Eucyon Tedford & Qiu, 1996

Rook, Lorenzo, 2009, The wide ranging genus Eucyon Tedford & Qiu, 1996 (Mammalia, Carnivora, Canidae, Canini) in the Mio-Pliocene of the Old World, Geodiversitas 31 (4), pp. 723-741 : 726-727

Genus Eucyon Tedford & Qiu, 1996

Tedford & Qiu (1996) named the new genus Eucyon for some primitive Canis -like forms from the late Hemphillian of North America and from the Pliocene of China. The taxon matches closely with the accumulated data on the zoogegraphy and morphology of the late Miocene and early Pliocene s.l. Canis -like dogs, and for the moment represents a convenient and logical taxonomic allocation for Pliocene dog evolutionary history ( Wang et al. 2004a, b; Wang & Tedford 2007, 2008).

According to the diagnosis published by Tedford & Qiu (1996), the genus Eucyon is distinguished from the fossil and living Vulpini by possession of three synapomorphies also possessed by all other members of the Canini : 1) a frontal sinus that invades the base of the postorbital process usually removing the “vulpine depression” on the dorsal surface of the process; 2) a paroccipital process that is expanded posteriorly and usually has a salient tip; and 3) a mastoid process that is enlarged into a knob or ridge-like prominence.

Furthermore, Eucyon lacks a feature characteristic of all other Canini , namely development of a transverse cristid connecting the hypoconid and entoconid of the M 1 talonid. Much attention has been given in the literature to the “simple” talonid structure in the lower carnassial as a feature characteristic of Eucyon . In their phylogenetic analysis of the living Canini , Tedford et al. (1995) clearly demonstrated that within the Caninae , a morphological trend in the M 1 talonid is the increasing dimensions of the entoconid, the base of which may become large enough to coalesce with that of the hypoconid blocking the talonid basin and splitting it into two basins separated by a cristid connecting the two cuspids. The occurrence of this transverse cristid is the final step in the morphocline leading to the carnassial talonid structure typical of living Canini . As a matter of fact, although considered a derived feature of the Canini , most Vulpini have also achieved the same condition and populations of Vulpes Frisch, 1775 and Urocyon Baird, 1857 species may include a sizable proportion of individuals in which the entoconid and hypoconid are joined by cristids from these cusps to form a transverse crest ( Tedford et al. 1995). Thus, it would not be an exception of the possibility to find in Eucyon population, morphotypes with lower carnassial talonid showing the occurrence of a transverse cristid connecting hypoconid and entoconid. In addition to the above traits, Eucyon species have, as an autapomorphy, a second posterior cusplet on the P 4 possessed only by the wolf group among the Canini ( Tedford & Qiu 1996). Further characteristics of the genus are, in the mandible an attenuated (primitive, cf. Gaspard 1964; Tedford et al. 1995) angular process, with insertion for the inferior ramus of the median pterygoid muscle (inferior fossa) not expanded, and in general body proportions, the relative lengthening of the limb bones, especially in the front limbs, with a radius/ tibia ratio usually greater than 80%.

A number of species are nowadays recognised in the literature to be included in the genus Eucyon , with a zoogeographic range across North America, Asia, Europe and Africa. An overview of the species described for the genus is offered herein.

NORTH AMERICA