CHAPTER IV_Water Reptiles of the Past and Present

THE AGE OF REPTILES

Geologists divide the history of the earth, since life first appeared

upon it, into four general eras, the Proterozoic, Paleozoic, Mesozoic,

and Cenozoic, that is, into eras of first life, ancient life, middle

life, and recent life. These divisions were made long ago by geologists

when it was believed that extraordinary changes, great cataclysmic

revolutions, marked their limits.

With a fuller knowledge of the life of the past we know that evolution

has been continuous and uninterrupted; possibly accelerated or retarded

at times, but without break. Were the earth’s history to be written

anew, with our present knowledge, and with an unbiased mind, it is

very doubtful whether many of the time divisions would have the same

limits that they have now—whether the Paleozoic would terminate with

the Carboniferous, or the Permian, or the Trias, or whether indeed we

should think it necessary to make any primary divisions whatsoever. In

other words, our greater knowledge of living and extinct organisms,

and of the rocks which contain fossils, has made the problems of

classification much more complex than they seemed to be formerly.

It is much easier to classify organisms or rocks, or anything else,

when we know only a few isolated kinds—much easier to draw divisional

lines. Geological history is like a volume in which pages, leaves, and

even whole chapters either are missing or are printed in languages

which we understand only imperfectly. Where the lost or unknown parts

belong, the largest divisions may be made, and possibly such may have

been epochs of unusual activity, of diastrophic changes which greatly

accelerated organic evolution. No one can say just where the dividing

line should be drawn between the rocks of Paleozoic and Mesozoic age,

or between the Mesozoic and Cenozoic, for there is none; the most

that we can hope for is to make the divisions everywhere in the world

conform to those first made for local reasons.

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PALEOZOIC | MESOZOIC | CENOZOIC |

----------------------------+-------+--------+--------+----------+------+---------+-------+--------+------+-------

----------------------------+-------+--------+----+---+-----+----+------+---------+-------+--------+------+-------

PTEROSAURIA Pterodactyloidea| | |----|--████████████| | | | | |

| | | | | | | | | | | |

Pterodermata····| | |███████ ? | | | | | | |

| | | | | | | | | | | |

DINOSAURIA Theropoda·······| | ███████████████████████████ ? | | | | |

| | | | | | | | | | | |

Sauropoda·······| | | █████████ | | | | | | |

| | | | | | | | | | | |

Orthopoda·······| | |? ███████████████████ ? | | | | |

BIRDS ················| | | | ██████████████████████████████████████████████████████████████

| | | | | | | | | | | |

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Eusuchia········| | | ███████████████████████████████████████████████████████████████████

| | | | | | | | | | | |

PARASUCHIA Phytosauria·····| |████████| | | | | | | | | |

| | | | | | | | | | | |

Pseudosuchia····| | ███████| | | | | | | | | |

| | | | | | | | | | | |

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CEPHALIA ················| | █████ █ █ █ █████::|::::|::::::|:::::::::|:::::::|::::::::|██████████████

Choristodera····| | | | | | ████ | | | | |

| | | | | | | | | | | |

THALATTOSAURIA··············| | ███| | | | | | | | | |

Ophidia·····| | | | | | ██████████████████████████████████████████████████

| | | | | | | | | | | |

SQUAMATA Lacertilia··| | ███|::::|::████?::|::███████████████████████████████████████████████████

| | | | | | | | | | | |

| | | | | | | | | | | |

PROTOROSAURIA···············|████████::::::::|::::|████| | | | | | | |

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ICHTHYOSAURIA···············| | ██████████████████████████| | | | | |

| | | | | | | | | | | |

THEROMORPHA Caseasauria····|███ | | | | | | | | | | |

| | | | | | | | | | | |

Pelycosauria::███████████::::███|? | | | | | | | | |

| | | | | | | | | | | |

| | | | | | | | | | | |

Procolophonia··|█████████:::::::|::::|████|(Labidosauria) | | | | |

| | | | | | | | | | | |

Pareiasauria···|·██████| | | | | | | | | | |

██████████████████ | | | | | | | | | | |

==================================================================================================================

