Athena Review Image Archive ™
Mesocyon coryphaeus skull
Skull of Mesocyon coryphaeus from side and bottom; arrows show auditory bulla (photo: AMNH)
Mesocyon ("middle dog") was an early canid living in North America during the Oligocene to Early Miocene period (30-20 mya). It belongs to the Hesperocyoninae subfamily of early canids. The first recognized species, M. coryphaeus, was named by Cope in 1879 for fossils in Grant County, Oregon. Fossils of Mesocyon have been also been found in the northern Great Plains and southern California.
Mesocyon was about the size of a coyote or medium-sized dog. Based on its dentition, it is the first known canid to have a primarily meat-based diet. The auditory bulla (arrows), a protective cup-like shield for the middle ear, is enlarged, showing an acute sense of hearing.
References:
Wang and Tedford 2008
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