Temporal range: early Oligocene
Wang, Tedford, & Taylor, 1999
|Range of Rhizocyon based on fossil distribution|
Rhizocyon ("root dog") is an early member of the subfamily Borophaginae, an extinct subgroup of canids that were endemic to western North America during the Whitneyan and Arikareean stages) of the Oligocene epoch, living from ~33.3—20.6 Ma., existing for approximately .
Rhizocyon was similar to a contemporary species, Archaeocyon leptodus, from the Great Plains, but it shows a few subtle differences in the structure of the skull and dentition 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.
Fossil specimens of two individuals' body mass were examined by Legendre and Roth.
- Specimen 1: 1.51 kg (3.3 lb).
- Specimen 2: 1.57 kg (3.5 lb).
- Foree Site, John Day Formation, Wheeler County, Oregon ~30.8—20.6 Ma.
- Longview Ranch Airport, John Day Formation, [Wheeler County, Oregon ~30.8—20.6 Ma.
- North Blue Basin Site, John Day Formation, Grant County, Oregon ~33.3—30.8 Ma.
- Kimberly Member, John Day Formation, Grant County, Oregon ~30.8—20.6 Ma.
- Roundup Flat (aka South Haystack), Grant County, Oregon ~30.8—20.6 Ma.
- S. Legendre and C. Roth. 1988. Correlation of carnassial tooth size and body weight in recent carnivores (Mammalia). Historical Biology
- Wang, Xiaaoming., 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.
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