SOME AMERICAN MONSTERS.
"Geology, in the magnitude and sublimity of the objects of
which it treats, ranks next to Astronomy in the scale of the
Sciences."--Sir John F. W. Herschel.
With the advent of the Cainozoic or Tertiary era, we enter upon the
"Age of Mammals," when great quadrupeds suddenly came upon the scene.
The place of the reptile was now taken by the mammal. In the long
previous era this higher type of life was not altogether wanting, but
as far as the geological record is yet known, it appears only to have
been represented by a few primitive little creatures, probably
Marsupials, whose jaw-bones have been discovered in the New Red
Sandstone, and the Stonesfield Oolite.[39]
[39] The English Cretaceous rocks, previously thought to be destitute
of mammalian remains, have quite recently yielded teeth belonging to
some small mammal. These were found in Wealden strata.
Geology tells of a great gap between the highest rocks of the
Cretaceous period and the lowest group of the succeeding Eocene period
(see Table of Strata, Appendix I.). This gap, or break, testifies to a
very long interval of time during which important geographical and
other changes took place; and consequently we find in Eocene rocks (at
the base of the Cainozoic series) a very different fauna and flora to
that which is preserved in the Chalk formation.
The researches of Cuvier among the fossils collected from Eocene rocks
in the neighbourhood of Paris, especially the Gypseous series of
Montmartre, revealed the existence of a very extensive fauna,
especially of new types of mammals; and his restoration of the
Palæotherium, a tapir-like animal, and other forms, created a vast
amount of interest, and greatly stimulated the study of extinct
animals. As we have already remarked, the science of palæontology may
be said to have been founded by Cuvier (see Introduction, p. 5).
But now the scene shifts once more from Europe to the wilds of the Far
West. American geologists tell us that a long time ago (during the
Eocene period) there was a great tropical lake in the Wyoming
territory, on the borders of which roamed, amidst luxuriant
vegetation, a large number of strange and primitive quadrupeds,
together with many other forms of life. The most wonderful group of
animals that haunted the shores of this lake, or series of lakes, was
the Dinocerata so fully described by Professor Marsh, in his
exhaustive monograph.[40] The name implies that they were terrible
horned monsters, but whether Nature provided them with true horns,
like those of horned cattle to-day, is at least open to doubt.
[40] _The Dinocerata_, a monograph by O. C. Marsh, _United States
Geological Survey_, vol. x.
Fig. 42 shows the skeleton of one of these, namely, Tinoceras ingens.
Its length was about 12 feet without the tail. Its weight, when alive,
is calculated to have been six thousand pounds, or about two tons and
three quarters.
Plate XIV. is a restoration of the Tinoceras, made by our artist,
after much consideration and careful study of the valuable cast
exhibited in the Natural History Museum at South Kensington, which was
generously presented by Professor Marsh (Gallery I. Case MM on plan).
In planning this and other restorations, both artist and author have
received valuable assistance from Dr. Henry Woodward, F.R.S., Keeper
of the Geological Department of the Museum, who is ever ready to help
with his great knowledge those who come to consult him.
There may be differences of opinion among palæontologists as to the
appearance presented by this formidable creature when alive, and no
doubt the nature of the skin must always be more or less a matter of
conjecture in such cases, but we venture to hope that the restoration
here given, based as it is upon Mr. Smit's thorough acquaintance with
living animals and Professor Marsh's description, will meet with a
favourable verdict.
[Illustration: Fig. 42.--Skeleton of _Tinoceras ingens_. (After
Marsh.)]
Looking at the skeleton, one is struck with a certain resemblance to
the rhinoceros on one hand, and to the elephant on the other. The legs
are very elephantine, and the feet must have been covered with thick
pads, but the body reminds one more of the rhinoceros; and yet, again,
there is some suggestion of the hippopotamus. The eye was small and
deep set, as in the rhinoceros. In the upper jaw the two canine teeth
are developed into dagger-shaped tusks, the use of which can only be
conjectured. In the females these are but slightly developed.
[Illustration: Plate XIV.
A LARGE EXTINCT MAMMAL, TINOCERAS INGENS.
From North America. Length about 12 feet (without the tail).]
