Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: June 14, 2025
The process of elimination has at last led to this outline definition of a bison, but among the ungulates we have passed over, there are certain others which concern us because they are American.
From this summary review of the evolution of the Ungulates we must now pass to an even briefer account of the evolution of the Carnivores. The evidence is less abundant, but the characters of the Carnivores consist so obviously of adaptations to their habits and diet that we have little difficulty in imagining their evolution.
The feet have now only three or four toes; one or two of the side-toes have disappeared. This evolution, however, follows two distinct lines. In one group of these primitive Ungulates the main axis of the limb, or the stress of the weight, passes through the middle toe.
The earliest fossil remains of them were found in the latest Triassic strata lower jaws of small ungulates and marsupials. More numerous remains are found a little later in the Jurassic, and some in the Cretaceous. All the mammal remains that we have from this section belong to the lower promammals and marsupials; among these were most certainly the ancestors of the human race.
The elephant has developed along a separate and very distinctive line, as we shall see, and the hyrax is a primitive survivor of the ancestral group. Thus the evolutionist is able to trace a very natural order in the immense variety of our Ungulates. The hyrax has four toes on the front foot and three on the hind foot, and the feet are flat.
The Condylarthra seem to have gone out of existence before the time of the middle Eocene, but before this they had become separated into the two great divisions of odd-toed and even-toed ungulates, into which all truly hoofed beasts now living fall.
The rest of the Ungulates continued to develop through the Tertiary, and fortunately we are enabled to follow the development of two of the most interesting of them, the horse and the elephant, in considerable detail. As I said above, the primitive Ungulate soon branches into three types which dimly foreshadow the tapir, the horse, and the rhinoceros, the three forms of the Perissodactyl.
Again, it may perhaps be said that leaf-eating forms are exceptional, and that therefore the struggle to attain high branches would not affect many Ungulates. But surely, when these severe droughts necessary for the theory occur, the ground vegetation is supposed to be exhausted; and, indeed, the giraffe is quite capable of feeding from off the ground.
The phylogeny of the placenta has become more intelligible from the fact that we have found a number of transitional forms of it. The four great legions of the Placentals Rodents, Ungulates, Carnassia, and Primates are sharply separated to-day by important features of organisation.
The elephant itself, the last type of the Ungulates, has a clearer line of developments. A chance discovery of fossils in the Fayum district in Egypt led Dr.
Word Of The Day
Others Looking