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The figure presents an outline of the animal as it may have appeared when engaged in obtaining food from the trees of the forests it inhabited. The attitude is the same as that in which the perfect skeleton in the Royal College of Surgeons is set up. Fig. 146
The Megalonyx* is another genus, chiefly known
by bones of the extremities. It appears to have had the thumb more developed, and greater freedom of motion of the fore extremity. In other respects, and in its proportions, it probably resembled the Mylodon. The Scelidotherium + differs rather more from the
* Mɛyan (megale), great; ovv (onyx), a claw.
+ΣKελi, gen. σkeλidog (scelidos), the thigh; Onpiov (therion), beast.
megatheroid type than either the Mylodon or Megalonyx, and even exceeds them in some of those monstrous proportions for which they are so remarkable. It is also interesting as exhibiting a transition to the ant-eater and armadillo, which it resembles more than the sloth in the form and structure of the skull. In all important points, however, as well with regard to the head as the vertebral column, and also in the dentition, the scelidothere and the Megatherium are so closely analogous that they hardly admit of a separate description. In the fore extremities the same singular contrivances present themselves; and in the hinder extremities and the tail, the strength is perhaps greater in proportion than in any known animal, living or extinct.
Of these bones the femur, or thigh-bone, is the most remarkable, and it differs in some points from the corresponding part of the megathere, its breadth being greater in proportion to its length than is the case even in that singularly proportioned animal. It appears, that, although the total length of the scelidothere could not have been greater than that of a Newfoundland dog, the fore extremities not being larger, and the height not nearly so great, the hind extremities were more gigantic than those of the largest rhinoceros or hippopotamus, and the animal was provided with a tail so thick and strong, that there is nothing in existing nature with which to compare it.
We have now only to consider what can have been the habits of animals so strangely organized, resembling the sloth in the structure of the teeth and other characters which mark the food to have been the leaves and tender twigs of trees, but rather approximating to
the armadilloes and ant-eaters in certain peculiar contrivances for strength which in these living edentates are connected with habits of digging and burrowing beneath the surface of the earth. All the extinct species we have yet discovered of the group attained dimensions which seem to have unfitted them entirely for any such habit, neither allowing them to climb trees like the sloth, or to burrow like the mole, the ant-eater, or the armadillo.
We know that the general proportions of the megatheroid animals resemble those of the elephant ; but, although their body was relatively quite as large, their legs were shorter and much thicker, and their fore extremities were endowed with greater facilities of motion.
The head, moreover, is very diminutive, and the neck, although longer, was not so much so as to enable the animal to reach to any height above its body. It is also quite certain that these animals could not have had a long proboscis, and some had no proboscis at all; so that the question presents itself, how they could have obtained the leaves of trees, which the structure of their teeth shows to have been the only food adapted for them.
Now we have seen, in the course of our investigation concerning the peculiarities of structure of these animals, that they exhibit in all cases very remarkable modifications of the extremities, the hinder part of the body being enormously large, powerful, and massive, and bearing every mark of the greatest possible adaptation for resisting pressure, forming as it were a point d'appui, from which the rest of the body could act with safety and certainty. It is also
the case that the fore extremities were exceedingly powerful, but in a different way, admitting of free motion, and provided with large and prominent claws, so that they were well adapted for grasping the trunk or the larger branches of a tree, while the forces concentrated upon them from the broad posterior basis are such as could well assist in the act of wrenching off a branch, or even, if need were, uprooting a tree.
There is, indeed, no other reasonable conclusion to be drawn from the consideration of the framework of these gigantic quadrupeds. Their massive proportions cannot but arrest the attention of even the most indifferent beholder, and such proportions seem to imply powers and actions as peculiar to the living animal, as are these modifications to the framework of the body handed down to us.
The enormous pelvis of the Megatherium proclaims itself the centre, whence muscular masses of unwonted force diverged to act upon the trunk, the tail, and the hind legs; but, in order that it should possess stability and resistance equivalent to the due effect of the forces acting from it, it required to be bound down and supported by members of corresponding strength.
We find, accordingly, a thigh-bone, which, though longer than the shoulder-bone, is half as broad as it is long, and is provided with bony crests, giving unequivocal evidence of the magnitude and power of the muscles once attached to and working from them.
This thigh-bone, placed vertically, rested on leg bones of corresponding magnitude, and on a foot which in all its proportions must have served as a fit basis for the leg. The foot was of great length
(equalling, if not surpassing, that of the femur); the prolongation of the heel served as a fulcrum, and the powerful claw of the middle toe held fast to the ground, at the moment when the forces of the forelimbs were exerted. There was also a strong and powerful tail, its proportions being exactly such as to complete with the two hind legs a tripod strong enough to afford a firm foundation for the massive pelvis, and sufficient resistance to the forces acting from that great bony centre. The proportions of these parts, colossal as they are, lose their anomalous character when we view them as the fixed point towards which the fore part of the body was to be drawn when the animal was in the act of uprending a tree to serve as its subsistence; and the value of all these contrivances is seen, when we understand the habits of these singular animals.
The nature of the food required by them has been already mentioned; and since it is utterly incredible, that creatures so vast in their proportions should have been either climbers of trees or burrowers in the earth, while their teeth and jaws were expressly adapted for the comminution of foliage, and their height and general form prevented them from reaching up to obtain such food, it only remains for us to conclude that they were enabled by their great strength to uproot the trees themselves, and bring the foliage on which they fed within the reach of their mouths or short trunks. Having thus obtained the means of supporting life, and being provided with a tongue of remarkably large size and strength, not less adapted than that of the giraffe (and apparently even larger and stronger in proportion), the creature