('thunder beast') is an extinct genus
of prehistoric perissodactyl mammal
of the family Brontotheriidae
, an extinct group of rhinoceros
-like browsers related to horses
. The genus was found in North America
during the Late Eocene
The creature stood 2.50 m (8 ft 4 in) tall at the shoulders and resembled a rhinoceros
, possessing a forked (in a Y, or slingshot
-like protrusion on its nose, with blunt ends. Many Brontotherium
remains have been found in South Dakota
. In the past, specimens exposed by severe rainstorms
were found by Native Americans
of the Sioux
tribe. The Sioux believed these creatures produced thunderstorms
when running over the clouds
, and called them 'thunder horses
'. Many of the skeletons
found by the Sioux belonged to herds
which were killed by volcanic eruptions
of the Rocky Mountains
, which were volcanically active at the time.
Brontotherium's dorsal vertebrae above the shoulders had extra long spines to support the huge neck muscles needed to carry the heavy skull. Possibly, Brontotherium had fleshy lips and a long tongue, perfect for carefully selecting preferred food (soft stems and leaves).
According to Mihlbachler et al. 2004, the species within genus Brontotherium were merged with the genus Megacerops, though not all authorities agree on this.