Protoceratids by willemsvdmerwe-d6n8v9j
An artist's illustration of a Heteromeryx dispar head (top left) compared with other protoceratids
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Protoceratidae
Genus: Heteromeryx
Matthew, 1905
Binomial name
Heteromeryx dispar
Matthew, 1905

Heteromeryx is an extinct genus of protoceratid endemic to North America from the Eocene epoch (Duchesnean to Chadronian stage) 40.2—33.9 Ma, existing for approximately 6.3 million years.


Heteromeryx was named by Matthew (1905). Its type is Heteromeryx dispar. It was assigned to Protoceratidae by Matthew (1905), Carroll (1988), Prothero (1998) and Prothero and Ludtke (2007).


Heteromeryx resembled deer. However they were more closely related to camelids. In addition to having horns in the more usual place, protoceratids had additional, rostral horns above the orbital cavity.

Body mass[]

Three fossil specimens of Prosynthetoceras were measured by M. Mendoza, C. M. Janis, and P. Palmqvist for body mass.

  • Specimen 1: 42.9 kg (95 lb)
  • Specimen 2: 46.1 kg (100 lb)
  • Specimen 3: 31.7 kg (70 lb)