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WATER REPTILES OF THEPAST AND PRESENT
WATER REPTILES OF THEPAST AND PRESENT
BY Samuel Wendell Williston Professor of Paleontology in the University of Chicago THE UNIVERSITY OF CHICAGO PRESS CHICAGO, ILLINOIS Copyright 1914 by The University of Chicago All Rights Reserved Published October 1914 Composed and Printed By The University of Chicago Press Chicago, Illinois, U.S.A....
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PREFACE
PREFACE
It was just forty years ago that the writer of these lines, then an assistant of his beloved teacher, the late Professor B. F. Mudge, dug from the chalk rocks of the Great Plains his first specimens of water reptiles, mosasaurs and plesiosaurs. To the youthful collector, whose first glimpse of ancient vertebrate life had been the result of accident, these specimens opened up a new world and diverted the course of his life. They were rudely collected, after the way of those times, for modern meth
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CHAPTER I INTRODUCTION
CHAPTER I INTRODUCTION
In most persons the word reptile incites only feelings of disgust and abhorrence; to many it means a serpent, a cold, gliding, treacherous, and venomous creature shunning sunlight and always ready to poison. Our repugnance to serpents is so much a part of our instincts, or at least of our early education, that we are prone to impute to all crawling creatures those evil propensities which in reality only a very few possess. Were there no venomous serpents—and there are but two other venomous rept
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CHAPTER II CLASSIFICATION OF REPTILES
CHAPTER II CLASSIFICATION OF REPTILES
There is very much doubt, very much uncertainty, among paleontologists about the classification of reptiles. No two writers agree on the number of orders, or the rank of many forms. Some recognize twenty or more orders, others but eight or nine. And this doubt and uncertainty are due chiefly to the many discoveries of early forms that have been made during the past twenty years. The many strange and unclassifiable types which have come to light in North America, South Africa, and Europe have thr
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SKULL AND TEETH
SKULL AND TEETH
The skull of reptiles is much more primitive or generalized in structure than is that of mammals, to such an extent, indeed, that there is yet much doubt as to the precise homologies of some of the bones composing it; and, inasmuch as the names were originally given, for the most part, to the bones of the human skull, there is still some confusion among students as to the proper names in all cases, a confusion that doubtless will not be wholly dissipated until we know much more about the early o
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VERTEBRAE AND RIBS
VERTEBRAE AND RIBS
The spinal column or backbone of reptiles, as in all air-breathing vertebrates, is made up of a variable number of separate segments called vertebrae, permitting flexibility. Each vertebra is composed of a body, or centrum, and an arch on the dorsal side for the protection of the spinal cord. Various projections from the vertebra, called processes, serve for the attachment of ligaments or muscles, for articular union with adjacent vertebrae, or for the support of ribs, and these processes have c
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PECTORAL OR SHOULDER GIRDLE
PECTORAL OR SHOULDER GIRDLE
Those bones which form the framework for the support of the anterior extremity in vertebrate animals are known collectively as the pectoral girdle. In our own skeleton there are but two on each side, or four in all, the scapula or shoulder-blade, and the clavicle or collar-bone. A third bone, however, is represented in all mammals by a mere vestige which early unites with the scapula and is called the coracoid process. In the lowest forms of mammals, the Monotremata, of which the Ornithorhynchus
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ANTERIOR EXTREMITY
ANTERIOR EXTREMITY
The upper arm bone, or humerus, like most other bones of the extremities, has been greatly modified by the habits of the different reptiles. In running and climbing reptiles it is always slender, while in burrowing reptiles it is short and stout and much expanded at the extremities, like the humerus of the mole among mammals. And we shall also see how greatly modified it was among the swimming reptiles. The humerus of flying reptiles has an enormous process on the side, corresponding to the atta
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PELVIC OR HIP GIRDLE
PELVIC OR HIP GIRDLE
The pelvic girdle or pelvis in reptiles and higher animals consists of three bones on each side, often closely fused in adult reptiles and together known as the innominate bone. The upper or dorsal one of these three bones—that to which the sacrum is attached—is the ilium; the one on the lower or ventral side in front is the pubis; and that on the ventral side behind is the ischium. On the outer side, where these three bones meet, is a cup-like depression, sometimes a hole, called the acetabulum
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POSTERIOR EXTREMITY
POSTERIOR EXTREMITY
The thigh bone or femur in reptiles, like the humerus, is variable in size and shape. Only in those reptiles that walked erect is the articulation of the head set off from the shaft of the bone by a distinct neck. In others the articulation is at the extreme top of the bone, since the thigh bones are habitually turned more or less directly outward from the acetabulum and the long axis of the body. The more or less pronounced rugosities at the upper end of the femur, for the attachment of muscles
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EXTINCT REPTILES OF NORTH AMERICA
EXTINCT REPTILES OF NORTH AMERICA
The oldest known fossil reptile of North America, or indeed of the world, is represented by a single specimen, lacking the skull, from black shales of Middle Pennsylvanian age overlying a coal seam at Linton, Ohio. The specimen was originally described as an amphibian, but was later recognized by Professor Cope as a true reptile. It was more fully described by the writer under the name Eosauravus Copei , who agreed with Cope as to its reptilian nature. Until the skull is discovered, however, the
