ARSINOITHERIUM

genus of extinct large, primitive, hoofed mammals that have been found as fossils in Egypt in deposits of the Oligocene Epoch (which occurred from 36.6 to 23.7 million years ago). The animal, probably a swamp dweller, reached a length of about 3.5 m (11 feet), and was about the size of a large rhinoceros. It carried an enormous pair of horns on the nasal bones and an additional, smaller pair of horns on the frontal bones.