UINTATHERIUM

extinct genus of large, primitive hoofed mammals found as fossils in North America in terrestrial deposits of the Middle and Late Eocene Epochs (52 million to 36.6 million years ago). The uintatherium, which was as large as the modern rhinoceros, was among the largest animals of its time. The limbs were strongly constructed in order to support the massive body. The skull was mostly occupied by bone rather than brain, and uintatherium must have had a very limited intelligence. Three pairs of bony growths, or protuberances, were present on the skull of the uintatherium. The anteriormost pair may have supported prominent horns. Uintatherium's teeth were distinctive: males of the genus possessed large, powerful canines; incisors were absent in the upper jaw but present in a reduced state in the lower; and the upper molars were characterized by the presence of V-shaped crests. By the end of the Eocene Epoch, uintatherium and closely related forms became extinct; they were unable to adapt to the changing environmental conditions of that time.