The notoungulates—literally "southern hoofed animals"—were the largest order of South American ungulates. There are about 100 genera grouped into 4 suborders. The suborders may already have diverged by the time South America was detached from North America at the end of the Paleocene.
The isolation of South America allowed the separate evolution of its mammal groups, many of which diversified into ecological niches taken, elsewhere in the world, by other groups.
Many notoungulates were small animals which looked and lived much like rabbits or beavers. Other, larger species came to resemble sheep, wart-hogs, horses, rhinoceroses and hippopotamuses. That they were related is confirmed both by the arrangement of cusps on the teeth and by ear bones, which are unique to the order.
Although most specimens are of South American origin, a few are also known from late Paleocene and Early Eocene deposits in North America. The latter groups quickly died out, and from then onward the order existed only in South America.
The notoungulates achieved their greatest success as a group in the Oligocene, but they were still abundant early in the Miocene. Thereafter they declined. They have no surviving members. The last notoungulates became extinct in South America in the Pleistocene, about 1 million years ago, shortly after the emergence of the Panamanian isthmus opened the way to the invasion of mammal groups from the north.
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