Bison occidentalis

Bison occidentalis is an extinct species of bison that lived in North America and the Japanese archipelago from about 11,000 to 5,000 years ago, spanning the 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 other Pleistocene species of bison. Around 5,000 years ago, B. occidentalis was replaced by today's smaller Bison bison. 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. More recently ancient DNA studies have proven interbreeding between B. occidentalis and ancestral modern 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.