It is quite clear, then, that we cannot place the Dinoceras in any
order of living mammals. It is what palæontologists call a
"generalised type;" that is to say, it presents certain characters
seen in several groups of living quadrupeds, and not any of those
elaborated or highly developed parts which we see in such animals
to-day. Thus the proboscis of the elephant is a greatly elongated
nose; in other words, the elephant is highly "specialised" in that
direction, whereas our Dinoceras had no proboscis, or only a very
slight one.
[Illustration: Fig. 43.--Skull of _Dinoceras mirabile_. (After
Marsh.)]
Again, the six remarkable bony protuberances of the skull served to
some extent as horns, and probably were covered with thick bosses of
skin, and did not support true horns like those of our modern oxen and
other ruminants. Speaking of these protuberances, Professor Marsh
says, "None of the covering of these elevations, or horn-cores, has,
of course, been preserved; yet a fortunate discovery may perhaps
reveal their nature by the form of a natural cast, as the eye-ball of
the Oreodon is sometimes thus clearly indicated in the fine Miocene
matrix which envelops these animals." It looks rather as if we have
here an early stage in the evolution of horns, and it may be that in
the course of subsequent ages such prominences as those developed into
true "horn cores," such as sheep or goats have, while the thick bosses
of skin that covered them slowly developed into the true horns that
are attached to these cores. If this is so, then we have here another
instance of a "generalised" structure. Again, the limbs with their
five toes tell us at once that the creature's place in Nature is
outside of those two great groups of modern ungulates, or hoofed
quadrupeds, the odd-toed and the even-toed, represented on the one
hand by the horse, rhinoceros, and tapir, on the other by the pig,
camel, deer, ox, and many other forms. Probably the two groups had not
at this early period branched off from the primitive ungulate stock
with five toes in each foot, of which the elephant is a living
descendant, and from which also the Dinoceras must have come.
[Illustration: Fig. 44.--Cast of brain-cavity of _Dinoceras mirabile_.
(After Marsh.)]
The limbs were strong and massive, but the brain was remarkably small,
so that our Dinoceras cannot be credited with any high degree of
intelligence: and here again we see an absence of "specialisation"
compared with the sagacious elephant. Professor Marsh has taken casts
of its brain-cavity (see Fig. 44). These casts show that the brain was
smaller (in proportion to the size of the animal) than in any other
mammal, whether living or extinct--and even less than in some
reptiles! In fact, it was a decidedly reptilian kind of brain.
Perhaps it may seem hardly credible, but so small was the brain of
Dinoceras mirabile, that it could have been pulled through the
apertures (neural canals) of all the neck vertebræ! In certain
marsupials of the present day we find an approach to this kind of
brain. It seems to be an established fact, according to Professor
Marsh, that all the Eocene or earlier Tertiary mammals had small
brains. His researches among fossil mammals have led him to the
important conclusion that, as time went on, the brains of mammals grew
larger; and thus he has been able to establish his law of brain-growth
during the Tertiary period, a law which appears to be plainly recorded
in the fossil skulls of succeeding races of ancient mammals. The
importance of a discovery such as this cannot fail to strike the
imagination of even the most unlearned in geology as being singularly
suggestive and instructive. It is not difficult to picture these dull,
heavy, slow-moving creatures haunting the forests and palm jungles
around the margin of the great Eocene lake, into the waters of which
their carcases from time to time found their way--perhaps swept down
by floods. No footprints have been discovered as yet.
The Dinocerata were very abundant for a long time during the middle of
the Eocene period. The position of their remains suggests that they
lived together in herds, as cattle do now, and they probably found an
abundance of food in the shape of succulent vegetation round the great
lake. Geological evidence points to their sudden extinction before the
close of the Eocene period; but it is difficult to understand this.
Professor Marsh thinks that from their sluggish nature they were
incapable of adapting themselves with sufficient rapidity and
readiness to new conditions, such as may have been brought about by
geographical changes. It must be admitted, however, that the
geological record in this region does not give evidence of any sudden
change. Possibly they may only have migrated to some other region,
where their remains have not yet been discovered, or where, for
various reasons, their skeletons were not preserved. In this Eocene
lake, where sediments went on being quietly deposited for a long time,
we have the most favourable conditions for the preservation of the
different forms of life that flourished round its borders.
