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Temporal range: Early Oligocene–Early Miocene
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Subfamily: Hesperocyoninae
Genus: Mesocyon
Scott, 1890
Type species
Temnocyon coryphaeus
  • M. brachyops
  • M. coryphaeus
  • M. temnodon

Mesocyon is an extinct genus of terrestrial carnivore within the family Canidae, subfamily Hesperocyoninae, which inhabited North America from the Early Oligocene to Early Miocene 38.9—20.6 Ma, existing for approximately 18 million years.[1]

Though a carnivore, dentition suggests this animal was a hypercarnivore or mesocarnivore.[2][3]


Mesocyon was the most basal member of a clade that also includes the genera Cynodesmus, Sunkahetanka, Philotrox, and Enhydrocyon.[4] Mesocyon was named by Scott (1890). It was synonymized subjectively with Enhydrocyon by Swisher (1982). It was assigned to Canidae by Scott (1890), Carroll (1988) and Stevens (1991).


Restoration of Mesocyon (right) and other animals from the Turtle Cove Formation

Two specimens were examined by Legendre and Roth with the first specimen's mass being estimated at 7.4 kg (16.3 lbs). The second specimen's mass was estimated at 7.19 kg (15.8 lbs).[5]

Fossil distribution[edit]

Fossils were uncovered on two sites in north central Oregon. Also, 10 other sites from southern California[6] Colorado, southern Wyoming, and western Nebraska.[7]


  1. ^ PaleoBiology Database: Mesocyon Taxonomy, Species
  2. ^ R. M. Nowak. 1991. Walker's Mammals of the World. Maryland, Johns Hopkins University Press (edited volume) II
  3. ^ Q. Ji, Z.-X. Luo, C.-X. J.R. Yuan Wible, J.-P. Zhang, and J.A. Georgi. 2002. The earliest known eutherian mammal. Nature 416:816-822
  4. ^ Wang, X. 1994. Phylogenetic systematics of the Hesperocyoninae (Carnivora, Canidae). Bulletin of the American Museum of Natural History, 221:1-207.
  5. ^ S. Legendre and C. Roth. 1988. Correlation of carnassial tooth size and body weight in recent carnivores (Mammalia). Historical Biology
  6. ^ Paleobiology Database: List of taxa; California
  7. ^ Paleobiology Database: List of taxa; Tremain, Wyoming