Brontotheres, the thunder beasts
Rhino-sized perissodactyls with forked bony horns become the largest land animals of their day.
- When
- —
- Duration
- 16 million years
- Known to
- ± 2 million years
- Era
- Eocene, Cenozoic
Brontotheres start the Eocene at roughly the size of a dog and finish it at the bulk of a large rhinoceros, carrying blunt Y-shaped horns of bone, more likely used for shoving contests than for defence. They are common enough in the North American badlands that Lakota tradition knew their bones as the remains of thunder horses that came down in storms — which is the origin of the name. They die out abruptly at the end of the Eocene, having never evolved teeth for the tougher vegetation that follows.