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Temporal range: early to middle Miocene 20.43–13.6 Ma
Tomarctus temerarius.JPG
T. temerarius skull, now synonymous of T. brevirostris
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Subfamily: Borophaginae
Tribe: Borophagini
Subtribe: Aelurodontina
Genus: Tomarctus
Cope, 1873
Type species
Tomarctus brevirostris
  • T. brevirostris
  • T. hippophaga
Tomarctus range.png
Range of Tomarctus based on fossil distribution

Tomarctus is a canid genus of the extinct subfamily Borophaginae which inhabited most of North America during the late Early Miocene to the Early Barstovian age of the Middle Miocene (23—16 million years ago). Tomarctus existed for approximately 6.83 million years.

This animal shared a period and ecology with a variety of bear dogs, giant mustelid genera, and the genus of bone-crushing canidae, Cynarctoides. As the bear dogs and giant mustelids became extinct, Tomarctus further radiated to fill a line of dogs which filled the hyena-like fruit eating and bone-crushing niches.


The genus currently contains two accepted species, Tomarctus brevirostris and Tomarctus hippophaga.

Tomarctus brevirostris, synonymous with Aelurodon francisi, was named by Edward Drinker Cope in 1873. Fossil specimens have been found as far south as Panama, east to Plum Point, Maryland, west to California, and north to Montana.[2]

Tomarctus hippophaga was first described by Matthew and Cook in 1909 from the Trojan Quarry, Olcott Formation, Nebraska. Specimens have since been found as far west as California and as far north as the Montana/Alberta, Canada line.[3]


  1. ^ Wang, Xiaoming; Richard Tedford; Beryl Taylor (1999-11-17). "Phylogenetic systematics of the Borophaginae" (PDF). Bulletin of the American Museum of Natural History. 243. Retrieved 2007-07-08.
  2. ^ Paleobiology Database: Tomarctus brevirostris
  3. ^ Paleobiology Database: Tomarctus hippophaga
  • Martin, L.D. 1989. Fossil history of the terrestrial carnivora. Pages 536 - 568 in J.L. Gittleman, editor. Carnivore Behavior, Ecology, and Evolution, Vol. 1. Comstock Publishing Associates: Ithaca.
  • Tedford, R.H. 1978. History of dogs and cats: A view from the fossil record. Pages 1 – 10 in Nutrition and Management of Dogs and Cats. Ralston Purina Co.: St. Louis.
  • - Bio One Data Base - Tomarctus