Urocyon webbi, 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 : 69-71

Urocyon webbi , new species Figure 29 N–Q; appendix 3

Type: UF 19407, right ramus with c–p1 alveoli and p1–m2 (p3 broken and m3 alveolus, fig. 29N–O) from the Withlacoochee River site 4A (medial Hemphillian), Citrus County, Florida.

Etymology: Named in honor of S. David Webb for his singular contributions to the study of late Neogene mammals of the Americas. We are grateful for his contribution of the type and other important specimens to this study.

Referred Material: From the type locality: UF 19408 , right partial maxilla with P3–P4, and M1–M2 alveoli (fig. 29P–Q) ; UF 20064 , left humerus, UF 13859 , left radius from the location of the type .

Distribution: Only known from the medial Hemphillian of Florida.

Diagnosis: Differs from species of Metalopex in possessing the following apomorphies: P4 with well-developed anterior cingulum and m2 relatively larger with larger paraconid, stronger anterobuccal cingulum and protostylid, and wider talonid with taller crowned entoconid and hypoconid. Great reduction of p2 and associated long diastemata may be autapomorphies for U. webbi . U. webbi is primitive relative to other species of Urocyon , but resembles them in premolar form.

Description and Comparison: The type mandibular ramus of U. webbi is larger and more robust than those of other Urocyon species and lacks the subangular process so characteristic of them. In U. webbi the premolars are anteroposteriorly short, simple, and tall-crowned and remarkably similar to both those of U. minicephalus and U. cineroargenteus floridanus , with the principal difference being the more robust p 4 in U. c. floridanus. Comparison of the P4 ( UF 19408) of U. webbi with that of U. minicephalus and U. c. floridanus shows that the anterior cingulum is well developed, approaching the condition in U. c. floridanus. In Urocyon minicephalus there is a distinct parastyle developed from this cingulum.

Like m1, the m2 of U. webbi closely resembles that of the type of U. citrinus . It is also similar to the m2 of U. cinereoargenteus scotti . Primitive features that separate it from U. citrinus are a more distinct paraconid and a proportionally smaller metaconid relative to the size of the protoconid. Morphologically, the m2 of U. webbi is more like that of U. c. scotti than that of U. minicephalus and U. c. floridanus. It differs from that of U. c. scotti in its distinct paraconid, a more anteriorly situated metaconid, and a wider talonid with a welldeveloped hypoconulid. Compared to the m2 of U. minicephalus , that of U. webbi is more primitive in being more elongate with the outline of the lingual border less convex. Moreover, the m2 of U. webbi also has a distinct paraconid, and the protoconid and metaconid are relatively smaller and situated more posteriorly than in U. minicephalus . In Urocyon webbi , U. citrinus , U. minicephalus , and U. cinereoargenteus floridanus the m2 anterobuccal cingulum is well developed and extends posteriorly across the protoconid to terminate near the well-developed protostylid. Urocyon c. scotti from the southwestern United States retains some of the primitive features found in U. webbi . The protostylid on both m1 and m 2 in U. c. scotti is relatively weak. Furthermore, the m2 trigonid in U. c. scotti is relatively longer with a stronger paraconid crest than in the southeastern taxa of U. citrinus , U. minicephalus , and U. c. floridanus.

The mandibular ramus of U. webbi is similar in general shape to that of Urocyon , but it lacks the subangular lobe. Compared with other species of Urocyon , the horizontal ramus is relatively deeper and markedly deeper beneath p1 and p2. A short diastema isolates p1 from the canine, and a longer diastema isolates the p2. Although the ascending ramus is broken, enough is present to indicate that the masseteric fossa is deep but it lacks the shallow depression ventral to the fossa shown in other Urocyon species.

A humerus ( UF 20064) is referred to U. webbi . It is comparable to that of U. cinereoargenteus except for a smaller entepicondyle and a smaller facet on the trochlea for the articular surface for the capitilum of the radius. In keeping with the latter, a referred radius ( UF 13859) is longer and decidedly more slender than that of similarsized individuals of living Urocyon .