Pleurodira········| | ████████████████████████████████████████████████████████████████████████

CHELONIA Cryptodira········| | | |███████████████████████████████████████████████████████████████

| | | | | | | | | | | |

Trionychoidea·····| | | | | | █████████████████████████████████████████████████

SAUROPTERYGIA Nothosauria···| | █████ | | | | | | | | | |

| | | | | | | | | | | |

Plesiosauria··| | ██████████████████████████| | | | | |

| | | | | | | | | | | |

Dromasauria | ████ | | | | | | | | | | |

| | | | | | | | | | | |

Dinocephalia | ████ | | | | | | | | | | |

| | | | | | | | | | | |

THERAPSIDA Anomodontia | ████████████| | | | | | | | | |

| | | | | | | | | | | |

Therocephalia | ████ | | | | | | | | | | |

Theriodontia | | █████ | | | | | | | | | |

MAMMALS·····················|· | ██|::::|:██████:::|:███████████████████████████████████████████████████

----------------------------+-------+--------+----+----+-----+---+------+---------+-------+--------+------+-------

FIG. 23_a_.—Range of the Reptilia. Heavy lines indicate occurrence in North America.

The periods of the Paleozoic era are the Cambrian, Ordovician,

Silurian, Devonian, Carboniferous, and Permian, in the order as given;

those of the Mesozoic era are the Triassic, Jurassic, and Cretaceous;

those of the Cenozoic era, the Eocene, Oligocene, Miocene, Pliocene,

Pleistocene, and Recent. As a relic of an old classification we still

often divide the Cenozoic into two quite arbitrary divisions, the

Tertiary and the Quaternary, the latter including the Pleistocene and

Recent only. The same may be said regarding the limits of each of

these periods as of the eras; the sole problem is to make each period

contemporaneous throughout the world, an exceedingly difficult problem,

because no faunas or floras have ever been the same over the whole

earth. Indeed, with the exception of some of the lowliest and most

generalized forms, or man himself, no species are the same throughout

the earth today. Inasmuch as we must depend upon the fossils in the

rocks for the determination of the ages, where none is quite the

same in strata of remote localities the identification becomes very

difficult or even impossible. Nor are the periods, as accepted, of

equal or even approximately equal duration; the Cretaceous period, for

instance, was longer than all the remainder of the Mesozoic, longer

perhaps than all the time which has elapsed since its close.

The earliest animals with a backbone, or rather the earliest that we

call vertebrates—for some vertebrates have no vertebrae—began their

existence, so far as we know, in late Ordovician times, as attested

by fish bones in Ordovician rocks of Colorado and Utah. The first

evidences of the existence of air-breathing vertebrates in geological

history are footprints preserved in the uppermost Devonian rocks of

Pennsylvania. We call them amphibian because they resemble footprints

associated with amphibian skeletons in later formations, and because

the foot itself is still the most important difference we know between

fishes and the higher animals.

[Illustration: FIG. 24.—Permocarboniferous landscape (adapted from

Neumayr) with restoration of _Eryops_, a stegocephalian amphibian

ancestrally allied to the reptiles; and _Limnoscalis_, a cotylosaur (in

water).]

In the rocks of the next great time division, the Mississippian, as we

call it in America, corresponding more or less closely with the Lower

or Subcarboniferous of other parts of the world, numerous footprints

of amphibians have been discovered, but no fossil remains except a

few from near its close in Scotland. From the Upper Carboniferous, or

Pennsylvanian, however, not only numerous footprints but the actual

skeletons, or impressions of skeletons, have long been known in Europe

and America. Until recently all these footprints and skeletons were

supposed to be exclusively amphibian. We are now almost sure that some

of them belonged to reptiles of lowly type, the earliest coming from

near the middle of the Pennsylvanian of Linton, Ohio. The amphibians of

this period were, for the most part, salamander-like creatures of from

a few inches to two or three feet in length. They all belong to the

group collectively known as the Stegocephalia, except that very near

the close of the period there appeared small, slender, small-legged

aquatic forms which seem to be the ancient representatives of the real

salamanders of modern times. Some of the Stegocephalians had become

greatly specialized as legless, snake-like, or eel-like creatures.

