Urocyon Baird, 1858

TEDFORD R. H., WANG X. & TAYLOR B. E., 2009, Phylogenetic Systematics Of The North American Fossil Caninae (Carnivora: Canidae), Bulletin of the American Museum of Natural History 2009 (325), pp. 1-218 : 68-69

Urocyon Baird, 1858

Type Species: Urocyon cinereoargenteus (Schreber), 1775 .

Included Fossil Species: U. progressus Stevens, 1965 ; U. minicephalus Martin, 1974 ; U. webbi , n. sp.; U. galushai , n. sp.; and U. citrinus , n. sp.

Distribution: Medial Hemphillian to Recent in North America and Recent in Central America and northern South America.

Revised Diagnosis: Differs from other vulpines in the following apomorphies: nasals extend posterior to the frontal-maxillary suture; larger more posterieorly extended depression on dorsal surface of postorbital process accentuated by parasagittal ridges that begin at postorbital processes; frontal crests lyrate, strongly ridged, and joining behind frontoparietal suture; frontal part of braincase more expanded with wider postorbital constriction; medial cusplets on I1–I2 absent; canines with short and little recurved crowns; anterolabial cingulum of P4 often produced as parastyle; m1 entoconid and hypoconid usually connected by cristids to form transverse crest, hypoconulid relatively large; m2 trigonid shorter with paraconid varying from small ( U. citrinus ) to absent, talonid narrower with hypoconulid varying from distinct cusp to shelf; and in derived species, horizontal ramus with subangular lobe, condyle above alveolar border, and shallow depression ventral to masseteric fossa.

Discussion: Urocyon is considered the sister taxon of Metalopex . Unlike other vulpines, they have a protostylid on m1 and m2 and a strong labial cingulum on m2 that may be linked with the base of the welldeveloped protostylid. These synapomorphies are evidence of their phyletic relationship.

As listed in the diagnosis, the morphology of the lower molars of Urocyon are more complex, with the consistent presence of the m1 protostylid, the entoconid and hypoconid being generally joined by a transverse crest, and the hypoconulid being larger. The m2 trigonid in Urocyon is very short with the paraconid generally absent, although there is a paracristid. In the most derived species of Urocyon , there is a shallow depression beneath the masseteric fossa, and a prominent subangular lobe is present, which may be keeled ventrally, strongly angled posteriorly, and spinose.