Temporal range: Pleistocene-Holocene
Lucas, 1898 
Bison occidentalis is an extinct species of bison that lived in North America from about 11,000 to 5,000 years ago, spanning the tail end of the Pleistocene to the mid Holocene. Likely evolving from Bison antiquus, B. occidentalis was smaller overall from its ancestor and other species such as the steppe bison. B. occidentalis had a highly variable morphology, and their horns, which pointed rearward, were much thinner and pointed than Pleistocene species of bison. Around 5,000 years ago, B. occidentalis was replaced by today's smaller Bison bison.
It has been theorized that B. occidentalis declined in numbers because of competition with other grass eaters of the megafauna epoch. More recently ancient DNA studies have proven interbreeding between B. occidentalis and ancestral modern bisons, so it was proposed that B. occidentalis was a localized offshoot of B. antiquus and part of the transition from that chronospecies to modern bisons.
- Stephen Austin Hall (1972). "Holocene Bison occidentalis from Iowa". Journal of Mammalogy 53 (3): 604–606. JSTOR 1379052.
- McDonald, J. N. (1981). North American bison: their classification and evolution. Berkeley: University of California Press. ISBN 0520040023.
- Lott, Dale F. (2002). American Bison: A Natural History. Berkeley: University of California Press. ISBN 0-520-23338-7.
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