Megatherium americanum (Great Beast) was a genus of elephant-sized ground sloths native to America from the Pliocene through Pleistocene eras.. . Colour printed illustration by Heinrich Harder from "Tiere der Urwelt" Animals of the Prehistoric World, 1916, Hamburg. Heinrich Harder (1858-1935) was a German landscape artist and book illustrator. From a series of prehistoric creature cards published by the Reichardt Cocoa company. Natural historian Wilhelm Bolsche wrote the descriptive text.