaping amphibians, frogs Scientific names, formation of, Squamata (skwa-MAH-ta. From and toads.), in synoptic table, 134, 135 Latin, squamatus—"scaly." The 138; span in geologic history, Sclerotic plates, 107 scaly reptiles, namelv the liz-

137 (illust.) Scott, William Benyman, 21 ards and snakes.), 122, 136; in

154 L synoptic table, 141; span in synoptic table, 139; span in Therapsida (ther-APS-i-da. From geologic history, 137 (illust.) geologic history, 137 (illust.) Greek, ther—"n beast" + ap- be- Stahlekeria (stal-le-KER-e-ya. Synapsids, appearance of, 53; sides— "opening"'; so named Named in honor of Dr. Rudolf disappearance of, 53; evolu- cause the temporal region of Stahleker of Tubingen Univer- tion of, 53-59 the skull is very much like the

sity, Germany.), 57; in synop- Synoptic table of the Amphibia same part of the mammal tic table, 139 and Reptilia, including the skull.), 53, 54 (illust.); in syn- Stegosauria (steg-o-SAWR-e-ya), genera mentioned in this book, optic table, 139; span in geo- 77, 78; in synoptic table, 141 138-141 logic history, 137 (illust.) Stegosaurs, family relationships System under which all animals Therapsids, distribution of, 132; of, 66 (illust.); means of de- and plants are classified, 136 evolution of, 56-59; family re- fense, 91; time and distribution (diagr.) lationships of, 52 (illust.) of, 131 (table) Systema Naturae, Linnaeus, 133, Theriodontia (dier-e-o-DONT-e-ya. Srego«2urus(steg-o-SAWR-us. From 134 From Greek, therion—"a wild odous, odontos— Greek, stegein—"cover" + beast" -f- sauros—"lizard"; in reference "teeth"; so named because the to the armor covering the teeth resemble in form those of

of, 77 (il- the mammals.), in synoptic back.), description Tail of ichthyosaur, 107, 108; of table, 139 lust.), 78; in synoptic table, marine crocodiles, 114 nervous system of, Theriodonts, 58, 59 141; 78, Taylor, Bert Leston, poem by, 78 92 (illust.), 93; time and dis- Theropod dinosaurs, 87-89 Teeth and jaws of dinosaurs, 88 tribution of, 94, 95 Theropoda (ther-o-pod-a. From Teleosaurus (teel-e-o-SAWR-us. Stereospondyli (ster-e-o-spoN-dil- Greek, ther—"a. beast" [or a From Greek, teleos—"com- ee. From Greek, stereos— mammal] + pous, podos— plete" -f- sauros—"lizard."), "solid" + spondijlos—'verte- "foot."), 68-70; in synoptic 120; in synoptic table, 141 bra."), 43; in synoptic table, table, 140 Territorial Surveys (of the United 138 Theropods (THER-o-pods), 68-70; States), 20, 25 Struthiomimus (strooth-ee-o- family relationships of, 66 (il- Testudinata (tes-TOOD-e-na-ta. mime-us. From Greek, strou- lust.); Ornitholestes, 67 (il- From Latin, testudo, testudinis thion—"ostrich" 4- mimos—"an lust.); means of defense, 90; -"a tortoise."), 123 imitator"; so named because of specializations in for eating, Tethys, 128 its ostrich-like appearance.), de- 87, 88; time and distribution Tetrapoda (tet-ra-POAD-a. From scription of, 70, 71 (illust.), of, 131 (table) Greek, tetrapodes— "four-foot- 78 (illust.); eating mechanism Thomson, Albert, 21 ed." The land vertebrates.), 61 of, 88, 89; in synoptic table, Titanosuchus (tye-tan-o-sooK-us. Texas, Permian of, 22 140; means of defense, 90; From Greek, titan—"titan" + Thalattosuchia, in synoptic table, time and distribution of, 95 souchos—"crocodile"; so named 141 Students of dinosaurs, pioneer, 15 because of its large size. This Thecodont pelvis, 61 (illust.); Study of fossils, 34 reptile is not a crocodile but skeleton, Styracosaurus (sty-rak-o-SAWR-us. 61, 62 a therapsid.), 57; in synoptic From Greek, styrax—"spike" + Thecodont reptiles, 132 table, 139 sauros—"lizard"; so named in Thecodontia (theek-o-DONT-e-ya. Toads, in synoptic table, 138; Greek, theka—"case" -)- • reference to the spikes around From time and distribution of, 131

