These two genera represent divergent approaches toward hypocarnivory. Slightly more derived, but still near the base of the Borophaginae, is the Phlaocyonini, a hypocarnivorous clade of the Arikareean and Hemingfordian that includes Cynarctoides and Phlaocyon. Relationships among these genera are difficult to resolve due to their primitiveness. The Borophaginae begins with a group of small fox-sized genera, such as Archaeocyon, Oxetocyon, Otarocyon, and Rhizocyon, in the Orellan through early Arikareean. Apart from some transitional forms, most of the Borophaginae can be organized in four major clades (all erected as new tribes or subtribes): Phlaocyonini, Cynarctina, Aelurodontina, and Borophagina. The Borophaginae–Caninae clade is in turn derived from the subfamily Hesperocyoninae. At its base, the Borophaginae has a sister relationship with the subfamily Caninae, which includes all living canids and their most recent fossil relatives. A phylogenetic analysis of these species is performed using cladistic methods, with Hesperocyoninae, an archaic group of canids, as an outgroup. A total of 66 species of borophagines, including 18 new species, ranging from Orellan through Blancan ages, are presently recognized. A detailed study of borophagine phylogenetic systematics is presented here, publishing for the first time the entire Frick Collection. As a result of this explosive growth of new information, borophagine systematics is now in need of a complete rethinking at a level that could not have been attempted by previous studies. Largely due to the Childs Frick Collection at the American Museum of Natural History, borophagines are represented by some of the best materials among fossil carnivorans in anatomical representation, sample size, and stratigraphic density. Fossil records of the borophagines are well represented and members of this prolific clade are often the most common predators in the late Tertiary deposits. As a monophyletic group of canids, the Borophaginae is now known to be much more diverse than was originally envisioned but is confined within the middle to late Tertiary of North America.

Simpson in 1945 to include seven genera of large, bonecrushing ‘‘dogs’’ in the late Tertiary of the northern continents.

The subfamily Borophaginae (Canidae, Carnivora, Mammalia) was erected by G.

Dogs by Xiaoming Wang