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Temporal range: Early Oligocene–Late Oligocene
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Subfamily: Borophaginae
Genus: Otarocyon
Wang, Tedford, & Taylor, 1999
Type species
Cynodesmus cooki
  • O. cooki
  • O. macdonaldi
Otarocyon range.png
Range of Otarocyon based on fossil distribution

Otarocyon ("large eared dog") is an extinct genus of the family Borophaginae ("bone-crushing dog"). It was a terrestrial canine which was small in size endemic to North America during the Orellan and Geringian stages of the Oligocene epoch, about 33.3—20.6 Ma (million years ago).[1]


Otarocyon was a small borophagine characterized by a short, broad skull, a specialized middle ear, simple, tall premolar teeth, and molars that are incipiently adapted to a hypocarnivore diet. Despite its Oligocene age, the skull of Otarocyon shows several striking similarities to the living fennec fox (Vulpes zerda), particularly in the structure of its middle ear. The similarities are probably convergent, but they suggest that Otarocyon may have been similar in its appearance and habits.[2]


Fossil specimens of two individuals' body mass were examined by Legendre and Roth.[3]

  • Specimen 1: 0.689 kg (1.5 lb)
  • Specimen 2: 0.747 kg (1.6 lb)


  • O. macdonaldi from the early Oligocene (2 mya, Orellan stage. Two specimens weighed 0.703 kg (1.5 lb) and 0.761 kg (1.7 lb)).
  • O. cooki from the late Oligocene (6 mya, Arikareean stage. Two specimens weighed 0.558 kg (1.2 lb) and 0.761 kg (1.7 lb)).

In addition to its earlier age, O. macdonaldi differs from O. cooki in being smaller and in showing lesser development of the specializations that characterize the genus. O. macdonaldi is also the earliest known member of the subfamily Borophaginae, although the later appearing Archaeocyon was more primitive.

Sister genera[edit]

Archaeocyon, Oxetocyon and Rhizocyon.

Fossil distribution[edit]


  1. ^ PaleoBiology Database: Otarocyon Taxonomy, Species
  2. ^ Phylogenetic systematics of the Borophaginae (Carnivora, Canidae)
  3. ^ S. Legendre and C. Roth. 1988. Correlation of carnassial tooth size and body weight in recent carnivores (Mammalia). Historical Biology