Temporal range: Early Miocene–recent
|Pronghorns in Fort Keogh, Montana|
|Family:|| Antilocapridae |
J. E. Gray, 1866
The Antilocapridae are a family of artiodactyls endemic to North America. Their closest extant relatives are the giraffidswith which they comprise the superfamily Giraffoidea. Only one species, the pronghorn (Antilocapra americana), is living today; all other members of the family are extinct. The living pronghorn is a small ruminant mammal resembling an antelope.
In most respects, antilocaprids resemble other ruminants. They have a complex, four-chambered stomach for digesting tough plant matter, cloven hooves, and small, forked horns. Their horns resemble those of the bovids, in that they have a true horny sheath, but, uniquely, they are shed outside the breeding season, and subsequently regrown. Their lateral toes are even further diminished than in bovids, with the digits themselves being entirely lost, and only the cannon bones remaining. Antilocaprids have the same dental formula as most other ruminants: 0.0.3.3.
The antilocaprids are ruminants of the clade Pecora. Other extant pecorans are the families Giraffidae (giraffes), Cervidae (deer), Moschidae (musk deer), and Bovidae (cattle, goats and sheep, wildebeests and allies, and antelopes). The exact interrelationships among the pecorans have been debated, mainly focusing on the placement of Giraffidae, but a recent large-scale ruminant genome sequencing study suggests Antilocapridae are the sister taxon to Giraffidae, as shown in the cladogram below.
The ancestors of pronghorn diverged from the giraffids in the Early Miocene.This was in part of a relatively late mammal diversification following a climate change that transformed subtropical woodlands into open savannah grasslands.
The antilocaprids evolved in North America, where they filled a niche similar to that of the bovids that evolved in the Old World. During the Miocene and Pliocene, they were a diverse and successful group, with many different species. Some had horns with bizarre shapes, or had four, or even six, horns. Examples include Osbornoceros , with smooth, slightly curved horns, Paracosoryx, with flattened horns that widened to forked tips, Ramoceros , with fan-shaped horns, and Hayoceros , with four horns.
Ungulates are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses. Cetaceans such as whales, dolphins, and porpoises are also classified as even-toed ungulates, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving.
The even-toed ungulates are ungulates—hoofed animals—which bear weight equally on two of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, odd-toed ungulates bear weight on an odd number of the five toes. Another difference between the two with the exception of Suina many other even-toed ungulates digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do.
The Bovidae comprise the biological family of cloven-hoofed, ruminant mammals that includes nilgai, bison, African buffalo, water buffalo, antelopes, wildebeest, hartebeest, Common tsessebe, bontebok, hirola, sheep, goats, muskoxen, and domestic cattle. A member of this family is called a bovid. With 143 extant species and 300 known extinct species, the family Bovidae consists of eight major subfamilies apart from the disputed Peleinae and Pantholopinae. The family evolved 20 million years ago, in the early Miocene.
The Giraffidae are a family of ruminant artiodactyl mammals that share a common ancestor with cervids and bovids. This family, once a diverse group spread throughout Eurasia and Africa, presently comprises only two extant genera, the giraffe and the okapi. Both are confined to sub-Saharan Africa: the giraffe to the open savannas, and the okapi to the dense rainforest of the Congo. The two genera look very different on first sight, but share a number of common features, including a long, dark-coloured tongue, lobed canine teeth, and horns covered in skin, called ossicones.
A horn is a permanent pointed projection on the head of various animals that consists of a covering of keratin and other proteins surrounding a core of live bone. Horns are distinct from antlers, which are not permanent. In mammals, true horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae (pronghorn) and Bovidae. Cattle horns arise from subcutaneous connective tissue and later fuse to the underlying frontal bone.
