Megatherium (Great Beast) was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene epochs. Megatherium was one of the largest land mammals known, weighing up to eight tons, about as much as an African bull elephant. Although it was primarily a quadruped, its footprints show that it was capable of assuming a bipedal stance. When it stood on its hind legs it was about twenty feet tall, twice the height of an elephant. This sloth, like a modern anteater, walked on the sides of its feet because its claws prevented it from putting them flat on the ground. This animal appeared during Cenozoic era, the most recent era of geologic time, from about 65 million years ago to the present. The Cenozoic Era is characterized by the formation of modern continents and the diversification of mammals and plants. Grasses also evolved during the Cenozoic. The climate was warm and tropical toward the beginning of the era and cooled significantly in the second half, leading to several ice ages. Humans first appeared near the end of this era.