Rare Ichnofossil - Three Toed Horse and Extinct Brontotheriid

This rare ichnofossil plate was collected decades ago from a site that has been only recently rediscovered. Most probably, the area was a near-shore shelf along Uinta Lake that existed during the Eocene.

This plate contains two types of tracks, both extremely rare tracks. There are four tracks of an early three-toed horse and two other less distinct tracks of a member of the Brontotheriidae family, extinct mammals belonging to the oOrder Perissodactyla which includes horses, rhinos, and tapirs. While brontotheres probably are most closely related to horses, they looked more like rhinoceroses. Brontotheres were browsers in warm temperate to subtropical environments and ranged from forest to open woodland. The group likely originated in North America during the early-middle Eocene and became extinct in North America by the end of the Eocene. They may have survived in Asia into the middle Oligocene.

Similar small three toed tracks described as extremely rare horse tracks have been found near Soldier Summit as reported in the The Journal of Paleontology (Novermber 1968). The Brontotheriidae tracks are not reported from Soldier Summit.

The early horses had three toes on the rear feet, and four toes on the front. However the fourth toe on the front foot was higher on the foot and not likely to leave an impression.