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CHAPTER V ADAPTATION OF LAND REPTILES TO LIFE IN THE WATER
CHAPTER V ADAPTATION OF LAND REPTILES TO LIFE IN THE WATER
In the never-ceasing struggle for existence all forms of life upon the earth, whether consciously or unconsciously, are continuously striving for improvement; striving to flee from adverse environments, or to adapt themselves better to those which must be endured; to escape their enemies, or to find means whereby they may withstand them; to find more or better food, or to prevent others from despoiling them of what they have. There is always more or less of unrest, more or less of discontent, if
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PLESIOSAURIA
PLESIOSAURIA
It was Dean Buckland who facetiously likened the plesiosaurs to a snake threaded through the shell of a turtle, and the simile was not an inapt one in his day. The vernacular designation of them—long-necked lizards—conveys the same impression of their chief peculiarity, but the name is less applicable than it once was, since recent discoveries have brought to light forms with a relatively short neck. Though the plesiosaurs are nearly perfectly adapted to an aquatic life, the adaptation was, in m
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NOTHOSAURIA
NOTHOSAURIA
A few years after the discovery of the plesiosaurs by Conybeare, the remains of animals of allied kinds were found in the Triassic rocks of Bavaria. At first they were supposed to be those of true plesiosaurs, and even the astute Cuvier was not very clear about them. Cuvier was the first to call attention to them, expressing the opinion that some of the fossils were of previously unknown animals allied to the crocodiles, lizards, and plesiosaurs. It was von Meyer, however, who first introduced a
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CHAPTER VII ANOMODONTIA
CHAPTER VII ANOMODONTIA
LYSTROSAURUS Over a large area of South Africa, chiefly along the Orange River and its tributaries, there is an extensive series of deposits many hundreds of feet in thickness, usually called the Karoo beds, which, for more than fifty years, have been widely famous among scientific men for the many and remarkable vertebrate fossils which they have yielded. These deposits seem to represent the whole of the vast interval of time from the Carboniferous to the Jurassic, that is, the whole of the Per
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CHAPTER VIII ICHTHYOSAURIA
CHAPTER VIII ICHTHYOSAURIA
Early in the eighteenth century a curious work in the Latin language was published by a famous physician and naturalist—a professor in the University of Altorf by the name of Scheuchzer—entitled Querulae Piscium , or “Complaints of the Fishes.” The work was illustrated by many expensively engraved figures of various fossil remains, including one of some vertebrae which the author referred to as “the accursed race destroyed by the flood”! The history of the finding of these famous bones is record
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CHAPTER IX PROGANOSAURIA
CHAPTER IX PROGANOSAURIA
MESOSAURUS There is some doubt whether those little creatures of Paleozoic times, to which some years ago the late Professor Baur gave the ordinal name Proganosauria, are really entitled to so much distinction among reptiles. The question of their rank has been much disputed for the past twenty years without any positive conclusion. Nor were they wholly aquatic in habit, though they did possess many aquatic adaptations. That they were skilful and fleet swimmers, and capable of rapid evolutions i
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PROTOROSAURUS
PROTOROSAURUS
The genus Protorosaurus is of peculiar interest, as one of the first, if not the first, known fossil reptiles, described by Spener as long ago as 1710 as a crocodile, from fragmentary remains found in 1706 in the Permian deposits of Thuringia. Numerous other skeletons or parts of skeletons attracted the attention of naturalists of the eighteenth century, but were very imperfectly described. No name was given to the animal represented by the various specimens until 1840, when Herman von Meyer res
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PLEUROSAURUS
PLEUROSAURUS
We may for the present be justified in maintaining the order Protorosauria for those reptiles having a single, typically upper temporal opening on each side, with a fixed quadrate, not including the ichthyosaurs. It is not improbable, however, that when more is known of the ancestors of the lizards, the whole group will find its most natural place among the Squamata. This definition will include a peculiar aquatic reptile that has been known for many years, but which has been wrongly classed in
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LIZARDS
LIZARDS
Popularly a lizard is any four-legged reptile covered with scales, but such a definition is not strictly correct, since some lizards are legless and some other four-legged reptiles are covered with horny scales, notably the tuatera or Sphenodon of New Zealand, a reptile long classed with lizards, but now known to belong to quite a different order. Bearing in mind those characters given as characters of the order, it will be necessary to mention only those distinguishing the lizards from the snak
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MOSASAURS
MOSASAURS
At St. Pietersberg, a small mountain in the vicinity of Maestricht, Holland, there are immense subterranean stone quarries, which have been worked for more than a thousand years. The stone quarried from them is a sandy limestone of Upper Cretaceous age containing many well-preserved remains of extinct animals that have long been sought by collectors of fossils. In 1776 Major Drouin—an officer of a near-by garrison, one of much military importance in those days—secured from one of these quarries
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SNAKES
SNAKES
The chief differences between snakes and lizards have already been given and need not be repeated, save very briefly. Snakes are always functionally legless, though some have vestiges of the hind pair; the brain-case is wholly bony; the upper temporal bar is wanting; the lower jaws are united in front by ligaments only, like those of the mosasaurs; the vertebrae are greatly increased in number, and always have the additional zygosphenal articulations like those of Clidastes and Mosasaurus and so
