GEOGRAPHICAL DISTRIBUTION OF ANIMALS
gonia had no animal that can be regarded as an ancestor of any of those that are put in the second category—animals like those of North America and the Old World. All the mammals of that time and region were either such as gave rise to the peculiar South American forms of the Pleistocene and Recent epochs or such as died out without leaving any descendants. There was a great assemblage of hoofed animals, but they were peculiar, unknown from any other part of the world, and all are extinct and left no descendants in the modern world. There were predaceous creatures, beasts of prey, but no members of the order Carnivora, for these ancient flesheaters of Miocene Patagonia were marsupials, very like the so-called Tasmanian wolf (Thylacynus) and related to the opossums. Of the modern cats, wolves, skunks, and other northern carnivorous animals there was no trace; nor of the tapirs, peccaries, llamas, or deer of to-day. There were rodents in great variety, but they were all of the peculiar South American kinds; of the northern rats, mice, squirrels, and rabbits there was not a single representative.
In contemporaneous (middle Tertiary) North America there was an equally rich and varied mammalian fauna, but one totally different from that of the southern continent and very like that of the Old World. In addition to certain characteristically North American groups, not yet known from any other region, there were ancestral types of elephants, rhinoceroses, horses, tapirs, peccaries, deer, antelopes, camels, cats, sabre-tooth tigers, wolves, weasels, raccoons, rats and mice, squirrels, marmots, beavers, hares, and rabbits. The assemblage is essentially that of the Old World, though it shows certain local differences, and it is completely unlike that of South America.
About in the middle or perhaps in the later part of the
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