Bison occidentalis

Bison occidentalis is an extinct species of bison that lived in North America, and potentially in Siberia[2] and the Japanese archipelago[3] from about 11,700 to 5,000 years ago, spanning the end of the Pleistocene to the mid-Holocene.[4]

Bison occidentalis
Temporal range: Pleistocene-Holocene
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Bovidae
Subfamily: Bovinae
Genus: Bison
Species:
†B. occidentalis
Binomial name
†Bison occidentalis
Lucas, 1898 [1]

Characteristics
B. occidentalis skull at Cleveland Museum of Natural History

Likely evolving from Bison antiquus, B. occidentalis was smaller overall from its most direct ancestor, but was similar to the distant ancestor the steppe bison (Bison priscus) in size. B. occidentalis had a highly variable morphology, and their horns, which pointed rearward, were much thinner and pointed than other Pleistocene species of bison.[4]

B. occidentalis, like other bison species, may have existed in small, scattered populations and been unable to increase in numbers until after the Pleistocene epoch ended 10,000 years ago because of competition with other large grazers during the Pleistocene.[5]

Evolution

B. occidentalis's decrease in size from Bison antiquus was likely caused by both human hunting and natural selection.[6] The smaller size likely helped B. occidentalis increase in population after migrating into North America. As Bison antiquus was forced to lived on open grasslands and faced pressure from human hunting, it responded by downsizing into B. occidentalis. Hybridization of these two bison species produced the modern Bison bison, which further decreased body size and increased population.[6] The wood bison (Bison bison athabascae) preserves some original traits of B. occidentalis which was more similar to the ancestral steppe bison, making the wood bison more primitive than the plains bison (Bison bison bison).[2]

More recently ancient DNA studies have proven interbreeding between B. occidentalis and Bison bison, so B. occidentalis was proposed to have been a localized offshoot of B. antiquus and part of the transition from that chronospecies to modern bison.

See also

References
  1. Stephen Austin Hall (1972). "Holocene Bison occidentalis from Iowa". Journal of Mammalogy. 53 (3): 604–606. doi:10.2307/1379052. JSTOR 1379052.
  2. C. G Van Zyll de Jong , 1986, A systematic study of recent bison, with particular consideration of the wood bison (Bison bison athabascae Rhoads 1898), p.53, National Museum of Natural Sciences
  3. Hasegawa, Y.; Okumura, Y.; Tatsukawa, H. (2009). "First record of Late Pleistocene Bison from the fissure deposits of the Kuzuu Limestone, Yamasuge，Sano-shi，Tochigi Prefecture，Japan" (PDF). Bull.Gunma Mus.Natu.Hist. Gunma Museum of Natural History and Kuzuu Fossil Museum (13): 47–52. Retrieved 2018-12-03.
  4. McDonald, J. N. (1981). North American bison: their classification and evolution. Berkeley: University of California Press. ISBN 0520040023.
  5. Lott, Dale F. (2002). American Bison: A Natural History. Berkeley: University of California Press. ISBN 0-520-23338-7.
  6. Valerius Geist, 1996, Buffalo Nation, Voyageur Press


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