Megatherium was a huge, bulky, slow-moving mammal that lived during the Pleistocene epoch in South America. It went extinct about 11,000 years ago. This ice-age mammal was the largest of the ground sloths; Megatherium's name means "great beast." Megatherium was named by paleontologist Richard Owen in 1856; the first Megatherium fossil was found in Brazil in 1789.