Fig. 177.—Oreodon major. A generalised Miocene ruminant, with affinities to the Deer, Camel, and Hog. Greatly reduced.—After Leidy.
Fig. 178.—Lower Jaw of Megatherium. Greatly reduced. Post-Pliocene of South America.—After Owen.
Fig. 179.—Ungual Phalanx and Claw-core of Megatherium. Greatly reduced.
A very noteworthy and specially American group of mammals is that of the Edentates, the Sloths and Ant-eaters, a group which à priori we should have supposed would have been one of the earliest in time. They appear, however, first in the Miocene, without even any suggested ancestry, and are represented from the first by large species, though they attain their grandest stature in the Megatherium and Mylodon of the Post-Pliocene (Figs. 178, 179), which were sloths of so gigantic size that they must have pulled down trees to feed on their leaves, unless, indeed, there were trees equally colossal for them to climb. But before the modern time, like the American horses, the larger herbivorous forms suddenly disappear, and are now represented only by a few diminutive South American species, which can scarcely, by any stretch of imagination, be supposed to be descendants of their gigantic predecessors. The history of these animals, like those of the great Tertiary marsupials of Australia and the many Miocene elephants of India, affords a remarkable illustration of the persistence of similar groups of creatures in successive ages in the same region, along with diminution in magnitude and number of species toward the modern times.
