BRONTOTHERE

member of an extinct genus (Brontotherium) of large, hoofed, herbivorous mammals found as fossils in North American deposits of the Oligocene Epoch (36.6 to 23.7 million years ago). Brontotherium is representative of the titanotheres, large perissodactyls that share a common ancestry with the horse; indeed, the titanotheres probably were derived from a form that was very similar to the dawn horse (Hyracotherium). A brontothere stood at least 2.5 m (about 8 feet) high at the shoulder. Although the skull was massive and long, the brain was small; a brontothere probably had limited intelligence. There was a pair of large horns at the front of the animal's skull, united at their base but split toward their apex. The teeth were large but primitive; it is probable that a brontothere could eat only soft vegetation. It is also probable that with the spread of grasslands the titanotheres proved unable to deal with the large amounts of grit that had to be chewed and became extinct because they possessed the wrong kind of tooth construction.