Pronghorn (Antilocapra americana) Fact Sheet: Taxonomy & History

• Antilo = antelope; capro = male goat
• Pronghorn are the only surviving species of the North American ungulate family Antilocapridae.
• The family to which the pronghorn belongs was originally divided into two subfamilies (one subfamily for extinct Miocene merycodonts and another group of all the other extinct forms plus the modern pronghorn). These distinctions are probably not valid. (Davis 2007)
• Debate remains over whether pronghorn belong in their own family or should be classified in Bovidae (O’Gara & Matson 1975), in Cervidae (Janis & Scott 1987). Recent genetic study says they are closer to Giraffidae forming a sister group to cervids and bovids. (Hernandez et al 2005; Murray 2006)
• Like bovids, pronghorn have horns consisting of a keratinous sheath over a bony core. But unlike bovids whose horn core is permanent, the horn sheath is shed annually and re-grown. Deer antlers don't have sheaths, but the antlers are lost and regrown yearly.
• Five subspecies have been named (based on geography) but genetic evidence suggests only three subspecies should be recognized (Byers 2011).
• Five subspecies named, but only three commonly recognized (Byers 2011; IUCN SSC Antelope Specialist Group 2016)
  • Five subspecies were named because of minor differences in color, size, and location (O’Gara & Yoakum 2004):
    • Antilocapra americana americana – type specimen
    • A. a. oregona – DNA analysis determined this is not genetically distinct from americana, therefore populations in Oregon, California, Idaho, and Nevada should be considered americana (Lee, 1992)
    • A. a. mexicana – more pale coloration, reduced mane, thinner muzzle than americana
    • A. a. peninsularis – facial markings darker, shorter and rougher horns
    • A. a. sonoriensis – smallest subspecies, smaller skull, but little difference from mexicana
  • Mitochondrial DNA analyses since the early 1990s support the idea of clines within a wide-ranging species. (O’Gara and Yoakum, 2004).

• Antilocaprid ancestors most likely evolved in the Old World and migrated to North American during the Late Oligocene. (Davis 2007)
• First antilocaprids seem highly specialized when they appeared in the fossil record, making it difficult to identify an Old World ancestor (O’Gara and Yoakum, 2004).
• Forked or branching horns are a distinguishing feature of the Antilocaprid family. (Davis 2007)
• Pronghorn evolved alongside predators such as dire wolves, the short-faced bear, the North American lion, jaguars, hyenas, and cheetahs; pronghorn were most likely prey for these species (Byers 1997).
• Existing pronghorn’s running speed and endurance are far greater than any living predator; likely that the species evolved these traits in response to evolutionary selection pressures from predators that became extinct at the end of the Pleistocene. (Byers 1997).
• Most anatomical characters used to describe the pronghorn and its fossil relatives seem to place them close to the deer family (Cervidae). (Janis 2000)
• Recent phylogenetic analysis says pronghorn family is closest to Giraffidae, forming a sister group to cervids and bovids, or a sister group to all other horned ruminants.. (Hernandez Fernandez et al 2005; Murray 2006; Janis 2000)

Books

• Built for Speed by John A. Byers, 2003, Harvard University Press
• American Pronghorn: Social Adaptations & the Ghosts of Predators Past by John A. Byers, 1997, University of Chicago Press, Chicago
• Wildlife Society 1998 Book of the Year Award

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Artiodactyla* (or Cetartiodactyla) (even-toed hoofed animals: includes pigs, sheep goats, cattle, deer)

Family: Antilocapridae

Genus: Antilocapra

Species: Antilocapra americana - pronghorn

Subspecies**: A. a. americana - American pronghorn
Subspecies: A. a. mexicana - Sonoran pronghorn
Subspecies: A. a. peninsularis - Baja California pronghorn

Describer: Ord (1815), as Antilocapra americana

*New anatomical and DNA evidence on the relationship between Artiodactyla (even-toed ungulates) and Cetacea (whales and dolphins) recently led to a merging of the two orders into a new group, Cetartiodactyla (Montgelard, 1997; reviewed in Kulemzina, 2009). As of October 2012, experts had not agreed on whether to define Cetartiodactyla as an official taxonomic order that would replace Artiodactyla and Cetacea. Some continue to list okapi in the order Artiodactyla (Franklin, 2011) or use the term Cetartiodactyla without defining it as an order (IUCN, 2008).

**Only three subspecies are commonly recognized (Byers 2011).

The pronghorn is the only surviving species of the North American ungulate family Antilocapridae.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Byers (1997)
Davis (2007)
Hernandez Fernandez et al. (2005)
Murray (2006)
Nowak (1994)
O’Gara & Yoakum (2004)
Janis (2000)