In the museum at Yale College are collected the spoils of numerous
expeditions to the West, and the many tons of bones lying there are
believed to represent the remains of no less than two hundred
individuals of the Dinocerata. So perfectly have these bones been
preserved by Nature that, even if the creatures had been living now,
the material for studying their skeletons could hardly be more
complete. Professor Marsh recognises three distinct types in this
strange group of quadrupeds, on each of which a genus has been
founded. The first and oldest form is the Uintatherium, which takes
its name from the Uinta Mountains. This, as might be expected, is the
most primitive or least specialised form, and comes from lower strata.
The most highly developed or specialised form is the Tinoceras, and
this is found at the highest geological level or "horizon."
Between these two extremes, and from an intermediate horizon, comes
the Dinoceras,[41] so that in tracing these animals through the strata
in which they occur the geologist finds that he is following for a
while the course of their evolution. Doubtless there were many slight
differences presented by the members of this group, but at present it
has not been found possible to determine the number of species,
although about thirty forms more or less distinct have been
recognised. Professor Marsh says that the specimen of the skull of
Dinoceras mirabile, on which the whole order Dinocerata was founded,
is, fortunately, in a very perfect state of preservation, and that it
belonged to a fully adult animal. Moreover, it was embedded in so soft
a matrix that the brain-cavity and the openings leading from it could
be worked out without difficulty. In removing the skull from the rock,
on the high and almost inaccessible cliff where it was found, two or
three important fragments were lost; but Professor Marsh, after a
laborious search, recovered them from the bottom of a deep ravine,
where they had been washed down and covered up.
[41] The Dinoceras of Marsh is the same form as Eobasileus of Cope.
Uintatherium was discovered by Leidy.
It is about twenty-two years since the wonderful forms of life sealed
up within these Eocene lake-deposits first became known to science.
Long before then, however, the wandering Indian had been accustomed to
seeing strange-looking skulls and skeletons that peeped out upon him
from the sides of cañons and hills, as the rocks that enclosed them
crumbled away under the influence of atmospheric agents of change--the
ceaseless working of wind, rain, heat, and cold. To his untrained mind
no other explanation suggested itself than the idea that these were
the bones of his ancestors, which it would be highly impious to
disturb. _Requiescant in pace!_ So he left them in peace. Perhaps he
believed in a former race of human giants; if so, these would be their
bones. Long before Professor Marsh's expeditions, the earliest
squatters, trappers, and others used to bring back news of marvellous
monsters grinning from the ledges of rock beneath which they camped.
At last these tales attracted the notice of some enthusiastic
naturalists in the eastern States. Professor Leidy obtained a number
of bones, from which he was able to bring to light an extinct creature
at that time unknown to science, namely, the Uintatherium. Professor
Cope also described some extinct animals disinterred by himself from
the same region.
But our knowledge of the Dinocerata is chiefly due to Professor Marsh,
who has despatched one expedition after another, and who, after many
years of laborious research both in the western deserts and in his
wonderful collection at Yale College, has published a splendid
monograph on the subject. No trouble and no expense have been spared
in order to obtain material for this great work, and all geologists
must feel grateful to Professor Marsh for so liberally devoting his
time and his private resources in order to advance the science of
Palæontology.
The region in which the remains occur of the remarkable group of
extinct animals now under consideration, has a peculiar scenery of its
own, unlike anything in Europe. The following graphic description of
its features is from the pen of Sir Archibald Geikie:--[42]
[42] _Nature_, vol. xxxii. p. 97.
"On the high plateau that lies to the west of the Rocky Mountains,
along the southern borders of the Wyoming territory, the traveller
moving westwards begins to enter on peculiar scenery. Bare, treeless
wastes of naked stone, rising here and there into terraced ledges and
strange tower-like prominences, or sinking into hollows where the
water gathers in salt or bitter pools. Under the cloudless sky, and in
the clear dry atmosphere, the extraordinary colouring of these
landscapes forms, perhaps, their weirdest feature. Bars of deep red
alternate with strips of orange, now deepening into sombre browns, now
blazing out again into vermilion, with belts of lilac, buff, pale
green, and white. And everywhere the colours run in almost horizontal
bands, running across hollows and river-gorges for mile after mile
through this rocky desert. The parallel strips of colour mark the
strata that cover all this wide plateau country. They are the tints
characteristic of an enormous accumulation of sedimentary rocks, that
mark the site of a vast Eocene lake, or succession of lakes, on what
is now nearly the crest of the continent."
