Megatherium (/mɛɡəˈθɪəriəm/ meg-ə-theer-ee-əm from the Greek mega [μέγας], meaning "great", and therion [θηρίον], "beast") was a genus of elephant-sized ground sloths endemic to South America that lived from the late Pliocene through the end of the Pleistocene. Its size was exceeded by only a few other land mammals, including mammoths and Paraceratherium.
Megatherium was one of the largest land mammals known, weighing up to 4 tonnes and measuring up to 6 m (20 ft) in length from head to tail. It is the largest known ground sloth, as big as modern elephants, and would have only been exceeded in its time by a few species of mammoth. The group is known primarily from its largest species, M. americanum. Megatherium species were members of the abundant Pleistocene megafauna, large mammals that lived during the Pleistocene epoch.
Megatherium had a robust skeleton with a large pelvic girdle and a broad muscular tail. Its large size enabled it to feed at heights unreachable by other contemporary herbivores. Rising on its powerful hind legs and using its tail to form a tripod, Megatheriumcould support its massive body weight while using the curved claws on its long forelegs to pull down branches with the choicest leaves. 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. Although it was primarily a quadruped, its trackways show that it was capable of bipedal locomotion. Biomechanical analysis also suggests it had adaptations to bipedalism.
Some experts believe that its jaw may have housed a long tongue, which it would use to pull leaves into its mouth, similar to the modern tree sloth. Others question this view. Some of the elements in Megatherium's oral cavity were fused together: a rigidly articulated stylohyal and epihyal, and the apparatus lies farther anteriorly, which together with the elongated, steeply inclinedmandibular symphysis, indicates a relatively shorter geniohyoid muscle and thus more limited capacity for tongue protrusion. It was well adapted for strong, predominantly orthal (up-down) movement for eating rough vegetation. Megatherium possessed the narrowest muzzle of all ground sloths from the Pleistocene. This leads paleobiologists to believe that it was a very selective eater. It had the ability to pick and choose which leaves and twigs it would consume. Megatherium had a large narrow prehensile lip that was capable of grabbing and tearing off particular leaves and twigs and other sorts of vegetation.