Heteromeryx is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of Artiodactyla, of the family Protoceratidae

Protoceratidae

Protoceratidae is an extinct family of herbivorous North American artiodactyls that lived during the Eocene through Pliocene at around 46.2—4.9 Ma., existing for approximately .-Taxonomy:...

, endemic to North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 from the Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 epoch (Duchesnean

Duchesnean

The Duchesnean North American Stage on the geologic timescale is a North American Land Mammal Age , with an age from 42 to 38 million years BP, representing . It falls within the Eocene epoch. The Duchesnean is preceded by the Uintan and followed by the Chadronian NALMA.The Duchesnean falls within...

 to Chadronian

Chadronian

The Chadronian age within the North American Land Mammal Ages chronology is the North American faunal stage typically set from 38,000,000 to 33,900,000 years BP, a period of . It is usually considered to fall within the Eocene epoch...

 stage) 40.2—33.9 Ma, existing for approximately .

Taxonomy

Heteromeryx was named by Matthew (1905). Its type is Heteromeryx dispar. It was assigned to Protoceratidae

Protoceratidae

Protoceratidae is an extinct family of herbivorous North American artiodactyls that lived during the Eocene through Pliocene at around 46.2—4.9 Ma., existing for approximately .-Taxonomy:...

 by Matthew (1905), Carroll (1988), Prothero (1998) and Prothero and Ludtke (2007).

Morpnhology

Heteromeryx resembled deer

Deer

Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...

. However they were more closely related to camelids

Camel

A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...

. In addition to having horns in the more usual place, protoceratids had additional, rostral horns above the orbital cavity

Orbit (anatomy)

In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...

.

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 (94.6 lb)
• Specimen 2: 46.1 kg (101.6 lb)
• Specimen 3: 31.7 kg (69.9 lb)

Fossil distribution

Fossils have been recovered from:

• Big Red Horizon Site, Presidio County, Texas
  Presidio County, Texas
  Presidio County is a county located in the U.S. state of Texas. In 2000, its population was 7,304. Its county seat is Marfa. Presidio County is in the Trans-Pecos region of West Texas and is named for the ancient border settlement of Presidio del Norte.-Geography:Presidio County is triangular in...
  
  
• Dirty Creek Ridge Site, Sioux County, Nebraska
  Sioux County, Nebraska
  -National protected areas:* Agate Fossil Beds National Monument* Nebraska National Forest * Oglala National Grassland -Demographics:...
  
  
• French Creek Site, Custer County, South Dakota
  Custer County, South Dakota
  As of the census of 2000, there were 7,275 people, 2,970 households, and 2,067 families residing in the county. The population density was 5 people per square mile . There were 3,624 housing units at an average density of 2 per square mile...