Brontotheriidae
Extinct perissodactyls that dominated the Eocene as large herbivores.
Brontotheriidae, commonly known as brontotheres or titanotheres, is an extinct family of perissodactyl (odd-toed ungulate) mammals that lived during the Eocene epoch. Traditionally interpreted as relatives of horses, brontotheres are known from fossils found mainly in Asia and North America, with some remains also discovered in Eastern Europe. Early brontotheres were small, but later forms became the largest land mammals of the Eocene and the largest land mammals to have evolved up until their time. Their rapid diversification and sudden extinction at the end of the Eocene, after roughly twenty million years, has been described as a 'live fast, die young' pattern of evolutionary radiation.
- born
- Eocene epoch
- died
- End of the Eocene epoch
- field
- Paleontology
- known_for
- Extreme size increase, evolution of bony horns, and being among the first fossil mammals from the American West
Lore & Background
The first brontothere fossils known to science were found in South Dakota in the mid-20th century, though earlier discoveries in the White River badlands of South Dakota in 1847 included a jaw described by Hiram A. Prout, who believed it represented remains of giant equoids. The name 'brontothere' was derived from Lakota legends of wakíŋyaŋ, which can be translated to 'thunder beasts'. Joseph Leidy provided early scientific descriptions and named the genera Megacerops and Palaeosyops, though close relations between them were not recognized at the time. Edward Drinker Cope and Othniel Charles Marsh later studied complete brontothere skulls and skeletons; Marsh named the family Brontotheriidae in 1873 and described the genus Brontotherium, now considered a synonym of Megacerops.
Reader's Guide
Brontotheriidae represents a significant chapter in mammalian evolution, illustrating an extreme example of size increase—from early forms like Eotitanops, weighing less than 100 kg, to later four-tonne animals such as Megacerops and Embolotherium. At their peak in the Middle Eocene, brontotheres were the most diverse clade of large mammals in both Asia and North America. Their fossils were among the first mammal fossils from the American West to attract scientific attention, sparking a 'fossil rush'. The group's rapid diversification and sudden extinction at the end of the Eocene highlight a pattern of evolutionary radiation. Current taxonomy recognizes several derived clades, including the horned brontotheres of the subtribe Brontotheriina, whose horns were made of bone and varied in shape and size. The family's legacy includes extensive research by Henry Fairfield Osborn, whose 1929 monograph summarized North American brontothere knowledge.
Did You Know?
- The name 'brontothere' comes from Lakota legends of wakíŋyaŋ, meaning 'thunder beasts'.
- Brontotheres went extinct at the end of the Eocene after roughly twenty million years of existence.
- Later brontotheres, such as Megacerops and Embolotherium, reached weights of four tonnes.
- Brontothere horns were made of bone and occurred in a variety of shapes and sizes.
More in Extinct Cenozoic Mammals 1-24
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