Brontotheriidae, also called
Titanotheriidae, is a
family of
extinct mammals belonging to the order
Perissodactyla, the order that includes
horses,
rhinoceroses, and
tapirs. Superficially they looked rather like
rhinos, although they were actually more closely related to horses. They lived around 56–34 million years ago, until the very close of the
Eocene.