[Illustration: FIG. 25.—Restoration of _Seymouria_, the most primitive

of known cotylosaur reptiles. From the Permian of Texas, about two feet

long.]

By the beginning of Permian times tremendous changes had taken place

in the land life. The small amphibians of the Carboniferous types

dwindled away, soon to disappear, and their places were taken by others

of peculiar types, for the most part larger; and by many and diverse

kinds of reptiles—water reptiles, marsh reptiles, land reptiles, and

even climbing tree reptiles. From the uppermost Carboniferous and

Lower Permian rocks of the United States more than fifty genera and

twice that many species of amphibians and reptiles have been made known

in recent years, and doubtless as many more will be discovered in the

future. From other parts of the world the history of reptiles of the

Lower Permian is yet scanty, two or three forms from South America, as

many more from Africa, and a half-dozen or so from Europe are all; and

of these very few are known at all well.

[Illustration: FIG. 26.—_Captorhinus_, a cotylosaur reptile from Texas.]

We classify all the known forms of reptiles from the Lower Permian

under three or four orders, the Cotylosauria, Theromorpha or

Pelycosauria, Proganosauria, and possibly the Protorosauria, but the

classification is yet provisional, representing merely the present

stage of our knowledge. The Proganosauria and Protorosauria, including

distinctively aquatic reptiles, will be more fully described in

the following pages. To give even a brief description of the more

terrestrial reptiles of this, the earliest known reptilian fauna, would

be beyond our purpose; the accompanying life restorations by the author

of some of the more typical and better known forms, based upon nearly

perfect skeletons, will suffice.

From the reptiles and amphibians of the Lower Permian of Texas and New

Mexico to the ichthyosaurs of the Middle Triassic of California there

is a complete gap in the records of the land life of North America. We

do not know what became of all the remarkable animals of the Permian.

There are few traces of their descendants elsewhere known, unless it

be in South Africa. From the Middle and Upper Permian of South Africa

and Russia, a marvelous reptilian fauna has been made known in recent

years. More than a hundred species of six or seven groups, and at least

two orders have been described. Of these the Cotylosauria are the

continuation of the American order, but include more specialized forms,

the Pareiasauria and the Procolophonia, all of them, like the more

primitive American forms, characterized by the imperforate temporal

region. The Therapsida, likewise, seem to be the continuation of the

American Theromorpha, so closely allied to them that it is difficult

to draw a distinguishing line between them. On the other hand, these

African reptiles merge through the Theriodontia into the mammals in the

Triassic. They are all terrestrial, crawling reptiles, except a few

which are described on a later page under the Anomodontia.

[Illustration: FIG. 27.—Restoration of _Labidosaurus_, a cotylosaur

reptile from Texas, about three feet long.]

The records of the lower part of the Triassic period are scanty

everywhere in the world, save perhaps in Africa. Before the close of

the period, however, probably every important group of cold-blooded

air-breathing animals had made its appearance in geological history,

if we except the snakes; even the mammals had appeared, and possibly

the birds. The Cotylosauria, Theromorpha, and Therapsida disappeared,

the latter giving birth to the mammals; the nothosaurs and plesiosaurs,

the ichthyosaurs, dinosaurs, crocodiles, phytosaurs, rhynchocephalians,

lizards, and turtles have all left records of their existence in Upper

Triassic rocks; and the pterodactyls had also, in all probability,

begun their career, though none is surely known till the Jurassic.

