Tremarctinae

Tremarctinae is a subfamily within the bear family Ursidae, commonly known as the short-faced bears. The group includes the living spectacled bear, Tremarctos ornatus, as well as several extinct genera such as Arctodus and Arctotherium. Taxonomic placement varies by authority: some classifications treat Tremarctinae as a distinct subfamily, while others place Tremarctinae as the tribe Tremarctini within Ursinae.

Evolution and distribution evidence suggests that Tremarctinae is a distinct lineage that diverged from other bears during the Miocene to Pliocene. Most analyses place its origin in North America, followed by dispersal into South America during the Great American Biotic Interchange, roughly 3–4 million years ago. The group occupied a wide geographic range across both continents during the Pleistocene, with later extinctions in North America and the extinction of most South American forms except Tremarctos.

The fossil record features several well-known genera. Arctodus, the North American short-faced bears, included some of the largest bears known, with very large skull and limb bones suggesting a massive build. Arctotherium, the South American counterparts, displayed a range of sizes from large to very large. Tremarctos is the genus that includes the living spectacled bear, Tremarctos ornatus, which persists in Andean habitats today.

Ecology and morphology of Tremarctinae are marked by a relatively short snout and robust limbs. Dentition and jaw structure indicate a highly adaptable omnivorous diet, with considerable reliance on fruits, vegetation, and scavenged material; some populations also consumed meat opportunistically. The spectacled bear remains the sole extant member, occupying cloud forests and high-altitude habitats in the Andes.

Conservation status: Tremarctos ornatus is listed as Vulnerable by the IUCN, with threats including habitat loss, fragmentation, and hunting.