meg·a·the·ri·um 
(mĕg′ə-thîrē-əm)
(mĕg′ə-thîrē-əm)n.
A large extinct ground sloth of the genus Megatherium of the Miocene Epoch through the Pleistocene Epoch.
[New Latin Megathērium, genus name : MEGA- + Greek thērion, wild beast; see TREACLE.]