TEN CENT POCKET SERIES NO. 274
Edited by E. Haldeman-Julius
Animals of Ancient
Lands
Carroll Lane Fenton
Author of “Animals of Ancient Seas,”
“The Building of the Earth,”
“A History of Evolution,” Etc.
HALDEMAN-JULIUS COMPANY
GIRARD, KANSAS
Copyright, 1922,
Haldeman-Julius Company.
LIST OF ILLUSTRATIONS
Page
Fig. 1 8
Fig. 2 10
Plate I. 12
Plate II. 13
Plate III. 17
Plate IV. 24
Plate V. 26
Plate VI. 29
Plate VII. 32
Plate VIII. 36
Plate IX. 39
Plate X. 45
Plate XI. 47
Plate XII. 63
INTRODUCTION.
This volume of the evolution series of the pocket library is, like its
predecessors, an expansion of a lecture which the author has frequently
given before popular audiences. It differs from its immediate
predecessor in that it is more loosely planned, and less obviously
designed to instruct. Geologic tables and explanations have been
omitted entirely; these the reader can secure from the volume in this
Series (No. 47) entitled “Animals of Ancient Seas,” while something
about fossils and their origin is given in the first chapter of “The
Building of the Earth.” (No. 275.)
The lecturer is more fortunate than the writer in that his
illustrations are more numerous; indeed, a good stereopticon lecture
need be little more than a collection of beautiful and accurate slides
interestingly described. However, the publishers have been generous
in the number of illustrations used in these booklets, so that the
difficulty is in a measure overcome.
It remains for me to acknowledge my indebtedness to the various
authors and articles mentioned in the text and in notes. Dr. Lucas’
excellent and interesting book, “Animals of the Past,” has afforded in
a concise form much information that otherwise could have come only
from scattered technical papers. The article by Dr. Case has furnished
the base for the entire first chapter, much of the material being
reproduced with but the slightest changes in wording and arrangement,
with the omission of some technical data. Professor Case’s position as
our principal authority on Permian vertebrates gives this chapter a
reliability that could not be achieved by a second-hand re-writing of
material from his larger and more detailed monographs.
C. L. F.
CHAPTER I.
THE FIRST LAND DWELLERS.
In the first book of this series, “Animals of Ancient Seas,” (No.
47) we followed the evolution of animal life from the most primitive
one-celled creatures to the fishes, and from the most primitive
fishes to those which possessed lung-like organs that enabled them
to breathe from air as well as water. The next stage in evolution
was the development of feet and legs from the fish fin, and this was
accomplished before the end of that geologic period known as the
Devonian, or more commonly, as the “Age of Fishes.” True, no actual
remains have been found, but one fortunate collector succeeded in
getting out a fossil footprint, which is all that is needed to prove
the case. This footprint was made by an animal that looked much like
the mud puppy, or salamander, of modern streams and lakes, and was
related also to the frogs and toads. Like these creatures, he spent the
early part of his life in water, breathing with gills, and possessing
a more or less fish-like form, while in his maturity he lived at
least partly on land, and breathed by means of lungs. This type of
development, almost universal among his class, has gained for them the
name of Amphibians, or “double livers.”
During those periods which are correctly known as the Mississippian
and Pennsylvanian, but which are more commonly grouped under the one
name Carboniferous, the amphibians increased in variety, and gave
rise to a new and immensely important group of animals, the Reptiles.
Since everyone knows the general characters of this group, we shall
not take the trouble to define them. The important thing about them,
so far as evolution is concerned is that they are capable of living
on land throughout their whole lives, not even the eggs having to be
deposited in water. This, as can readily be seen, is a very fundamental
character, for as long as animals were confined to water during their
earliest stages, great progress was quite impossible. Imagine what a
state humanity would be in if every child had to begin life in some
brook, lake, or pond, and could not emerge from the water until it was
fifteen to twenty years old!
