The Tremarctinae or short-faced bears is a subfamily of Ursidae that contains one living representative, the spectacled bear of South America, and several extinct species from four genera: the Florida spectacled bear, the North American giant short-faced bears Arctodus, the South American giant short-faced bear Arctotherium as well as Plionarctos (P. edensis and P. harroldorum), which is thought to be ancestral to the other three genera. Of these, the giant short-faced bears may have been the largest ever carnivorans in the Americas. The group is thought to have originated in eastern North America, and then invaded South America as part of the Great American Interchange. Most short-faced bears became extinct at the end of the Pleistocene.