In this strange region the flat-topped hills, table-lands, or
terraces, as they are variously named, seen from lower levels, are
usually called "buttes," especially when they are of limited extent.
This name is of French origin, and signifies a bank of earth or
rising ground. It is also applied in a limited sense to the more
prominent irregularities of the deeply sculptured slopes of the larger
terraces. These buttes, therefore, vary in extent, from a mere mound
rising slightly above the level of the plains to hills of varied
configuration reaching to the level of the broader buttes or terraces.
The _débris_ resulting from the continual wearing away, or demolition
of these buttes and terraces, now lies spread out on the plains below.
From the lower plains the smaller terraces appear like vast earth-work
fortifications, and when not too much cut up by erosion, remind one of
long railway embankments. But in many cases the terraces are so much
cut up by narrow ravines that they appear as great groups of naked
buttes rising from the midst of the plain. Nothing can be more
desolate in appearance than some of these vast assemblages of
crumbling buttes, destitute of vegetation, and traversed by ravines,
in which the watercourses in midsummer are almost all dried up. To
these assemblages of naked buttes, often worn into castellated and
fantastic forms, and extending through miles and miles of territory,
the early Canadian _voyageurs_ gave the name _Mauvais Terres_. They
occur in many localities of the Tertiary formations west of the
Mississippi River. Professor Leidy, who with two friends made an
expedition in search of fossils to Dry Creek Cañon in this region of
the "Bad Lands," about forty miles to the southeast of Fort Bridger
(Wyoming), thus describes his impressions:--
"On descending the butte to the east of our camp, I found before me
another valley, a treeless barren plain, probably ten miles in width.
From the far side of this valley butte after butte arose and grouped
themselves along the horizon, and looked together in the distance like
the huge fortified city of a giant race, the utter desolation of the
scene, the dried-up watercourses, the absence of any moving object,
the profound silence which prevailed, produced a feeling that was
positively oppressive. When I thought of the buttes beneath our feet,
with their entombed remains of multitudes of animals for ever
extinct, and reflected upon the time when the country teemed with
life, I truly felt that I was standing on the wreck of a former
world."
These old lake-basins, in which so many forms of life have been sealed
up, all lie between the Rocky Mountains on the east, and the Wasatch
Range on the west, or along the high central plateau of the continent.
As the mountains were slowly elevated, part of the old sea of the
Cretaceous period (that sea in which the "sea-serpents" played so
important a part) was enclosed and cut off from the ocean. Rivers
began to pour their waters into it, so that the waters became less and
less salt, until at last a fresh-water lake, or series of lakes, was
formed. As the upward movement of this region continued these lakes
were all the while receiving sedimentary materials, such as sand and
mud, from the rivers, until finally they were filled up, but not until
the sediments had formed a mass of strata over a mile in thickness.
Thus we see how favourable were the conditions for a faithful record
of Eocene life-history.
But another process was going on which helped to bring them to an end;
for they were being slowly drained by the rivers that flowed out of
them, and these rivers kept on continually deepening their channels,
so that we have dry land where the lakes once were. _Now_ the region
is over 6000 feet above the sea, and probably more than one-half of
these fresh-water deposits have been washed away, mainly through the
Colorado River. What is left of the Eocene strata forms the "Bad
Lands." The same geological action that has cut up and carved out this
region into buttes, cañons, cliffs, peaks, and columns of fantastic
shapes, has also brought to light the extinct animals preserved in the
rocks, much in the same way as an old burial-ground, if cut up by
intersecting trenches, might be made to yield up the bones of those
who for generations had been buried therein.
Professor Marsh first discovered remains of Dinocerata in 1870, while
investigating this Eocene lake-basin, which had never before been
explored. It was here, also, that he found the wonderful series of
fossil horses by means of which he has been able to prove that our
modern horse is descended from a small quadruped with five toes, and
to show the different stages in its evolution. Here, also, were found
old-fashioned types of carnivorous quadrupeds, of rodents, and of
insectivorous creatures. But reptiles as well as quadrupeds flourished
on the borders of the old lake, for the remains were found of
crocodiles, tortoises, lizards, and serpents; its waters, too, were
well stocked with fish.
