Metalopex bakeri, 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 : 67-68

Metalopex bakeri , new species Figure 26F–J; appendix 3

Type: F:AM 62970, left partial ramus (fig. 26F–G) with c alveolus, p1 root, p2– p4, mi, m2 alveolus, and associated incomplete frontal (fig. 26J) from the Box T Ranch, Pit 1, Hemphill beds, Ogallala Group (medial Hemphillian), 12 miles northwest of Higgins, Limpscomb County, Texas.

Etymology: Named for C.L. Baker, pioneering geologist of the Cenozoic rocks of the Texas Panhandle early in the 20th Century. His discoveries led to development of the renowned fossil vertebrate faunas of the region.

Referred Materal: F:AM 62971, left maxilla (fig. 26H–I) with C–P3 (alveoli) and P4– M2 from sandy clay, Box T Ranch, West Draw, Hemphill beds, Ogallala Group (medial Hemphillian), 12 miles northwest of Higgins, Limpscomb County, Texas.

Distribution: Only known from the medial Hemphillian of Texas.

Diagnosis: Differs from M. merriami in shorter premolars and shorter premolar row without prominent diastemata except those isolating p2; m1 trigonid short, particularly paraconid, talonid markedly wider than trigonid.

Description and Comparison: The dentition of M. bakeri is marked by numerous autapomorphies. The premolars in the type mandibular ramus are markedly shorter and slightly taller crowned than those of M. merriami . The p2 is separated from p1 and p3 by short diastemata; the diastemata are shorter than those of M. merriami . The m1 is very robust; the width of the talonid is proportionally greater relative to that of the trigonid than in M. merriami . This results in a more wedge-shaped carnassial.

The type consists of a mandibular ramus and the dorsal part of the incomplete frontal bone delimited by sutures with adjacent bones anteriorly and posteriorly. These specimens were found associated and are presumed to be one individual. They serve to complement the information on derived Metalopex that is missing in M. merriami . As in M. merriami , the skull is distinguished by the numerous plesiomorphic features. Anterior to the postorbital process the frontals are relatively flat with a prominent depression adjacent to the processes. The depression is small and almost circular in outline, unlike the larger, more elongate frontal depression in most vulpines. Like the latter, the postorbital process is solid, and the frontal sinus is absent. The posterior part of the nasal-frontal suture is shown in this fragment, which indicates that the nasals reached the level of the posteriormost part of the frontal-maxillary suture. The frontals in M. bakeri show a marked postorbital constriction, as appears to be the case in M. merriami . Like the latter species, the frontal crests join just posterior to the postorbital constriction and well anterior to the frontoparietal suture so that a low sagittal crest is initiated on the frontal bone.

A maxilla (F: AM 62971), referred to M. bakeri , shows the alveoli for the canine through P3. Despite the broken condition of the upper canine alveolus, it is evident that the canine was relatively smaller and more compressed than that of Metalopex merriami . The alveolus for P1 indicates a relatively robust single root. The alveoli for P2 and P3 are very short anteroposteriorly as in the lower dentition. The P2 alveolus is separated from the alveoli of P1 and P3 by diastemata measuring 3.5 and 2.0 mm, respectively. The spacing of the premolars in the maxilla referred to M. bakeri conforms closely to that of the lower premolars in the type. The P4 of M. bakeri is elongate and compressed with a rounded anterolabial corner and a weak lingual cingulum. When compared with M. merriami , the P4 of M. bakeri is similar in form and proportion relative to the molars. Both M1 and M2 are large relative to the carnassial and quadrate in shape as in M. merriami . These molars have a low-crowned paracone and metacone and a strong labial cingulum, but the weak parastyle is separated from the preparacrista rather than joined as in M. merriami . The M1 has a prominent but low protocone, with the postprotocrista running posteriorly to a well-developed metaconule. The hypocone is anteroposteriorly broad, with the lingual cingulum running laterally to join the labial cingulum at the paracone and ending posteriorly at the metacone. The entire perimeter of the m1 is thus surrounded by a well-developed cingulum. M2 has a large and low protocone and a very small metaconule. As in M. merriami , the protocone and metaconule are not connected by the postprotocrista. The hypocone of M2 is also broad anteroposteriorly, and the lingual cingulum extends across the protocone, nearly to the paracone.