Hayoceros 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 the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Antilocapridae, 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...

 during the Early Pleistocene

Early Pleistocene

Calabrian is a subdivision of the Pleistocene Epoch of the Geologic time scale. ~1.8 Ma.—781,000 years ago ± 5,000 years, a period of ~.The end of the stage is defined by the last magnetic pole reversal and plunge in to an ice age and global drying possibly colder and drier than the late Miocene ...

 epoch (1.8 mya—300,000 years ago), existing for approximately .

Taxonomy

Hayoceros was named by Skinner (1942) and named as a subgenus of Tetrameryx by Frick 1937; raised to genus level. It was assigned to Antilocapridae by Skinner (1942) and Carroll (1988).

Morphology

It was about 1.8 metres (5.9 ft) in body length, and, in most respects, resembled modern pronghorns. However, in addition to the pair of forked horn

Horn (anatomy)

A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...

s located above the eyes, as in modern pronghorns, it also possessed a second, longer and unforked, pair on the back of the skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

. Most likely, males used these to fight in a fashion similar to modern pronghorns, locking horns and then pushing until the opponent gave in.