The peculiar productions of South America in the way of animals appear to be the members of the group of mammals called Edentata found nowhere else. When, however, South America, which once was an island, joined on to North America, numbers of animals, mastodons, horses, tigers, and tapirs, emigrated from north to south, and perhaps proved too much for the aboriginal or native beasts. At any rate, all the big South American mammals died out, and now there are left only the small tree sloths, the small armadillos, and the strange-looking ant-eaters. But in quite late geological deposits of South America we find the bones of gigantic armadillos and of gigantic ground sloths, which lasted on till the time when man appeared on the scene.
The Glyptodon, of which there were several different kinds, was an enormous armadillo as big as an ox. Like their small, puny, modern descendants, they carried on their backs a hard case of bones, something like the shell of a tortoise. The modern armadillo's shell, however, is jointed so that the little animal can roll itself up into a ball, and in this direction, therefore, the armadillo, though it has decreased so much in size, has advanced in adaptability.
The Megatherium was nearly as big as an elephant, and its skeleton, though so much larger, is very similar to those of the small sloths of present-day South America. Its teeth also are very much like theirs. But whereas the living sloths climb trees, as they have learnt to do, the Megatherium's method was more primitive though quite as effective. It stood on the ground and pulled the trees down in order to eat the young branches. The Mylodon, which lived at the same time, was not so big, and its habits were similar. It had a number of little bony pieces scattered in its skin in the region of the back, like the pieces forming the bony case of the ancient armadillos; but the pieces in this case were not closely fitted together.
It was supposed that the Mylodon, like all the peculiar gigantic animals of South America, had become extinct as long ago as the Mammoth (of which we shall say more presently) or of the woolly rhinoceros which used to haunt Fleet Street. All these extinct South American animals were distinguished by peculiarly shaped teeth, and had no teeth at all in front. They are called, therefore, Edentata, and their representatives to-day are much smaller.
But some years ago Dr. Nordenskjold, a Scandinavian traveller, while exploring in Patagonia, found a vast cavern called the Ultima Speranza cave, on the western coast. From this cavern the settlers who lived close by had removed an enormous piece of skin covered with greenish-brown hair, and studded on its inner side with little knobs of bone. The skin was dry but sound. When it was placed in water it gave out a smell which, though unpleasant, was very interesting, for it showed that the animal which had worn it could not have been dead thousands or even many hundreds of years. It was, in fact, evidently a piece of the skin of a Mylodon, which had survived in this region until modern times.
Further explorations were made in the cavern by Dr. Moreno, of La Plata, and other naturalists, and an immense quantity of bones was obtained, and more portions of the skin of Mylodon with the hair on. The cavern had been inhabited probably several centuries ago by Indians, for human bones and weapons were obtained.
The remains of as many as twenty Mylodons have been obtained from the cavern, and many of the bones are cut or broken in a way which leads us to suspect that the human inhabitants of the cave cut up the dead Mylodons for food, and split their bones to obtain the marrow!
Some of the Mylodon bones, skulls, jaw-bones, leg-bones, etc., are smeared with blood and have pieces of cartilage and tendon attached. There are other evidences which go to show that the Indians may have kept the Mylodons alive in the cave and fed them with hay brought from the outside. Anybody who would care to see the last of the great extinct animals can inspect some of these remains at the museum in Cromwell Road, London.
Besides the relics of the Mylodon and of Man the cavern has yielded bones and teeth, and many horny hoofs belonging to a kind of extinct horses; and this constitutes one of the puzzling things about this cave treasure. The cave is in a part of the country very difficult to reach, and though Sir Thomas Holdich and Mr. Hesketh Prichard made efforts to reach it again and explore it systematically and scientifically, there is a great deal about it that seems likely to remain unexplained.
The bones that were found are not buried in lime or any preserving stone; but lie in sand where one would expect them to have perished long ago if they had been of any great age. Yet side by side with them are the bones of a long-extinct horse; and there is no tradition among the Indians to-day of any huge beast corresponding to the Mylodon. Sir E. Ray Lankester has pointed out that the whole of South America has been submerged and has risen (and is rising still) for many centuries. Possibly the rocks and high lands where the Mylodon cavern occurs formed an island during the submergence, where a number of early animals took refuge and survived until the re-elevation of the land—and so lived on in the present condition of the land surface until fifty or a hundred years ago. The great land tortoises (like the Galapagan[17] tortoise) have similarly survived on a few equatorial islands. Possibly, though it does not seem very likely, the Mylodon is still living in similar caverns in this region, as yet unvisited by man.