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CHAPTER XII THALATTOSAURIA
CHAPTER XII THALATTOSAURIA
Millions of years before the first appearance of the mosasaurs in geological history, another group of reptiles showing many curious resemblances to them attempted a rather precarious existence in the water. Its members survived long enough to acquire many structural adaptations to a water life, long enough to become diversely modified, but not long enough, apparently, to wander far from their birthplace, not long enough to attain that security from their enemies and more ambitious competitors,
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RHYNCHOCEPHALIA
RHYNCHOCEPHALIA
In some of the small islands near the northeast coast of New Zealand certain small and peculiar, lizard-like reptiles, known as tuateras, have long been known. For many years they were supposed, even by scientific men, to be real lizards, so much do they resemble in external appearances and in habits the lizards of other parts of the earth. It was early observed, however, that they presented certain remarkable internal differences from the real lizards or Lacertilia, though it was not till about
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CHORISTODERA
CHORISTODERA
Among the many reptiles of the past which have sought a more congenial or a safer home in the water few have had a more interesting history, or a briefer one, than those to which the late Professor Cope gave the name Choristodera in 1876. Many students of repute consider the group an order, others a suborder of the Rhynchocephalia. The group, whether order or suborder, are interesting because of their long and devious migrations from western North America to Europe, or vice versa, through rivers
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PARASUCHIA
PARASUCHIA
The first known specimen of the order of reptiles now generally known as the Parasuchia was found in Würtemberg, Germany, in 1826 and very briefly and inadequately described [4] two years later by Professor George Jaeger. The specimen was a sorry one, and was sadly misinterpreted by Jaeger. It consisted chiefly of casts of the alveoli or sockets of a number of teeth, more or less connected by corroded or decomposed portions of the jaws. He recognized the casts as teeth of a peculiar reptile, but
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PHYTOSAURIA
PHYTOSAURIA
The Phytosauria, so far as known, were all reptiles of considerable size, greatly resembling the crocodiles, and especially the gavials in form and habit, but differing very greatly in having the external nostrils situated far back near the eyes; in having no false palate so characteristic of the Crocodilia; in having a more primitive shoulder-girdle, consisting of a short coracoid, interclavicle, and clavicles; and in having the ordinary type of pelvis, that is, with the pubis entering into the
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MODERN CROCODILES, EUSUCHIA
MODERN CROCODILES, EUSUCHIA
The crocodiles of the present—and we use the word in the technical sense of Crocodilia—because of their general resemblance to the lizards, or true “saurians,” were classed with them by the older naturalists, whence comes the popular name alligator, a corruption of the Spanish el lagarto , or “the lizard,” given to some of the South American forms by early explorers. But this resemblance is a superficial one only, as was early recognized by comparative anatomists. The crocodiles, indeed, are onl
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ANCIENT CROCODILES, MESOSUCHIA
ANCIENT CROCODILES, MESOSUCHIA
The name Mesosuchia, meaning “middle crocodiles,” by which the ancient members of the Crocodilia have generally been known, was given by Huxley in the belief that they were intermediate between the “true” or modern crocodiles and an ancient group which he united with the order under the name “Parasuchia.” A fuller and better knowledge of the members of this last group has proved very conclusively that they are really less allied to the crocodiles than are some other orders of reptiles, the dinos
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MARINE CROCODILES, THALATTOSUCHIA
MARINE CROCODILES, THALATTOSUCHIA
While the ancient crocodiles of which we have spoken resembled the modern ones so closely in form of body and probably in habits, there were certain others of the old Jurassic seas which departed so widely both in structure and in habits, from their associates that they are by some authors given a place wholly by themselves as a distinct group. This has been called by Professor Fraas the Thalattosuchia, a word meaning “sea-crocodiles.” They were a very early side-branch from the great genealogic
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CHELONIA
CHELONIA
No order of reptiles of the past or present is more sharply and unequivocally distinguished from all others than the Chelonia or Testudinata. No order has had a more uniformly continuous and uneventful history. None now in existence has had a longer known history, and of none is the origin more obscure. The first known members of the order, in Triassic times, were turtles in all respects, as well or nearly as well adapted for their peculiar mode of life as are those now living, and were they now
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SIDE-NECKED TURTLES. PLEURODIRA
SIDE-NECKED TURTLES. PLEURODIRA
The suborder of Chelonia, generally known as the snake-necked or side-necked turtles or tortoises, comprises about forty living species, confined to South America, Africa save the northernmost part, Madagascar, New Guinea, and Australia. In Australia they are the only members of the order known—another instance of the peculiar isolation of the fauna of that region. In the past they lived in North America during Upper Cretaceous times, the earliest known forms of the group in its restricted sense
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CRYPTODIRA
CRYPTODIRA
The chief families of the Cryptodira turtles are the Chelydridae, or snappers; the Emydidae, or marsh tortoises; the Testudinidae, or land tortoises; the Chelonidae, or sea-turtles; the Protostegidae, or ancient sea-turtles; and the Dermochelydidae, or leather-backs. Other doubtful or smaller groups, both living and extinct, may be omitted, or incidentally mentioned....