During Jurassic times all these orders of reptiles waxed prosperous

and powerful, and branched out in many ways and in countless numbers;

many new kinds of each appeared—the marine crocodiles, the quadrupedal

dinosaurs, etc.—but no order or suborder, so far as we know,

disappeared before its close. And this prosperity continued on into

the Lower Cretaceous and for many even into the Upper Cretaceous. The

largest dinosaurs disappeared in the Lower Cretaceous, so far as our

knowledge goes, but the old-fashioned crocodiles continued on into

the Upper, to give place to the new-fashioned kinds. The ichthyosaurs

lingered on for a while on the western continent, but the mosasaurs

appeared, and the plesiosaurs reached their highest evolution and

continued to the end. The flying reptiles attained the zenith of

their evolution, but disappeared before the close. The marine turtles

attained the maximum of specialization and size. The upright-walking

dinosaurs continued on unabated to the close of the period; and a new

kind of dinosaurs appeared near the end.

[Illustration: FIG. 28.—Restoration of _Dimetrodon_, a pelycosaur

reptile from the Permian of Texas; about eight feet long.]

With the opening of the next great era—the Cenozoic or Tertiary—the

reptiles dwindled away to their present insignificant position, while

the birds and mammals appeared in great numbers and varied forms. The

Age of Reptiles was closed and the Age of Mammals had begun.

The history of the reptiles during the Cenozoic is an uneventful one;

they ceased their dominion upon land, in the water, and in the air.

Their remains are scanty, for the most part, in the rocks of the

Tertiary, and such as are known differ only in details from those now

living. The land tortoises only, like the mammals of Oligocene and

Miocene times, seized the opportunities of open prairies and prospered.

A few of the late Mesozoic forms continued a short while into the

Eocene. No new groups, perhaps few new families, came into existence

during the greater part of this time; it was the age only of land

tortoises and the poisonous snakes among reptiles.

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 precise relationships of the animal must

remain doubtful.

The next later rocks that have yielded reptilian remains are those

of Illinois and Texas formerly supposed to be of Permian age. Later

evidence, furnished by invertebrates, however, seems to prove that

the lowermost of the strata are of uppermost Carboniferous age. The

Illinois deposits, so far as known, are of very limited extent,

consisting practically of a single bone-bed in black shale in the

immediate valley of the Kaskaskia River near Danville. The known

fossils from this bone-bed—all isolated bones—are preserved in the

museum of the University of Chicago, and include the types of several

genera later recognized in the Texas deposits.

The deposits of Texas, extending northward through Oklahoma to the

south line of Kansas, are of considerable extent, for the most part

lying along the Wichita River and its tributaries, north of Seymour,

Texas. They are composed chiefly of red clays and sandstones of

fresh-water or delta origin, perhaps eight hundred feet in total

thickness. Beds of like character and yielding similar fossils are also

known from northern New Mexico on the tributaries of the Chama River.

Their chief characters, as well as restorations of some of the more

noteworthy forms, have already been given.

No vertebrate fossils are known in America from the Upper Permian and

Lower Triassic. Marine limestones of Middle and Upper Triassic age

of Nevada and northern California have yielded numerous remains of

primitive ichthyosaurs, the only known remains of the thalattosaurs,

and a few others of doubtful affinities, all of which have been

described by Dr. Merriam. The Upper Triassic exposures, of considerable

extent, occur between the Pitt River and Squaw Creek in Shasta County,

California. Reptilian remains from the Middle Triassic are so far known

only from the limestones of West Humboldt and New Pass regions of

western and central Nevada.

[Illustration: FIG. 29.—Restoration of _Varanops_, a theromorph reptile

from the Permian of Texas; about four feet long.]

Land reptiles of Middle and Upper Triassic age are known from many

widely separated localities in the United States, but chiefly from

the extensive “red beds” of the Rocky Mountain region. The fossils

from these beds occur for the most part at least in the horizon called

the Shinarump. Its age is usually considered to be Upper Triassic,

but the character of the fossils seems to indicate possibly the

Middle Triassic. Aside from the stereospondylian amphibians, the last

of the Stegocephalia, the vertebrates from this horizon and these

regions are chiefly Phytosauria. A few anomodonts, or what seem to be

anomodonts—the only record of their occurrence outside of Africa—are

known from Wyoming and Utah. And a single specimen from the Wind

River red beds, described by the writer as _Dolichobrachium_, may

represent reptiles allied to the dinosaurs. Phytosaur fossils of this

horizon have been discovered in Utah, the Wind River Mountains, and

near Laramie City in Wyoming; in southwestern Colorado; in western

Texas; and in various places in New Mexico and Arizona. Doubtless when

these fossiliferous beds are more thoroughly explored many new and

interesting reptiles will be discovered.