Unfortunately for our knowledge of life in the past, fossils of both
amphibians and reptiles are by no means common in the Carboniferous
systems. It was not until the times of coal deposition were almost
past, and great mountains and broad plains were taking the place of
shallow seas and sombre swamps, that land dwelling animals became
really abundant. This appearance of dry land was not only the cause of
the development of the wonderful array of animals that inhabited the
Permian world, but also the reason why so few of them are preserved
as fossils, for it is only when the bones of animals become buried in
water-soaked layers of sediment, or covered by water, that they are
readily petrified. An animal that dies and remains exposed to the
open air stands very little chance of becoming a fossil; its bones are
gnawed by carrion feeders, worn by the wind, and broken up by decay.
Thus of the hundreds of thousands, even millions, of buffalo, cattle,
antelope, and elk whose carcasses have dotted the plains of this
continent in the past half century there remain but a few rotten and
frost-split horns and bones. Without question there are, in the muddy
banks and bars of rivers, skeletons and parts of skeletons that are
undergoing the slow process of petrification, and that will be dug up
and treasured in the museums of some future civilization. And just as
the record of animal life of today will be but a fragment of that which
actually exists, so the record of the great land fauna of the Permian
period is but the merest trace of the myriad creatures of that time. It
is only in the most exceptional places that great quantities of bones
were brought together under conditions favorable to fossilization, and
such a district is found in northern Texas.
“When the Appalachian Mountains were raised, an extension of their
southern end reached across what are now Arkansas and Oklahoma,
terminating in the Wichita Mountains.... North of this range rose a
broad upland, reaching from the Rockies to the Appalachians and to
the Canadian line on the north; south of the mountains a shallow sea
reached nearly to their base, and some great rivers from the mountains
and uplands poured their flood waters into the sea and built up a
great delta. The remains of animals which haunted the banks of the
rivers were swept into them in time of flood and carried out to be
deposited in the delta, which covered most of what is now Wichita,
Archer, Wilbarger counties in the State of Texas. Naturally, most
of the remains which found their way into the streams were already
fragmentary, as they had rotted on the banks, and had been torn by
predatory animals, but in their course to the sea they were still
further disintegrated so that, rolled by the waters and beaten by
the waves, they sank to their burial as little more than water-worn
fragments; ends of limb bones, isolated vertebrae, and broken skulls,
which do little more than tantalize the student with the hints of new
forms and new relationships that can not be verified. In some places
these water-worn fragments are so thick upon the ground that they
literally can be shoveled up by the wagon load. In some instances
the bodies of animals found their way unharmed into the water and,
distended by the gases of decomposition, floated far and uninjured
until they came to rest on some mud flat beyond the reach of sharks
or other predatory animals. Such skeletons are preserved entire with
most remarkable perfection, but they are exceedingly rare, and it is
a fortunate collector who turns up even one in the course of a whole
season of search.”[1]
[Illustration: FIG. 1
Cacops, a remarkable Permian amphibian.]
Among the most remarkable of the animals found in the stratified rocks
of this ancient delta are the amphibians. During the preceding ages,
as we have seen, they were the masters of the continental world--the
largest and most progressive of land dwellers. But by the time of
the Permian they were on the downward road which was to lead them,
not to extinction, but to the obscure positions of toads, frogs
and salamanders. But this decline did not come at once, and with
overwhelming completeness; the early amphibians did not yield tamely to
the fate of old age. During the Permian, and the succeeding age, the
Triassic, there lived some of the largest and strangest amphibians that
the world has known. Some of them returned to the water and developed
eel-like bodies with enormous, arrow-like heads; some lived in trees,
where their remains have been found by geologists studying coal
deposits; others protected themselves by armor and crawled about more
or less unmolested, while not a few even went so far as to take refuge
in the ground.
The giant among all amphibians was Eryops, of the Permian, with a
length of about eight feet. He looked somewhat like an immensely
overgrown salamander with flabby sprawling legs that were incapable of
lifting his body from the ground except by the greatest effort. His
skull was from two to two and a half feet in length, and looked like
that of a gigantic frog, the jaws were equipped with sharp, cone-shaped
teeth and sharp, powerful tusks. Evidently Eryops held about the same
position in Permian swamps of Texas as the alligator does in the
Georgia bayous of today, lying near the surface of the water with only
its eyes and nostrils exposed until the approach of a victim stirred it
to movement.
