The carnivorous Megalosaurus (for its sharply serrated teeth indicate this mode of life) appears to have preceded the gigantic Iguanodon, whose dentition denotes a vegetable food. Like the giant sloths of South America—the Megatherium and the Mylodon—the Iguanodon was provided with a long prehensile tongue and fleshy lips to seize the leaves and branches on which it fed. Professor Owen estimates its probable length at between fifty and sixty feet, and to judge by the proportions of its extremities, and particularly of its huge feet, it must have exceeded the bulk of the elephant eightfold.
During the following Upper Cretaceous epoch flourished the Mosasaurus, a marine saurian, first discovered in the quarries of St. Peter’s Mount, near Maestricht,[[1]] and supposed to have been twenty-four feet in length. But the supremacy of the reptiles was now drawing to its close, and in the Tertiary period we at length see the Mammalia assume a prominent place on the scene of life. The oldest of these tertiary quadrupeds differ so widely from those of the present day as to form distinct genera. The Palæotheriums, for instance, of which there are seventeen species, varying in dimensions from the size of a rhinoceros to that of a hog, combine in their skeleton many of the characters of the tapir, the rhinoceros, and the horse, while the Anoplotheriums, whose size varied from that of a hare to that of a dwarf ass, resembled in some respects the rhinoceros and the horse, and in others the hippopotamus, the hog, and the camel.
In the Miocene epoch many of these more ancient quadrupeds no longer appear upon the scene, while others still flourish in its upper period along with still existing genera, and with forms long since extinct, such as the Dinotherium. This huge animal is particularly remarkable for its two large and heavy tusks, placed at the extremity of the lower jaw, and curved downwards like those in the upper jaw of the walrus. It was formerly supposed to be an herbivorous cretacean, and to have used its anterior limbs principally in the act of digging for roots. The remains on which these speculations were founded were the huge jaws and shoulder-blade discovered at Epplesheim in Hesse Darmstadt; but an immense pelvis of the animal, measuring six feet in breadth and four and a quarter feet in height, discovered by Father Sanno Solaro, in the department of the Haute Garonne, proves that this supposed aquatic pachyderm was a gigantic marsupial, and that the dependent trunks of the unwieldy animal, instead of serving the purpose of anchoring it to the banks of rivers, answered the more homely, but equally important office, of lifting the young into the maternal pouch. ‘The remarkable history of the successive discovery of its bones,’ says Professor Haughton, ‘and the change of views consequent thereupon, should teach geologists modesty in the expression of their opinion.’ During this period also flourished in India, along with many other strange forms of life, the Colossochelys Atlas, a tortoise of the most gigantic proportions, measuring, probably, nearly twenty feet on the curve of the carapace, and dwarfing into insignificance the great Indian tortoise of the present day.
The nearer we approach our own times, the greater becomes the proportion of still existing genera and species; and it is remarkable that as early as the Pliocene epoch we find a geographical distribution of mammalian life analogous to that which now characterises the various regions of the earth.
Thus the fossil monkeys of South America have the nostrils wide apart like all the existing simiæ of the new world, and fossil monkeys with approximated nostrils, the characteristic mark of all the old world quadrumana, are exclusively found in Asia and in Europe, where now a small species of monkey is confined to the Rock of Gibraltar, but where, in the Upper Miocene times, large long-armed apes, equalling man in stature, lived in the oak forests of France. Thus also South America, where alone sloths and armadilloes exist at the present day, is the only part of the world where, in the younger tertiary rocks, the remains of analogous mammals—the Megatherium, the Mylodon, and the Glyptodon—have been found.
The Mylodon was a colossal sloth, eleven feet long and with a corresponding girth. When we consider the huge size of the pelvis and the massiveness of the limbs, we must needs conclude that Professor Owen could not possibly have given the unwieldy animal a more appropriate surname than that of robustus.
The Megatherium was of still larger size. Its length was as much as eighteen feet, the breadth of its pelvis was six feet, and the tail, where it was attached to the body, must have measured six feet in circumference. The thigh bone was nearly three times as great as that of the largest known elephant, the bones of the instep and those of the foot being also of corresponding size. The general proportions both of the Megatherium and Mylodon resembled those of the elephant, the body being relatively as large, the legs shorter and thicker, and the neck very little longer. The Megatherium may have had a short proboscis, but the Mylodon exhibits no mark of such contrivance.
It is evident, from the bulk and construction of these huge animals, that they did not, like the sloths of the present day, crawl along the under side of the boughs till they had reached a commodious feeding place, but that, firmly seated on the strong tripod of their two hind legs and powerful tail, they uprooted trees or wrenched off branches with their fore limbs, which were well adapted for grasping the trunk or larger branches of a tree. The long and powerful claws were also, no doubt, useful in the preliminary process of scratching away the soil from the roots of the trees to be prostrated. This task accomplished, the long and curved fore claws would next be applied to the opposite sides of the loosened trunk. ‘The tree being thus partly undermined and firmly grappled with, the muscles of the trunk, the pelvis, and hind limbs, animated by the nervous influence of the unusually large spinal cord, would combine their forces with those of the anterior members in the efforts at prostration. If now we picture to ourselves the massive frame of the Megatherium, convulsed with the mighty wrestling, every vibrating fibre reacting upon its bony attachment with a force which the sharp and strong crests and apophyses loudly bespeak, we may suppose that that tree must have been strong indeed which, rocked to and fro, to right and left, in such an embrace, could long withstand the efforts of its ponderous assailant.’
GLYPTODON CLAVIPES.