Urocyon citrinus, TEDFORD R. H. & WANG X. & TAYLOR B. E., 2009

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 : 73-75

Urocyon citrinus , new species Figure 29C–E; appendix 3

Type: UF 18060, right (fig. 29C–D) and left partial rami with parts of i1–i3 alveoli and c–m2 from Inglis site 1A (early Irvingtonian), Citris County, Florida.

Referred Material: From the type locality: UF 18061 , right mandibular fragment with m1 broken alveolus, m2 and m3 alveoli, and angle of mandible with subangular lobe (fig. 29E) ; UF 18062 , right calcaneum ; UF 18063 , proximal end left tibia ; and UF 18064 , right metatarsal IV from the type locality .

Distribution: Only known from the type locality, early Irvingtonian of Florida.

Diagnosis: A synapomorphy that U. citrinus shares with U. galushai is rounded subangular lobe on the mandibular ramus. Pleistocene and Recent species of Urocyon have a distinctly angular subangular process. We have been unable to recognize any autapomorphies for this taxon, although it clearly belongs to the genus as discussed below.

Differs from U. galushai in the following plesiomorphies: smaller premolars, and larg- er m2 with longer trigonid, stronger paracristid and small paraconid, longer bicuspid talonid with entoconulid, and distinct hypoconulid. Differs from U. minicephalus in the following plesiomorphies: less robust p4; m1 more elongate; and m2 relatively larger, trigonid longer, paraconid small, and talonid longer with distinct entoconulid. Differs from U. c. floridanus in the following plesiomorphies; slenderer p4; m1 narrower, metaconid relatively smaller, protostylid weaker, entoconulid stronger; and m2 lingual border less convex and buccal border less concave, trigonid longer, paracristid stronger, metaconid and protoconid smaller with protoconid situated more posteriorly and nearly opposite metaconid; and talonid relatively wider. Differs from U. c. scotti in the following plesiomorphies: larger m2 with longer trigonid, stronger paracristid, and small paraconid, and wider talonid.

Description and Comparison: The dentition of the type mandibular ramus of U. citrinus has characters in common with both Urocyon webbi and U. minicephalus . The lower premolars of U. citrinus are anteroposteriorly short and tall-crowned and resemble those of both U. webbi and U. minicephalus . The p4 of U. citrinus is less robust than that of the latter. The premolars, however, are more evenly and closely spaced. In both M. macconnelli and U. webbi the p2 is separated from p1 and p3 by an unusually long diastema (see fig. 29N).

Although the m1 of U. citrinus is less robust than that of U. webbi , it is similar in length and unlike the shorter proportioned m1 of U. minicephalus . Moreover, the m1 protostylid in U. citrinus is stronger and comparable to that of U. minicephalus . As in U. webbi , the m1 talonid in U. citrinus is elongate but the entoconid and hypoconid are transversely connected, a derived feature that is shared with U. minicephalus and recent taxa. A hypoconulid or hypoconulid shelf is present as in both U. webbi and U. minicephalus .

The elongate m2 of the type of U. citrinus is primitive and closely resembles that of U. webbi . As in the latter, the m2 protoconid and metaconid are situated posteriorly and the trigonid is long. A tiny paraconid lies at the end of the paracristid in a more labial position than in U. webbi . Furthermore, in both U. webbi and U. citrinus the m2 talonid is long with a small entoconulid, a distinct entoconid and hypoconid, and a small hypoconulid. From the above description it is evident that the m2 of U. citrinus has numerous morphological features in common with U. webbi , all of which are primitive. A strong anterobuccal cingulum on the m2 of U. citrinus extends posteriorly to a welldeveloped protostylid, a derived feature present in some individuals of Metalopex macconnelli as well as Urocyon species.

Interestingly, most of the above primitive features of the m2 of U. citrinus are shared to some degree with the living western gray fox, U. cinereoargenteus scotti (fig. 29L). The m2 of U. c. scotti is also rather elongate and less complex than that of U. c. floridanus (fig. 29B). The m2 protoconid and metaconid tend to be smaller and situated more posteriorly, somewhat similar to that of U. citrinus , with either a small paraconid or a strong paracristid running forward from the protoconid. In general, the m 2 in U. c. scotti is less robust, with both the anterolabial cingulum and the protostylid weaker than in U. minicephalus and U. c. floridanus and more like that of U. citrinus .

The mandibular ramus of U. citrinus is similar to that of U. minicephalus . A frag- mentary mandibular ramus ( UF 18061, fig. 29E) from the type locality has a rounded subangular lobe that is an inwardly turned sharp ridge ventrally as in species of Urocyon except U. galushai .

Discussion: The type of U. citrinus resembles the type of Urocyon webbi , but this is due, for the most part, to retention of primitive features of the Urocyon group. Emphasis is placed on the derived morphological features that U. citrinus shares with other species of Urocyon , such as: the presence of a transverse crest joining the m1 entoconid and hypoconid, the presence of an m1 hypoconulid, and the well-developed mandibular subangular lobe. Interestingly, the dentition of U. citrinus most closely resembles that of U. c. scotti among living gray fox populations, a fact that suggests that this western race retains primitive dental features that were lost or modified in the evolution of the eastern race since the early Pleistocene.