Sharply contrasted with the giant Eryops, and doubtless often its
victim, was the unique Diplocaulus. The head of this amphibian was
the form of a rather angular crescent, with strong spines directed to
the rear, and protected by heavy armor. The eyes and nostrils were
directed straight upward, and situated at the forward end of the skull.
The body, remarkably enough, was long, thin, and eel-like, with only
rudimentary limb bones, and delicate ribs. Probably the animal spent
its entire life in the water, wriggling along and pushing its enormous
head before it along the slimy bottom. Perhaps, when attacked from
above, Diplocaulus was thrown into a frenzy of energy that lifted his
heavy, armored head above the bottom, and thrashed it about in the
water, but anything like swimming must have been quite beyond his power.
[Illustration: FIG. 2
Diplocaulus, the most bizarre amphibian known.]
But, bizarre though the amphibians of this Permian deposit are, they
are exceeded by the reptiles. These creatures, as we have seen, made
their appearance in the Pennsylvanian, or late “Carboniferous,” and
already, in the very beginning of their history, they showed an
astonishing diversity of form and habit. There were reptiles that
lived in the water, and reptiles that lived on dry land; reptiles that
ate flesh, reptiles that ate plants, and reptiles that ate both. Some
of them were extremely primitive, closely resembling their amphibian
ancestors, while others were like nothing that has lived either before
or since.
The simplest of the flesh-eating reptiles were aquatic, living in the
waters of swamps and rivers, and perhaps even in the sea. Their bodies
and tails were long and slender; their teeth were simple, cone-shaped
affairs of almost equal size throughout the entire length of the jaw.
Such a dentition indicates that the reptiles possessing it preyed upon
small animals which they did not have to tear to pieces; they merely
seized their food and swallowed it, leaving the entire process of
digestion to the internal organs, just as do the snakes of today. The
upper portions--called dorsal spines--of the backbones in these forms
were short, as they are in most lizards, and did not project through
the skin.
In other, and somewhat higher reptiles, the teeth appear to be
differentiated, those at the forward ends of both jaws being enlarged
to form tusks, while the posterior ones are flattened, so that cutting
edges are developed that would cut the prey and assist materially in
its capture. In some of these same forms the dorsal spines of the
backbones are very high, and project above the back as does the fin of
a fish.
In Dimetrodon, the last of the series of spiny backed, carnivorous
reptiles, these characters reached their culmination. The incisor and
canine tusks attained an enormous length and strength, projecting
from the jaws as much as three inches. The notch back of the incisors
is large and deep, and the posterior teeth of both jaws are recurved
and have sharp, serrated edges so that they must have had all of the
cutting power of a Malay knife or _kris_. A more effective set of
weapons for the cruel business of capturing prey and holding it despite
its desperate, agonized struggles hardly could be conceived. At the
same time, the spines on the back developed to an enormous length,
and in some species tapered with the delicacy of a whip lash. The tail
was short and strong, and the feet armed with well-developed claws,
all of which go to show that the animal was purely land dwelling in
habit. Dimetrodon reached lengths of more than eight feet, and was by
all odds the largest and most powerful creature of his day. We can
imagine him crouching in the bushes or tall grasses by the side of some
stream, watching for other reptiles that come to quench their thirst,
and making a fierce, scuttling rush upon his prey. Most often, perhaps,
this was another reptile, but the ponderous, slow-moving amphibians
also must have suffered from the attack of the powerful Dimetrodon.
There is ample evidence that these animals often waged fierce battles
among themselves, for it is common to find bones which have been broken
during life and healed again, telling of furious reptilian contests
for mates or territory, or perhaps with the single brute idea of a
cannibalistic meal.
[Illustration: PLATE I.
Restoration of Dimetrodon, the largest animal of the Permian lands.]
[Illustration: PLATE II.
Naosaurus (Edaphosaurus), the profusely spined mud-grubber. (After
Case.)]
