Bison antiquus is an extinct species of bison that lived in North America during the Pleistocene epoch. This prehistoric animal is commonly known as the ancient bison and is closely related to the modern American bison. There are several synonyms for Bison antiquus, including the giant bison, long-horned bison, and the Pleistocene bison. The giant bison is a reference to the large size of this ancient animal, which could weigh up to 2,000 pounds. The long-horned bison is named after its distinctive curved horns, which could span over six feet. Finally, the Pleistocene bison is a reference to the geological epoch in which these creatures roamed the earth.