Everything here testifies to a long continuance of those conditions
under which plant and animal life can flourish, namely, a warm
climate, plenty of food, and freedom from those physical changes
which, by altering the geographical features of a country, bring so
many important consequences in their train. The geological record
tells us that this happy state of things lasted all through the Eocene
period, and until the fresh-water lakes had at last been drained away
by their outflowing rivers.
In October, 1870, a later Eocene lake-basin was discovered by the same
exploring party, and this Professor Marsh calls the Uinta basin,
because it was situated south of the Uinta Mountains. "In the attempt
to explore it," he says, "our party endured much hardship, and also
were exposed to serious danger, since we had only a small escort of
United States soldiers, and the region visited was one of the
favourite resorts of the Uinta-Utes. These Indians were then, many of
them, insolent and aggressive, and since have been openly hostile, at
one time massacring a large body of Government troops sent against
them. Two subsequent attempts ... to explore this region met with
little success."
This lower lake was of later (or upper) Eocene age, and the extinct
animals preserved in its ancient bed appear to resemble more nearly
those of the famous Paris basin, referred to in the beginning of this
chapter, than any yet discovered in America. But the basin north of
the Uinta Mountains, where alone the Dinocerata had been found,
offered so inviting a field that, in the spring of 1871, Professor
Marsh began to explore it systematically. He organised an expedition,
with an escort of U.S. soldiers, and the work continued during the
whole season. In this way a large collection was secured. Explorations
were continued in the spring of the following year, which resulted in
the discovery of the type specimen of the Dinoceras mirabile. Another
expedition was organised in 1873, also with an escort of soldiers, and
a great many specimens were collected. These researches were continued
during 1874, and again in 1875, with good results. Since then various
small parties have been equipped and sent out by Professor Marsh to
collect in the same region of the "Bad Lands;" and, finally, during
the entire season of 1882, the work was vigorously prosecuted under
his direction, and afterwards under the auspices of the United States
Geological Survey. This brief account of the difficulties and
hardships encountered by Professor Marsh and his companions, for which
we are indebted to his exhaustive monograph, will serve to give some
idea of the nature of those labours, undertaken in the cause of
Science, which he has brought to so successful an issue.
* * * * *
In the country east of the Rocky Mountains, including the states of
Dakota, Nebraska, Wyoming, and part of Colorado, Professor Marsh has
discovered the remains of yet another strange group of large
quadrupeds. The best known of these is Brontops, of which the skeleton
is seen in Fig. 45. These animals lived after the Dinocerata, namely,
in the Miocene period, and were the largest American mammals of that
period. They constitute a distinct family more nearly allied to the
rhinoceros than to any other living form. The skeleton on which Fig.
45 is founded was the most complete of any yet discovered by Professor
Marsh. Portions of it were exhumed at different times, but it was
first found in 1874. Our artist has made the restoration seen in Plate
XV. from this skeleton, as figured by Professor Marsh.
[Illustration: Plate XV.
A HUGE EXTINCT MAMMAL FROM NORTH AMERICA. BRONTOPS ROBUSTUS.]
This strange group of creatures flourished in great numbers on the
borders of an old lake of Miocene age. The Brontops was a heavy
massive animal, larger than any of the Dinocerata, with a length of
twelve feet, not including the tail, and a height of eight feet. The
limbs are shorter than those of the elephant, which it nearly equalled
in size. As in the tapir, there were four toes to the front limbs, and
three to the hind limbs. Its skull was of a peculiar shape, shallow,
and very large. That of Brontops ingens is thirty-six inches long, and
twenty inches between the tips of the two horns, or protuberances. The
creature was probably provided with an elongated, flexible nose, like
that of the tapir, but not longer, because the length of the neck
shows that it could reach the ground without the aid of a trunk such
as the elephant's. It is doubtful if the two prominences on the front
of the skull were provided with horns, for, if directed forwards, they
would interfere with the animal when grazing.
[Illustration: Fig. 45.--Skeleton of Brontops robustus. (After
Marsh.)]