Megatherium skeleton, 19th-century artwork. This large, extinct ground sloth lived from the Miocene through the Pleistocene epochs from 2 million years ago to 10,000 years ago. It was primarily found in South America. A herbivorous mammal with long curved claws, it was as large as an elephant (up to 6 metres long) and among the largest land mammals of its time. Megatherium fossils were among those discovered by Charles Darwin in South America in his 1830s voyage on HMS Beagle. Artwork from 'London' (Charles Knight, 1841).