Parapternodus antiquus Bown and Schankler, 1982

ASHER, ROBERT J., McKENNA, MALCOLM C., EMRY, ROBERT J., TABRUM, ALAN R. & KRON, DONALD G., 2002, Morphology And Relationships Of Apternodus And Other Extinct, Zalambdodont, Placental Mammals, Bulletin of the American Museum of Natural History 2002 (273), pp. 1-117 : 69-70

Parapternodus antiquus Bown and Schankler, 1982

TYPE SPECIMEN: YPM 31169, left dentary with m2–3.

REFERRED MATERIAL: UMMP 81557, right dentary with p4­m2, m2 trigonid broken;

UMMP 81560, right dentary with m2­m3 and base of coronoid process (fig. 48); UMMP 81561, left dentary with a fragmentary incisor root and p4­m3 (fig. 49); UMMP 81558, maxillary fragment with left?P3; UMMP 81559, left dentary fragment with lower molar; UMMP 81562, maxillary fragment with right upper molar; UMMP 81563, maxillary fragment with left P4 or M1.

TEMPORAL AND GEOGRAPHIC DISTRIBUTION: Wasatchian (early Eocene) of northern Wyoming (Clark’s Fork Basin 19).

DIAGNOSIS: The talonids of Parapternodus are exceedingly small and form no basin. Anterior to m3, the talonids consist only of a ridge capped by a weak cusp. Parapternodus is slightly smaller than O. cameronensis (contra Bown and Schankler, 1982) and is similar in size to O. altitalonidus . It differs from the latter in having a premolariform p4, an anteroposteriorly short m3 talonid, and mental foramina adjacent to each p4 root. It also lacks buccal cingulids on its lower molars. UMMP 81561 preserves a fragmentary, enlarged root of an anterior incisor that extends posteriorly at least as far as the region below p3. Although no specimen retains an intact coronoid process, the region immediately posterior to m3 on UMMP 81560 and 81561 is not expanded transversely, indicating that the coronoid process is more gracile than that of Apternodus . The base of the coronoid process in UMMP 81650 is excavated deep to the alveolar plane of the dentary, suggesting that like soricids and the larger two species of Oligoryctes , Parapternodus also possessed a coronoid process that was pocketed medially. Alternatively, this excavation could be a dorsally broken entrance for the inferior alveolar nerve and artery; however, we consider this explanation unlikely because of the considerable dorsoventral size of this space and its anterodorsal proximity to the toothrow (fig. 48).

REMARKS: Perhaps due to the fragmentary type material, Bown and Schankler (1982: 67) used some continuous, unquantified comparisons to define Parapternodus , such as ‘‘m2 paracristid and postvallid relatively narrower transversely than in Oligoryctes or Apternodus ... ’’ and ‘‘trigonid less compressed anteroposteriorly than Oligoryctes ’’. These statements cannot be verified based on presently available material. Nevertheless, Bown and Schankler (1982) accurately identified a valid species based on an extremely limited sample, which has improved only slightly since 1982.