Borophaginae

The Borophaginae descended from the subfamily Hesperocyoninae. The earliest and most primitive borophagine is the genus Archaeocyon, which is a small fox-sized animal mostly found in the fossil beds in western North America. The borophagines soon diversified into several major groups. They evolved to become considerably larger than their predecessors, and filled a wide range of niches in late Cenozoic North America, from small omnivores to powerful, bear-sized carnivores, such as Epicyon. ==Species==

(top), Aelurodon taxoides (middle), Tomarctus brevirostris'' (bottom). There are 66 identified borophagine species, including 18 newly identified species that range from the Orellan to Blancan ages. A phylogenetic analysis of the species was conducted using cladistic methods, with Hesperocyoninae as an archaic group of canids, as the outgroup. Aside from some transitional forms, Borophaginae can be organized into four major clades: Phlaocyonini, Cynarctina, Aelurodontina, and Borophagina (all erected as new tribes or subtribes). The Borophaginae begins with a group of small fox-sized genera, such as Archaeocyon, Oxetocyon, Otarocyon, and Rhizocyon, in the Orellan through early Arikareean stages. Their good fossil record has also allowed a detailed reconstruction of their phylogeny, showing that the group was highly diverse in its heyday. Noteworthy genera in this group are Aelurodon, Epicyon, and Borophagus (=Osteoborus). According to Xiaoming Wang, the Borophaginae played broad ecological roles that are performed by at least three living carnivoran families, Canidae (which they were a part of), Hyaenidae, and Procyonidae. over 40 million years ==Classification==

Borophagine taxonomy, following Wang et al. (million years=in existence) • Family Canidae • Subfamily †Borophaginae • †Archaeocyon 33—26 Ma, existing • †Oxetocyon 33—28 Ma, existing • †Otarocyon 34—30 Ma, existing • †Rhizocyon 33—26 Ma, existing • Tribe †Phlaocyonini 33—13 Ma, existing • †Cynarctoides 30—18 Ma, existing • †Phlaocyon 30—19 Ma, • Tribe †Borophagini 30—3 Ma, existing • †Cormocyon 30—20 Ma, existing • †Desmocyon 25—16 Ma, existing • †Metatomarctus 19—16 Ma, existing • †Euoplocyon 18—16 Ma, existing • †Psalidocyon 16—13 Ma, existing • †Microtomarctus 21—13 Ma, existing • †Protomarctus 20—16 Ma, existing • †Tephrocyon 16—14 Ma, existing • Subtribe †Cynarctina 20—10 Ma, existing • †Paracynarctus 19—16 Ma, existing • †Cynarctus 16—12 Ma, existing • Subtribe †Aelurodontina 20—5 Ma, existing • †Tomarctus 23—16 Ma, existing • †Aelurodon 16—12 Ma, existing • Subtribe †Borophagina • †Paratomarctus 16—5 Ma, existing • †Carpocyon 16—5 Ma, existing • †Protepicyon 16—12 Ma, existing • †Epicyon 12—10 Ma, existing • †Borophagus (=Osteoborus) 12—5 Ma, existing Cladogram showing borophagine interrelationships, following Wang et al., figure 141: }} ==Extinction==

According to an analysis of the fossil record of North American fossil carnivorans, the decline of borophagines from a diversity of about 30 species 15 million years ago to extinction was largely driven by competition with felids and canines. Climate change, which led to the replacement of North American forests with grasslands, may also have been a factor; borophagines were less suited to running down prey than canines. Although these specific species developed powerful limbs that are capable of cracking bones in vicious pounce attacks, other carnivorous species that rely on quick ambush for catching prey were likely more successful than the slower Borophaginae. ==References==