LATE PLIOCENE to PLEISTOCENE PERIOD: 1.8 million years ago
Giant ground sloths were slow-moving herbivores that died out at the end of the Pleistocene Period. They are survived today only by dog-sized tree-dwelling forms found in Central and South America. Some prehistoric giant ground sloths grew as large as a modern elephant. Giant ground sloths were so large that they were not able to climb trees, hence their land-roving lifestyle. Giant sloths are related to armadillos, sharing similar designs in their blunt, deep skulls as well as their mandibles. Their jaws were powered by very robust muscles for chewing vegetation and each jaw possessed three to five teeth. Giant ground sloths possessed very large feet sporting massive claws. Their claws were so large that they walked on the sides of their feet. Sloths could stand on their hind legs aided by a very strong tail, to reach vegetation at levels higher than other herbivores could typically reach.
It is theorized that sloths first entered North America through Florida, nine million years ago from the South American continent. The first sloths in North America were the Mylodonts represented by two species of the genus Thinobadistes and the Megalonychids represented by the genus Pliometanastes. Later in the Pliocene, sloths again entered North America with two Mylodont species, Glossotherium chapadmalense and Paramylodon harlani, andwith the Megalonychids genus, Megalonyx. By the Early Pleistocene, the largest ground sloths appeared, the Megatheriidae with several species represented. The largest ground sloth to have ever lived in North America is a member of this last group and is known as Eremotherium. The male Eremotheriums grew to an estimated THREE TONS. Giant ground sloths in the Americas went extinct at the end of the Pleistocene.