Tremarctinae

The Tremarctinae or short-faced bears is a subfamily of Ursidae that contains one living representative, the spectacled bear (Tremarctos ornatus) of South America, and several extinct species from four genera: the Florida spectacled bear (Tremarctos floridanus), the North American giant short-faced bears Arctodus (A. pristinus and A. simus), the South American giant short-faced bear Arctotherium (including A. angustidens, A. vetustum, A. bonariense, A. wingei, and A. tarijense) 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 (Arctodus simus and Arctotherium angustidens) 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.

== Taxonomy == Tremarctinae was erected by John Merriam and Chester Stock in 1925. Traditionally, analyses of the phylogenetic inner relationships of tremarctines had Plionarctos and Tremarctos as basal groups with respect to a short-faced bear clade of Arctodus and Arctotherium. A study of the affinities of bears belonging to Arctotherium indicates that they were more closely related to the spectacled bear than to Arctodus, implying convergent evolution of large size in the two lineages. Tremarctines are occasionally referred to as arctodonts and/or arctotheres, or tremarctotheres in older scientific literature.