''Merriamoceros'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of pronghorn. It is known from a single species, which is also the type species, ''M. coronatus''.

Discovery and naming

The type specimen (UCMP 20052) that defines this species is named ''Merriamoceros coronatus'' taking after its discoverer, J.M. Merriam. It is known from a partial skull (a single fragmentary horn or antler). Remains of ''Merriamoceros'' were found in rock formations dating to the

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

period, 15.9 to 13.6

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

. Its type locality is Barstow, which is in a Barstovian terrestrial horizon in the Barstow Formation of

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. ''Merriamoceros'' was originally named as a subspecies of ''

Ramoceros ''Ramoceros'' is an extinct genus of the artiodactyl family Antilocapridae endemic to Middle Miocene (Clarendonian) North America.Blount, Kitty and Crowley, Maggie. ''Encyclopedia of Dinosaurs & Prehistoric Life'', p. 271 (Penguin, 2008). Taxon ...

'', but later J. T. Gregory elevated it to a generic level, stating that its palmate style horns were distinct characteristics and required a separate classification. The developmental series discussed by

Childs Frick Childs Frick (March 12, 1883 - May 8, 1965) was an American vertebrate paleontologist. He was a trustee of the American Museum of Natural History and a major benefactor of its Department of Paleontology, which in 1916 began a long partnership wi ...

further supports the hypothesis of homology between the horns of ''

'' and ''Merriamoceros'', with young ''Merriamoceros'' presenting three horns, reminiscent of those of '' Paramoceros''. The horn ontogeny of these two separate genera marks an evolutionarily distinct lineage.

Description

''Merriamoceros'' was a prehistoric relative of modern pronghorn ('' Antilocapra americana''), which is a species of

artiodactyl Artiodactyls are placental mammals belonging to the order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other t ...

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

indigenous to interior western and central North America. Its remains were found in California, and were characterized by a small body size and palmate horns. It is the oldest known member of the

Antilocapridae The Antilocapridae are a family of ruminant artiodactyls endemic to North America. Their closest extant relatives are the giraffids. Only one species, the pronghorn (''Antilocapra americana''), is living today; all other members of the family ...

family, also known as the pronghorns. It was closely related to ''

'' and ''

Merycodus ''Merycodus'' is an extinct genus of the artiodactyl family Antilocapridae. Fossils of this genus have been found in the Santa Fe Group of New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the ...

''. It was, like its relatives, a quadruped herbivore and grazed on the grassy plains of its time. It is not known if ''Merriamoceros'' had any predators and much is still unknown about its paleobiology, but it is assumed that it was similar to the present day pronghorn and its extinct relatives. ''Merriamoceros'' was covered in a short fur and was likely a good runner. ''Merriamoceros'' had some of the most intricate cranial appendages in the family, where the tines were on top and along the outside edges of the horns. Like related species, these were likely initially covered in skin, which gradually rubbed off to expose the bone.

References

Miocene mammals of North America Miocene Artiodactyla Prehistoric pronghorns Monotypic prehistoric Artiodactyla genera {{paleo-eventoedungulate-stub