Brontotherium: Eocene Herbivore

Brontotherium was a large, heavily-built distant relative of rhinoceroses that lived during the late Eocene and early Oligocene Epochs of the Cenozoic Era. Fossilized remains of brontotherium have been found in South Dakota and Nebraska. First discovered by Sioux Indians, the beasts were thought to produce thunderstorms by running across the clouds, hence the name brontotherium which means "thunder beast." They were highly successful herbivores whose range included North America, Asia, and Europe.

Though it resembles rhinos in its appearance, brontotherium was much larger than even the biggest rhino alive today. A large male was about sixteen feet long and eight feet tall, weighing in at nearly five tons. Brontotherium had four hoof-like toes on the front legs and three on the back legs, which were slightly larger. It had a large, forked "horn" on the front of its head that makes it look somewhat like a modern rhino. However, this projection was not made out of matted hair or horn, but rather of bone. This would have made it ill-suited for combat or during courtship contests between males because it would shatter easily. Instead, it was probably used for display purposes only during the mating season. A male with a larger crest might attract a female more effectively than one with a small crest. Brontotherium's size alone would most likely have protected it from the majority of Eocene predators. However, these herbivores might have banded together in herds in order to protect vulnerable young as well as to migrate collectively to favorable areas of food.

Brontotherium was herbivorous, grazing on shrubs and other short vegetation close to the ground. It had fleshy lips like a modern rhinoceros which allowed it to grasp vegetation and strip it from tougher stems. Housed inside its enormous, thick skull were thick teeth that resemble molars. These were designed to chop and grind the vegetation it ate, aiding in digestion. It is also believed that brontotherium possessed a large tongue which would aid in grinding up soft leaves.

Brontotherium was unable to adapt quickly enough to the changing climate at the end of the Eocene Epoch, when the Earth was becoming hotter and grasses were beginning to replace forests. Smaller mammals would replace the giants of the Eocene and Oligocene in many regions of the world where forests and scrublands were shrinking and vast prairies forming.