But a more wonderful animal still has left its remains among the rocks
of this delta. Like Dimetrodon, it possessed high spines on the back,
but instead of being simple and tapering, they were furnished with
projecting processes on either side, much like the yard arms of old
fashioned sailing ships. This resemblance led Cope, a pioneer American
paleontologist, to call the animal Naosaurus, or “Ship Lizard.” But in
spite of his fierce appearance, Naosaurus was totally unlike Dimetrodon
in habit, being a peaceful, sluggish eater of shellfish, and perhaps
of plants. This animal probably has the most remarkable dentition of
any creature known. The incisor teeth are chisel-like, as though
useful in cutting strong, coarse vegetation; behind them are five
triangular teeth not unlike those of such flesh-eaters as the lion
and tiger; behind these are simple cones, like those of the primitive
lizards. But, most wonderful of all, on both the palate and the
corresponding portion of the lower jaw are heavy plates of bone covered
by short, stumpy teeth, such as occur in the jaws of those fish which
live upon shellfish. Seemingly, therefore, the animal ate all sorts of
food, but instead of having a generalized pattern of teeth like the pig
or man, it possessed a separate set for each type of diet.
The discovery that Naosaurus was an eater of plants and molluscs, and
not a predatory form, makes more perplexing than ever the question as
to the use of the spines on the back. On such a thick-bodied, sluggish
mud-grubber the cross-barred spines must have had about the same value
as an ornamental frieze on a canal boat. What conditions of environment
could have produced similar structures on creatures of such dissimilar
habits as Dimetrodon and Naosaurus?
The structure of the animal shows that these spines were not covered by
flesh, but by a thin membrane of skin, through which the spines showed
as plainly as the rays in the fin of a fish. It is hard to conceive
of this great dorsal frill as being anything but a hindrance to both
pursuer and pursued. Cope suggested, in a spirit of fun, that these
animals were the natural precursors of the modern fin-keeled yacht,
and that when they wished to navigate the Permian waters they swam
upon their backs. Other authors have made other suggestions of about
the same note, but few have been able to make any serious contribution
on the subject. The obvious suggestion is that the spines served as
some form of protective mimicry, helping the animal to remain concealed
among the reeds which bordered the lakes or streams. But this seems
hardly necessary in an animal that was the dominant form of its time
and needed no concealment unless as an aid to lying in wait or making
an unseen approach until sufficiently near for its final rush upon
its unsuspecting prey. This last, is perhaps, a fair suggestion, but
it seems that the burden of maintaining such a weak structure must
have far outweighed any advantage of concealment. The spines were
slender and were constantly being broken in battle and by accident, and
the animal must have expended no inconsiderable amount of energy in
repairing the damaged structure.
There remains the suggestion that the spines were remnants of a
formerly useful structure, and that their mature condition was purely
due to overgrowth. It seems certain that when a structure has developed
so far as to give an animal a distinct advantage it may continue
to grow until it is a burden rather than a help. Thus the spines,
originating as a protective feature, may have given their possessors
such a decided advantage that they were almost free from attack. In
this stage they may have become over-nourished, and have continued
growing by a sort of inertia or momentum until they reached their
greatly exaggerated development.[2] Furthermore, there is a tendency,
both in plants and in animals, for a species nearing its extinction
to develop a spiny or horny habit. This we saw in the invertebrates,
among the aging Cephalopods, and it is quite conceivable that a similar
state of affair prevails among these reptiles. For Dimetrodon and
Naosaurus,[3] dominant though they were, were nearing the end of their
life cycle. In their senile aberrations they carried the development
of spines to greater and greater lengths, until, in their declining
strength they were unable to maintain their species, and so disappeared
from the earth.
[Illustration: PLATE III.
Permian vertebrates, restored by Williston and others. 1-3 are
reptiles, while 4 is an amphibian.]
FOOTNOTES:
[1] Case, E. C., “A Great Permian Delta and its Vertebrate Life,” Pop.
Sci. Monthly, Dec. 1908. This quotation is somewhat paraphrased, while
the remainder of this chapter is based very largely on the article.
[2] Paraphrased from Case, Loc. Cit.
[3] A relatively recent discovery, made by Dr. Case, shows that the
name Naosaurus must be dropped, being replaced by the earlier name
Edaphosaurus. The former name, however, is the commoner, as well as the
more descriptive.