Capromeryx minor, sometimes known as the dwarf pronghorn, is a very small, extinct species of pronghorn-like antilocaprid ungulate discovered in the La Brea Tar Pits of California and elsewhere. It has been found at least as far east as the coast of Texas. It stood about 60 centimetres tall at the shoulders and weighed about 10 kilograms (22 lb). It is unclear whether females had horns as well as males. Each horn consists of a pair of short, straight points that sprout from a single base on either side of the head, with the two prongs parallel rather than diverging as in Tetrameryx and Stockoceros. A number of different species have been described which are likely all the same: Capromeryx furcifer, Capromeryx mexicana and Capromeryx minimus. Capromeryx furcifer would have priority as the proper name for the Late Irvingtonian through Rancholabrean species in which the anterior prong is less than 50% the height of the posterior prong. Its fossils have also been found at least as far east at as the Texas coast, as well as in Nebraska, Kansas, New Mexico, Sonora, Baja California, and near Mexico City. Specimens of this species date to the Late Irvingtonian and Rancholabrean periods. Two earlier species are known: Capromeryx tautonensis from Washington state and from Central Mexico in the Early Blancan, and Capromeryx arizonensis from the Late Blancan in Arizona, New Mexico and Florida. These two earlier species were larger and heavier than the Pleistocene species. It is thought by some biologists that it lived in forests and underbrush, where its small size would have helped it to hide. It is unlikely that it lived in open prairies, since it would not have been fast enough to outrun the predators of that time.
Pecora is an infraorder of even-toed hoofed mammals with ruminant digestion. Most members of Pecora have cranial appendages projecting from their frontal bones; only two extant genera lack them, Hydropotes and Moschus. The name “Pecora” comes from the Latin word pecus, which means “horned livestock”. Although most pecorans have cranial appendages, only some of these are properly called “horns”, and many scientists agree that these appendages did not arise from a common ancestor, but instead evolved independently on at least two occasions. Likewise, while Pecora as a group is supported by both molecular and morphological studies, morphological support for interrelationships between pecoran families is disputed.
Hayoceros is an extinct genus of the artiodactyl family Antilocapridae, endemic to North America during the Pleistocene epoch, existing for about 1.5 million years.
Ossicones are columnar or conical skin-covered bone structures on the heads of giraffes, male okapi, and some of their extinct relatives. Ossicones are distinguished from the superficially similar structures of horns and antlers by their unique development and a permanent covering of skin and fur.
Osbornoceros is an extinct artiodactyl genus of the family Antilocapridae. All antilocaprid species are extinct except for the pronghorn. Osbornoceros osborni is the only known species of the genus Osbornoceros. Osbornoceros lived during the Late Miocene around 7 to 6 million years ago in what is now North America. It is well represented in fossil discoveries, with nearly a dozen specimens having been found to date. All come from the Chamita Formation in a quarry near Lyden, New Mexico, the site of numerous other finds such as that of Chamitataxus, a prehistoric badger that lived at the same time. The holotype specimen of Osbornoceros was discovered in 1937 and many more were found nearby during further expeditions.
The Palaeomerycidae are an extinct family of ruminants in the order Artiodactyla, probably ancestral to deer and musk deer. Palaeomerycids lived in North America, Europe, Africa and Asia from 33 to 4.9 million years ago, existing for about 28 million years; one species was also reported from South America, but its identity as a palaeomerycid was subsequently disputed.
The pronghorn is a species of artiodactyl mammal indigenous to interior western and central North America. Though not a true antelope, it is known colloquially in North America as the American antelope, prong buck, pronghorn antelope, prairie antelope, or simply antelope because it closely resembles the antelopes of the Old World and fills a similar ecological niche due to parallel evolution. It is the only surviving member of the family Antilocapridae.
Ramoceros is an extinct genus of the artiodactyl family Antilocapridae endemic to Middle Miocene (Clarendonian) North America.
Giraffoidea is a superfamily that includes the families Climacoceratidae, Antilocapridae, and Giraffidae. The only extant members in the superfamily are the pronghorn, giraffe, and okapi. The Climacoceratidae are also placed in the superfamily, but were originally placed within the family Palaeomerycidae.
Stockoceros is an extinct genus of the North American artiodactyl family Antilocapridae, known from Mexico and the southwestern United States. Its horns are each divided near their base into two prongs of roughly equal length.
Tetrameryx is an extinct genus of the North American artiodactyl family Antilocapridae, known from Mexico, the western United States, and Saskatchewan. The name means "four [horned] ruminant", referring to the division of each horn near its base into two prongs; in T. shuleri, the rear prong is much longer.
Merriamoceros is an extinct genus of pronghorn. It is known from a single species, which is also the type species, M. coronatus.
Capromeryx was a genus of dwarf pronghorns (Antilocapridae) that originated in North America during the Pliocene about 5 million years ago. The closest living relative and only surviving member of the family is the North American pronghorn. Capromeryx furcifer is one of the smallest artiodactlys known, being 24 inches (61 cm) at the shoulder and 25 pounds (11 kg) in weight.