the frill of this horned dino- odous, odontos— "tooth"; so (table), 137 (illust.) saur.), 95, 96, 134; description named because the teeth are Toronto, Royal Ontario Museum, of, 83; head of, 82 (illust.); in set in sockets in the jaws.), 60; 22, 24 synoptic table, 141; time and family relationships of, 66 (il- Trachodon (TRAK-o-don. From distribution of, 95, 96 lust.); in synoptic table, 140; Greek, trachys—"rough" + Synapsid reptiles, evolution of, span in geologic history, 137 odous, odon—"tooth"; so 54 (diagr.) (illust.) named because the teeth form Synapsid skull, 49 (diagr.) Thecodonts, description of, 60- a rough sort of pavement.), 24, Synapsida (sine-APS-i-da. From 62; distribution of, 132; ex- 74 (illust.), 78 (illust.); de- Greek, syn—"beside, together" amples of primitive genera, 61; scription of, 76; in synoptic + apsides—"arches." Reptiles hips of, 61 (illust.); family re- table, 141; jaw mechanism of, having a lower temporal open- lationships of, 52 (illust.) 89 (illust.); time and distribu- ing behind the eye.), definition The Dinosaur (poem), 78 tion of, 95, 96 and classification of, 48; in Therapsid reptiles, 56-59 Trachodont dinosaurs, evolution

155 of, 75, 76; calcification of ten- Two-footed development of Varanus (var-AN-us. From Arabic, dons in tail, 87 dinosaurs, 65-68, 67 (illust.) waran; French, varan, etc. A Trachodonts, 75, 76; breathing Tylosaurus (tile-o-SAWR-us. From monitor lizard.), 122; in synop- mechanism of. 87; crests on Greek, tylos—'a. knot" + sauros tic table, 141 skull, 87; means of defense, 90, -"lizard."), 112 (illust.), 113; Vertebrae of Brontosaurus, adap- 91 in synoptic table, 141 tations of, 85 Transition from Cretaceous to Tyrannosaurus (tye-ran-o-SAWR- Vertebrate, from Latin, vertebra- Eocene, 117 us. From Greek, tyrannos— tus— "jointed" Transition in vertebrates from "tyrant" -+- sauros—"lizard."), Vertebrate paleontology, histori-

water to land life, 42 69 (illust.), 92; adaptation to cal development of, 15-23

Tree-climbing dinosaurs, 87 large size, 84, 85; bone struc- Vertebrates, first appearance of, Triassic, of South Africa, 23 ture of, 84, 85; description of, 41; transition from water to Triassochelys (try-as-o-KEEL-is. 70; eating mechanism of, 88; land life, 42

From Greek, trias—"three," also habits of, 85; in synoptic table, Vertebrates, flying, evolution of, the Triassic period + chelys 140; specializations in, 84, 85; 97-103 —"tortoise." A primitive turtle time and distribution of, 95, 96 Vertical-neck turtles, 123 of Triassic age.), 124; in synop- Tyrannosaurus rex, derivation of tic table, 139 name, 135 w Triceratops (try-SER-at-ops. From Greek, treis—"three" + keras, u Walker Museum of the Univer- keratos—"horn" + ops—"face." sity of Chicago, 23, 24 Three horns on the skull.), 92, United States National Museum, Wealden (Lower Cretaceous), 15 134; description of, 81 (illust.), 22, 24 Weyer, Edward M., 7 83; head of, 82 (illust.); in University of California, Museum Where dinosaurs and their rela- synoptic table, 141; means of of Paleontology, 23, 24 tives are found, 127 defense, 92 University of Chicago, Walker Why study fossils?, 125 Trivial name, in scientific no- Museum of, 23, 24 Williston, Samuel Wendell, 23 menclature, 133-136 University of Kansas, 23 Wing, construction of in bat, Troodon (TRO-o-dahn. From University of Kansas, Dyche Mu- bird, and flying reptile, 99, Greek, two—"to wound" + seum, 24 100 odous, odon— "tooth"; so named University of Michigan, Museum Wormian, Jacob, 21 because Leidy, who first de- of, 23 scribed this dinosaur, was im- University of Pennsylvania, 20 pressed by the sharp, cutting Upland dinosaurs, 85-87

nature of the teeth.), 91 (il- Urodela (your-o-DEEL-a. From Yale University, 20; Peabody lust.); in synoptic table, 141 Greek, oura—"tail" + delos— Museum of, 22, 24 Troodont dinosaurs, 76, 77; brain "manifest." The amphibians Youngina (young-EYE-na. Named

and pituitary body of, 93 (il- with tails; the salamanders.), in honor of Mr. John Young of

lust.); means of defense, 91 family relationships of, 46 (il- the Hunterian Museum, Glas-

(illust.); skull of, 91 lust.); in synoptic table, 138; gow University.), description Tuatara, 50, 121 (illust.) span in geologic history, 137 of, 60; in synoptic table, 140 Turtles, 123 (illust.), 124; distri- (illust.) Youngoides (young-oY-deez), 60 bution of, 131 (table), 132; (illust.); in synoptic table, 140

family relationships of, 52 (il- Yunnan Province, China, 23

lust.); in synoptic table, 139; marine, comparison with plesi- Varanids, 113 osaurs, 111; span in geologic Varanosaurus, 53, 54 (illust.); in history, 137 (illust.) synoptic table, 139 Zittel, Karl von, 21

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AMNH LIBRARY

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