Hyracotherium (Hyracotherium leporine), was once considered to be the earliest known member of the horse family. Now, though, it is considered to be part of the perissodactyl family related to both horses and brontotheres. Hyracotherium was a dog-sized perissodactyl ungulate that lived in the Northern Hemisphere, with species ranging throughout Asia, Europe, and North America during the Early to Mid Eocene, about 60 to 45 million years ago.

The first fossils of this animal were found in England by the paleontologist Richard Owen in 1841, who suspected that it was a hyrax due to its teeth. He did not have a full skeleton and called it “Hyrax-like beast”. In 1876, Othniel C. Marsh found the full skeleton in America, which he named Eohippus (“dawn horse”). When it became clear that the two finds were closely related, the first published name (Hyracotherium) became official and Eohippus came to be a synonym.

Hyracotherium averaged only 2 feet in length and averaged 8 to 9 inches high at the shoulder. It had 4 hoofed toes on the front feet and 3 hoofed toes on each hind foot. The skull was long, having 44 long-crowned teeth. Hyracotherium is believed to have been a browsing herbivore that ate soft leaves and plant shoots.