CHAPTER X.

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.

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.

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.

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.

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.

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.