''Rhizocyon'' ("root dog") is an early member of the subfamily

Borophaginae The extinct Borophaginae form one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Hesperocyoninae and extant Caninae. Borophaginae, called "bone-crushing dogs", were endemic to North America d ...

, an extinct subgroup of canids that were endemic to western

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

during the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

epoch, living from ~31—24.5 Ma., existing for approximately . ''Rhizocyon'' was similar to a contemporary species, '' Archaeocyon leptodus'', from the

Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...

, but it shows a few subtle differences in the structure of the

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

and

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology ...

that indicate that ''Rhizocyon'' may be close to the ancestry of later borophagines. Only a single species, ''R. oregonensis'', is known and all fossils come from the John Day Formation in

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

References

* Wang, Xiaoming., R.H. Tedford, and B.E. Taylor. 1999
Phylogenetic systematics of the Borophaginae (Carnivora, Canidae)
Bulletin of the American Museum of Natural History, 243:1-391. * Balisi, Mairin and B. Van Valkenburgh. 2020
Iterative evolution of large-bodied hypercarnivory in canids benefits species but not clades
Communications Biology 3(461). Borophagines Oligocene canids Aquitanian genus extinctions Oligocene mammals of North America Monotypic prehistoric carnivoran genera Rupelian genus first appearances Taxa named by Xiaoming Wang {{canid-stub