Phytosaur remains, probably of about the same age as the Rocky Mountain

ones, have long been known from the Triassic of North Carolina.

From somewhat more recent Triassic deposits in Connecticut and

Massachusetts, several skeletons of small carnivorous dinosaurs, and

various parasuchian remains have been described by Marsh, Lull, and

Talbot. And these beds have long been famous in Massachusetts for their

footprints, for the most part originally referred to birds, but now

pretty well known to have been made by dinosaurs and amphibians.

No vertebrate fossils of Lower or even Middle Jurassic age are known

from North America. From the Baptanodon beds of Wyoming, limestones of

about two hundred feet in thickness, four genera of plesiosaurs, the

very peculiar ichthyosaur from which the beds take their name, and a

few bones of an ancient crocodile are known.

Immediately overlying the Baptanodon beds, the Morrison beds, of from

two hundred to four hundred feet in thickness, probably of Uppermost

Jurassic and Lowermost Cretaceous age, have yielded an exceedingly rich

vertebrate fauna, consisting chiefly of dinosaurs. Discovered first in

the vicinity of Morrison, Colorado, in 1877, hundreds of tons of bones

have been collected from these beds for various museums. The dinosaurs

include many genera of all three suborders, varying in size from that

of a cat to some of the largest known land animals. Of other reptiles a

very few jaws of a true rhynchocephalian, a fragment of a wing bone of

a pterodactyl, numerous turtles, and crocodiles, only, are known. The

beds are predominantly black-clay shales, intercalated with sandstones,

and all are of fresh-water origin.

From beds definitely known as Lower Cretaceous (Trinity) in Oklahoma,

a few bones of a sauropod dinosaur are known, and from nearly

corresponding rocks in southern Kansas, plesiosaurs, crocodiles,

turtles, and carnivorous dinosaurs are known from sparse remains.

Doubtless the Potomac beds of Virginia, which have yielded bones of

various dinosaurs, are also of Lower Cretaceous age.

[Illustration: FIG. 30.—Restoration of _Casea_, a theromorph reptile

from the Permian of Texas, about four feet long.]

With the exception of a single vertebra of doubtful affinities and

the cast of a turtle-shell no vertebrate fossils have ever been

discovered in the extensive sandstones of Dakota age, the lowermost

of the Upper Cretaceous. From the next horizon above the Dakota, the

Benton Cretaceous, chiefly marine limestones, at least three genera

of plesiosaurs are known from Kansas, Texas, and Arkansas, with two or

three more from the limestone shales of Wyoming. A few specimens of

armored dinosaurs, two genera of ancient crocodiles, nearly the last of

their kind, some marine turtles, and a few vertebrae of ichthyosaurs,

the last of the order known anywhere in the world, are also known from

the Benton Cretaceous of Wyoming.

Continuous with the Benton limestones above in Kansas are the famous

beds of Niobrara chalk; perhaps no fossil deposits in the world are

more famous. Exposures covering hundreds of square miles in western

Kansas, almost pure chalk, have furnished fossil-hunters during the

past forty years literally thousands of specimens of mosasaurs,

hundreds of pterodactyls, and scores of plesiosaurs and marine turtles,

in addition to the famous birds with teeth and countless fishes of

diverse kinds. Two or three specimens of spoon-billed dinosaurs have

been found in these deposits, but no other reptiles of any kinds. Beds

of like age in Colorado and New Mexico have furnished a few specimens

of mosasaurs.

