protohippus

Tabrum (1981) re-described the equids at the Mission Pit and assigned them to six taxa including Merychippus sp., Calippus sp., Protohippus sp., Pliohippus pernix (= lullianus), Pseudhipparion n.

Five taxa of equids were described from the ash bed by Voorhies (2006), including Neohipparion affine, Pseudhipparion gratum, Cormohipparion occidentale, Pliohippus pernix, and Protohippus simus.

The main differences lie in the abundances between Neohipparion, Pliohippus, Protohippus and, of course, Calippus (only present at a one locality).

Mission and Ashfall vary most significantly in the abundance of Neohipparion and Protohippus as well as the absence of Calippus at Ashfall.

Several specimens were identified as Dinohippus; these were determined to be referable to Pliohippus, while a few were referred to Protohippus. Two specimens labeled Calippus were determined to be individuals of Pseudhipparion in later stages of tooth wear.

Calippus and Protohippus (Mammalia, Perossodactyla, Equidae) from the Miocene (Barstovian-Early Hemphillian) of the Gulf Coastal Plain.