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SNAPPING TURTLES
SNAPPING TURTLES
The family of snapping turtles, the Chelydridae, are of interest because of their peculiar geographical distribution at the present time. Only four species are known, three of them from North America, the fourth from New Guinea. The family is one of the most primitive of living turtles, though no members of it are known with certainty from earlier rocks than the Oligocene. In all probability, also, they have retained, more than have any other group of turtles, unless it be some of the fresh-wate
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FRESH-WATER OR MARSH TORTOISES
FRESH-WATER OR MARSH TORTOISES
The family of turtles or tortoises (Emydidae) represented at the present time by the common terrapin, painted tortoise, and box tortoise of the United States, and commonly called fresh-water turtles or tortoises, comprises the largest group of living chelonians—nearly a third of all existing members of the order. They are widely distributed over all parts of the earth except Australia, and are of very varied habits. Some are almost exclusively aquatic; others, like the painted tortoise, are part
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LAND TORTOISES
LAND TORTOISES
Perhaps the last of the more noteworthy specializations of the Chelonia, and indeed among the last of the more important specializations of the Reptilia, are the upland tortoises, of which the common “gopher” of the southern states is almost the only remnant in North America. They formed a part of the great hegira of forest and marsh animals to the open prairies, away from the lowlands and water which the turtles had inhabited almost exclusively for millions of years. Fig. 118. — Testudo sumeire
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SEA-TURTLES. CHELONIDAE
SEA-TURTLES. CHELONIDAE
The sea-turtles, or Chelonidae comprise five or six living species, inhabitants for the most part of tropical and subtropical oceans, of which the green or edible turtle ( Chelone ), the hawksbill turtle ( Caretta ), and the loggerhead ( Eretmochelys [ Fig. 119 ]) are the best known. They are all thoroughly aquatic in habit, and of large size, from three to five feet in length. The carapace is heart-shaped, and reduced, that is, with large openings between the ribs; the plastron also is reduced
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ANCIENT SEA-TURTLES. PROTOSTEGIDAE
ANCIENT SEA-TURTLES. PROTOSTEGIDAE
Fig. 121. — Toxochelys latiremis ; front leg: hum , humerus; rad , radius; ul , ulna; int , intermedium; uln , ulnare; p , pisiform; cen , centrale. (From Wieland.) Fig. 122. — Desmatochelys lowii ; skull from above and below. Forty-four years ago the late Professor E. D. Cope, one of the greatest naturalists America has ever produced, in almost the earliest exploration of the great Cretaceous fossil deposits of western Kansas, discovered and collected a remarkable specimen of one of the most ex
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LEATHER-BACK MARINE TURTLES
LEATHER-BACK MARINE TURTLES
The most remarkable member of the Chelonia now living is Dermochelys coriacea ( Fig. 128 ), the great leathery or leather-back turtle of the warmer parts of the Atlantic, Indian, and Pacific oceans, the sole member of the family Dermochelydidae. It is the largest of all living turtles and the most thoroughly aquatic of all, whether living or extinct. It sometimes reaches a length of six feet, or half that of the largest known extinct forms, and weighs a thousand or more pounds. Agassiz saw a spe
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RIVER TURTLES. TRIONYCHOIDEA
RIVER TURTLES. TRIONYCHOIDEA
No reptile is more familiar or more exasperating to the river fisherman than the turtle, variously known as the river, soft-shelled, or mud turtle. It lives, often in great numbers, in most of the rivers, ponds, and bayous of the interior east of the Rocky Mountains, and especially in those of sluggish current and muddy bottoms. It is voraciously carnivorous in habit, feeding upon the smaller fish, mussels, and such other living food as it can capture. With its long, sinuous neck and snake-like
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