Megatherium cuvierii; Print; Megatherium was a genus of elephant-sized ground sloths endemic to South America; sometimes called the giant ground sloth; that lived from the Early Pliocene through the end of the Pleistocene.Only a few other land mammals equaled or exceeded Megatherium in size; such as large proboscideans (e.g.; elephants) and the giant rhinoceros Paraceratherium. Megatherium was first discovered in 1788 on the bank of the Luj醤 River in Argentina; the holotype specimen was then shipped to Spain the following year wherein it caught the attention of the esteemed paleontologist Georges Cuvier; Cuvier was the first to determine; by means of comparative anatomy; that Megatherium was a sloth.; skeleton