Hyracotherium ( ; "
hyrax-like beast") is an
extinct genus of very small (about 60 cm in length)
perissodactyl ungulates which was found in the
London Clay formation. This small, dog-sized animal was once considered to be the earliest known member of
Equidae before the type species,
H. leporinum, was reclassified as a
palaeothere, a perissodactyl
family basal 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.