Lutetian extinctions

Hyracotherium ( ; "hyrax-like beast") is an extinct genus of small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation. This small, fox-sized animal is (for some scientists) considered to be the earliest known member of Equidae before the type species, H. leporinum, was reclassified as a palaeothere, a perissodactyl family related to both horses and brontotheres. The remaining species are now thought to belong to different genera, such as Eohippus, which had previously been synonymised with Hyracotherium.

Mesatirhinus is a genus of brontothere endemic to North America during the Eocene living from 50.3 to 42 mya, existing for approximately .