From the marine beds of Fort Pierre age, next above the Niobrara in the

west, have come some excellent specimens of two genera of mosasaurs,

three or four forms of plesiosaurs, a few pterodactyls, the largest of

all marine turtles, and still fewer specimens of dinosaurs, in Kansas,

South Dakota, Wyoming, and Montana. From deposits of approximately like

age in Mississippi, Alabama, and New Jersey, many incomplete specimens

were found years ago of mosasaurs, plesiosaurs, and turtles, the last

of the amphicoelian crocodiles, the first of the procoelian crocodiles,

and the famous specimen of _Hadrosaurus_ which served for the Hawkins

restoration, the first attempt of its kind.

From the uppermost Cretaceous beds of America, the Lance, Judith

River, or Belly River beds as they are variously called, have come

the remains of a marvelous reptilian fauna. These beds may be grouped

together though not all contemporaneous, and there is dispute about

their age, some excellent paleontologists insisting that the uppermost

are really of Eocene age. From Colorado east of Denver, from eastern

Wyoming, from Montana, and especially from the vicinity of Edmonton

in Canada, as also occasionally in western Texas and New Mexico,

have come many marvelous specimens of dinosaurs, huge bipedal

carnivorous dinosaurs, great spoon-billed aquatic dinosaurs, armored

stegosaurian dinosaurs, and many kinds of the great horned dinosaurs,

the Ceratopsia, so far known only from these beds. Here at the very

close of the Age of Reptiles, at the close of the Age of Dinosaurs,

are found the ultimate specializations of all the chief groups of

dinosaurs except the long-necked quadrupedal dinosaurs which gave up

the ghost in Lower Cretaceous times. Many were provided with horns and

spines, some indeed seemed to have bristled with spines throughout,

a sure sign that they were approaching the end of their career. The

modern type of crocodiles had usurped the ancient forms of the early

Cretaceous, and reached the largest size of their race perhaps, though

but few specimens are known. Here also in these beds we find the

first representatives of lizards and snakes in America, though snakes

have been described from earlier strata, perhaps, in Brazil. Those

archaic, old-fashioned rhynchocephalians described on a later page as

the Choristodera appeared also for the first time in these beds, and

persisted for a little while in the Eocene, in Europe and America. And

with all these there has very recently been described the last of the

plesiosaurs, whose race went out with the dinosaurs at the very close

of the Mesozoic. It is needless to say that the turtles also occur,

for, as a general rule, wherever vertebrate fossils are found, in rocks

of the land or the sea, marine or fresh-water, there will be some bones

of turtles among them.

With the beginning of the Cenozoic the record of the reptiles

becomes relatively scanty in America. In the warm waters of the old

Eocene lakes and rivers of Wyoming lived countless crocodiles, true

crocodiles of modern aspect and of large size. But, as the climate

of North America grew progressively colder, the crocodiles retreated

to the south, till, in the Oligocene, the scanty remains of the last

crocodiles are found in the American Tertiary. On the other hand, as

the open lands appeared toward the close of the Eocene, and in the

Oligocene and Miocene, the land tortoises throve and grew greatly in

size. In the Bad Lands of South Dakota one may see their remains in

almost incredible numbers. And in equally great numbers are these land

tortoises, in shape much like the common box tortoise of today, but

vastly larger, found in the rocks of the late Miocene or early Pliocene

age in western Kansas. And these are the last records of the big

tortoises in North America; their descendants are perhaps yet living in

the Galapagos Islands.

The history of the lizards and snakes, the only other reptiles found

in the Cenozoic rocks of America, is very brief. A few specimens from

the Lower Eocene of Wyoming; a few skinks and amphisbaenas from the

Oligocene Bad Lands of South Dakota, and some bones of a python-like

snake in the early Eocene of Wyoming are about all that we know of the

Squamata in the Tertiary. Doubtless snakes and lizards were just as

abundant then as now, though but few were preserved, for they are and

always have been distinctly terrestrial animals, that only by accident

fell into places where they could be fossilized.

The author has collected reptile bones from nearly all of the horizons

here mentioned and believes that the list is complete.