In most respects, antilocaprids resemble otherruminants. They have a complex, four-chambered stomach for digesting tough plant matter,cloven hooves, and small, forked horns. Their horns resemble those of thebovids, 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 thecannon bones remaining. Antilocaprids have the samedental formula as most other ruminants:0.0.3.33.1.3.3.
The ancestors of pronghorn diverged from the giraffids in theEarly Miocene.[2] This was in part of a relatively late mammal diversification following a climate change that transformedsubtropicalwoodlands into opensavannahgrasslands.[2]
The antilocaprids evolved in North America, where they filled a niche similar to that of the bovids that evolved in the Old World. During theMiocene andPliocene, 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 includeOsbornoceros, with smooth, slightly curved horns,Paracosoryx, with flattened horns that widened to forked tips,Merriamoceros, with fan-shaped horns, andHayoceros, with four horns.[3][4]
^Palmer, D., ed. (1999).The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 280.ISBN1-84028-152-9.
^abcSemprebon, G.M.; Rivals, F. (September 2007). "Was grass more prevalent in the pronghorn past? An assessment of the dietary adaptations of Miocene to Recent Antilocapridae (Mammalia: Artiodactyla)".Palaeogeography, Palaeoclimatology, Palaeoecology.253 (3–4):332–347.Bibcode:2007PPP...253..332S.doi:10.1016/j.palaeo.2007.06.006.
^Janis, Kathleen M. (1998).Evolution of Tertiary Mammals of North America: Volume 1, Terrestrial Carnivores, Ungulates, and Ungulate Like Mammals. Cambridge University Press. p. 496.
^Prothero, Donald R. (2007).The Evolution of Artiodactyls. Johns Hopkins University Press. p. 232.ISBN978-0-8018-8735-2.
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