Scelidotherium is a genus which is a trifle smaller than the last. It has only four properly-developed toes in the fore-foot, the thumb being rudimentary; of these, the first two bear claws. The hind-feet are also four-toed. Like Mylodon, Scelidotherium is a Pleistocene genus.
Glossotherium has a skull very much like the last two genera; but it is remarkable for the fact that the nostrils instead of being unprotected with bone anteriorly are there closed by a plate of bone formed by the well-developed premaxillae, the nostrils appearing at the sides, and giving the skull a curious likeness to that of a Chelonian. From a series of recent and most important observations it appears to be clear that this genus has survived into quite modern times.[[108]]
The well-known naturalist of La Plata, Señor Moreno, engaged in studies connected with the political boundary line between Chili and the Argentine, had occasion to visit Consuelo Cove on Last Hope Inlet in Patagonia. Hanging from a tree he noticed a piece of dried skin, which at once struck him as looking more like the remains of a Mylodon than of any living animal. The inhabitants regarded this piece of skin as a great curiosity, but were of opinion that it was the hide of a cow encrusted with pebbles! This fragment from a bygone age was originally described by Professor Ameghino, who had apparently seen some of the bonelets imbedded in it, as Neomylodon listai, "a living representative of the ancient Gravigrade Edentates of Argentina." That this piece of skin is of quite recent date seems to be proved by a number of considerations. In the first place it is covered by long hair of a light yellowish-brown colour; it does not seem likely that hair would preserve its character for geological epochs. The nearest corresponding case is that of the remains of Moas in New Zealand, whose feathers, dried skin, and tendons are known. Now the Moa was unquestionably contemporaneous with man, as abundant surviving legends prove, and indeed it cannot have been long extinct. Still, hair is a resisting structure, and in a dry cave, with no possibility of irruptions of floods, might retain its characters for long periods. The evidence, however, of more recent date is stronger than this. The skin shows patches of reddish colour, suggestive of course of blood-stains. A small piece of the outside of the skin at the cut edge, which presented the appearance of freshly or comparatively freshly dried fluid, was submitted to a chemical examination and shown to be serum! Dr. Lönnberg examined chemically a bit of the skin itself and found in it, after boiling, glue, "which proves that the collagen and gelatinous substances are perfectly preserved." After this it seems impossible to suppose that the skin can be of any very great age; for bacteria would have finished their work upon the serum and gelatine long ago. Combined with the fresh appearance of the skin is the very fresh appearance of the skull. In fact it is impossible to believe that the animal was not alive quite a few years since, relatively speaking. It is admitted that this animal was contemporaneous with man. There are actually legends of a creature which may have been this Glossotherium. "Ancient chroniclers inform us that the indigenous inhabitants recorded the existence of a
strange, huge, ugly monster, which had its abode in the Cordillera to the south of latitude 37. The Tehuelches and the Gennakens have mentioned similar animals to me, of whose existence their ancestors had transmitted the remembrance; and in the neighbourhood of Rio Negro, the aged Cacique Sinchel, in 1875, pointed out to me a cave, the supposed lair of one of these monsters, called 'Ellengassen'; but I must add that none of the many Indians with whom I have conversed in Patagonia have ever referred to the actual existence of animals to which we can attribute the skin in question."
A rude painting in a cavern, in red ochre, seems to Dr. Moreno (whose words we have just quoted) to be somewhat suggestive of a Glyptodon. There are some reasons for believing that this quadruped was kept by man as a domestic creature. In the cave are two walls of rough pieces of stone which seem to have dropped down owing to the wearing away of the roof; they also seem to have been loosely piled together to form two walls, within which enclosure an imperfect skull of the animal was found. This skull shows clearly that the so-called "Neomylodon" must be referred to Glossotherium or Grypotherium, as it is sometimes termed. This skull is perforated on the roof in such a way as could only have been effected (in the opinion of experts) by a weapon in the hand of a man. A hole in the skin has been even compared to a bullet-wound. But this it is perhaps unnecessary to discuss. The skin of Glossotherium is, like that of other extinct "Ground-sloths" (e.g. Mylodon), filled with small and irregular ossicles. But in Mylodon, the sculptured appearance of the dermal ossicles appears to indicate that they reached the surface of the body and were covered by epidermis alone, which is not the case with the animal now under consideration. The microscopic characters of the ossicles, too, show differences in the two. Glossotherium being "precisely intermediate between Mylodon and the existing Armadillo (Dasypus)." Now Glossotherium and Mylodon are regarded as forms which lie between the existing Anteaters and the Sloths of the same part of the world. We have already pointed out the facts of structure which lead to this conclusion. It might therefore be reasonably surmised that the hair of Glossotherium would be also intermediate, or at least like that of one of the two genera Myrmecophaga and Bradypus. But microscopical investigation has
negatived this supposition. It has shown that the Armadillos are in this matter the nearest relatives of Glossotherium. This result is important as tending further to confirm the close interrelationship of all the American Edentates as contrasted with the Old-World forms—a matter which has already been emphasised. It is suggested, however, that the absence of under fur, which is so well developed in the Sloth, and the difference shown in transverse sections from the hair of Myrmecophaga, may be explained by difference in habitat. Glossotherium lived under conditions similar to those under which the Armadillos live to-day. Thus the outer covering of the body became alike in the two cases, the same needs supervening in both genera.
Lestodon is another allied genus, which seems to possess canines. At any rate, in front of the four molars, and separated from them by a diastema, is a smallish, somewhat canine-like tooth, in both jaws.
Megalonyx and its allies are sometimes placed in a distinct family, Megalonychidae. Megalonyx itself had a skull very like that of Bradypus, being shorter and not so elongated as in the Mylodontidae. There is a strong tusk anteriorly, which is separated by a considerable space from the three molars lying behind it. Both pairs of limbs seem to have possessed five toes. This is a North American genus. It differs from the bulk of the American Edentates in having a complete jugal arch.
Megatherium is the type of yet a third family, Megatheriidae, of the Gravigrade Edentates. This creature is familiar from the many restorations which have been built up, and from its huge bulk, little short of that of an elephant. The skull, which is small for the size of the creature, has a complete jugal arch, from the middle of which depends a downward process as in other allied forms. The teeth grow to an extraordinary depth, and there are five of them in the upper and four in the lower jaw—on each side of course. The fore-limbs of the Megatherium are very much more slender than the enormously bulky hind-limbs, upon which and the equally massive tail the animal seems to have supported itself while tearing down branches of trees, upon whose leaves it fed. In the scapula the acromion joins the coracoid as in Bradypus; the clavicle is large. The fore-limb is four-toed, and the hind-limb three-toed. The latter has but one clawed digit (the third, i.e. the inner).