The rhinoceros-sized "Promegatherium" of the Miocene is suggested to be the ancestor of "Megatherium". The oldest (and smallest) species of "Megatherium" is "M. altiplanicum" of Pliocene Bolivia. It was very similar to "Promegatherium", and was also about the size of a rhinoceros. "M. tarijense" has been regarded as a medium-sized "Megatherium" species, larger than "M. altiplanicum", but smaller than "M. americanum". It roamed from the Tarija Basin in Bolivia to Yantac in Peru. Species of "Megatherium" became larger over time, with the largest species, "M. americanum" of the Late Pleistocene, reaching the size of an African elephant. The oldest records of "M. americanum" are from the latter half of the Middle Pleistocene, around 0.4 Ma.