The steppe bison (Bison priscus, also less commonly known as the steppe wisent and the primeval bison) is an extinct species of bison which lived from the Middle Pleistocene to the Holocene. During the Late Pleistocene, it was widely distributed across the mammoth steppe, ranging from Western Europe to eastern Beringia in North America. It is ancestral to all North American species of bison, including ultimately the modern American bison (Bison bison). Three chronological and regional subspecies, B. p. priscus, B. p. mediator, B. p. gigas, and B. p. alaskensis have been suggested.
Taxonomy and evolution The steppe bison was first named in 1825 by French-German anatomist and naturalist Ludwig Heinrich Bojanus, this publication also notably coined the scientific name of the aurochs (Bos primigenius). The original combination was Urus priscus. Bojanus originally described the species based on series of specimens (syntype) rather than a singular holotype specimen, though he did not describe each specimen individually or provide illustrative figures of them in the paper. In 1918, Hilzheimer decided to make one of the specimens that Bojanus examined, given the name "Example No. 3", as the lectotype specimen, which has been followed by later authors. This specimen, held in the collections of the University of Pavia, is a nearly complete skull from the sediments of the Po Valley in Lombardy, northern Italy. In a 1947 publication, it was stated that at that time "European and Asiatic writers use the name B. priscus almost universally for any fossilized bison skull." Steppe bison are divided into three chronologically successive subspecies, Bison priscus gigas from the early Middle Pleistocene of Siberia and Eastern Europe, Bison priscus priscus from the late Middle Pleistocene spanning from Western Europe to Siberia, and the Late Pleistocene Bison priscus mediator. There is another Steppe bison subspecies that has been suggested, Bison priscus alaskensis, a North American subspecies ranging from Alaska to Texas, though its taxonomic status has been debated. Some consider it a distinct species, Bison alaskensis.
Evolution The steppe bison first appeared during the mid Middle Pleistocene in eastern Eurasia, subsequently dispersing westwards as far as Western Europe. Steppe bison first entered northwest North America (Eastern Beringia, comprising Alaska and Yukon) around 195,000–135,000 years ago during the Penultimate Glacial Period (equivalent to the Illinoian) at the end of the Middle Pleistocene, and then entered central North America at the beginning of the Last Interglacial (Sangamonian) around 130,000 years ago, following the melting of the Laurentide Ice Sheet. A B. priscus population would later evolve into the long-horned bison (Bison latifrons) around 120,000 years ago, and subsequently a population of B. latifrons into Bison antiquus by 60,000 years ago in central North America. B. antiquus is widely considered to be the ancestor of modern American bison (Bison bison). During the Last Glacial Period, steppe bison continued to inhabit Alaska and Yukon, separated from B. latifrons and B. antiquus by the reformed Laurentide Ice Sheet which formed an effective barrier to dispersal by 75,000 years ago, with genetic evidence indicating a second migration of steppe bison into Alaska and Yukon from Asia around 45-21,000 years ago. At the end of the Pleistocene in Eastern Beringia, the steppe bison is suggested to have likely given rise to Bison occidentalis proper.
Description
Resembling the modern bison species, especially the American wood bison (Bison bison athabascae), adult bull steppe bison could likely reach over 2 m (6 ft 7 in) tall at the withers, and over 1,000 kg (2,200 lb) in weight. The steppe bison is also anatomically similar to the European bison (Bison bonasus), to the point of difficulty distinguishing between the two when complete skeletons are unavailable. Like living bison species, the steppe bison had a hump on its back immediately above its front legs. Skulls of steppe bison are distinguished from those living bison and other extinct Bison species by the shape of their horn cores (the bony inner part of the horn). The horn cores of adult steppe bison generally project laterally outwards to the sides and curve upwards towards their tips. The size of steppe bison horn cores varied between subspecies, with the earliest subspecies Bison priscus gigas having horn cores that spread 1.4–2.1 m (4 ft 7 in – 6 ft 11 in) tip to tip, with this breadth progressively declining in later subspecies, down to 0.9–1.36 m (2 ft 11 in – 4 ft 6 in) in Bison priscus priscus, and to less than 0.9 m (2 ft 11 in) in the final subspecies Bison priscus mediator, corresponding with a body size decease between B. priscus gigas and B. priscus mediator, though the average breadth of the tips of the horn cores is still on average larger than those of living bison even in Late Pleistocene steppe bison. The hair of the mummified "Yukagir bison" specimen is similar to living bison, but generally denser with the hair on the head varying from light brown to black depending on position, with the mane being almost black. The body hair of the "Yukagir bison" is generally shorter than the living American bison, consisting of light brown under hairs and black guard hairs.
Palaeoecology
The steppe bison lived on the mammoth steppe, one of the most expansive biomes in Earths history stretching from Spain to Canada and from the Arctic islands to China. It was a highly productive environment being at the productivity theoretical maximum for an ecosystem at its northern location supporting many plants, herbivores and predators. Like other bison species, steppe bison are thought to have lived in herds.
… excerpt ends here. Continue reading the full article.
