Sthenictis neimengguensis, Tseng & O'Connor & Wang & Prothero, 2009

Tseng, Zhijie J., O'Connor, Jingmai K., Wang, Xiaoming & Prothero, Donald R., 2009, The first Old World occurrence of the North American mustelid (Mammalia, Carnivora), Geodiversitas 31 (4), pp. 743-751 : 746

Sthenictis neimengguensis n. sp. ( Table 1; Figs 2 ; 3)

“ Sthenictis n. sp. ” – Wang et al. (2003): 26.

HOLOTYPE. — IVPP V 15873 , partial right mandible with p1-m1 and partial left mandible with m1 and partial m2 from the same individual. Collected by Xiaoming Wang on 4 August 1998.

ETYMOLOGY. — Neimengguensis refers to Inner Mongolia (Neimenggu in Chinese), where the new species was discovered.

TYPE LOCALITY. — Locality 346 (formerly 356) of the Tairum Nor locality area (43°24’45.3”N, 113°06’50.9”E), middle channel sandstone of the Tunggur Formation, Inner Mongolia, China.

AGE. — ~12.2 Ma, middle Miocene Tunggur Formation ( Wang et al. 2003).

DIAGNOSIS. — A medium-sized species of Sthenictis ; most similar in morphology to S. dolichops but with narrower p4 and m1, and shallower jaws; larger in overall size than S. bellus , S. robustus , and S. junturensis ; smaller than S. lacota , with narrower premolars and first molar; p1-p4 simple as in other species of Sthenictis ; p4 posterior accessory cusp present.

DESCRIPTION

The holotype specimen (IVPP V15873 ) is best represented by the right mandible which has complete p1 to m1 preserved. The total mandibular length is 84.83 mm; the tooth row length is 44.61 mm from p1 to m1. The mandible is close to twice the m1 crown height immediately ventral of the m1 ( Fig. 2 ). The p1 is reduced to one small, simple cusp. The p2 is small and slender, the anterior half reduced. The p3 is nearly symmetrical; p1 through p3 are unornamented. The p4 is larger than the p3 and very similar in shape with the exception of a well-developed posterior accessory cusp. The m1 of S. neimengguensis n. sp. shows greater lateral compression relative to other species of Sthenictis (Fig. 3). The m1 talonid is slightly trenchant, with the labial border higher than the lingual side; the posterior slope of the protoconid and the anterior slope of the hypoconid form an angle slightly less than 90° while the posterior slope of the metaconid forms a U-shape with the lingual margin of the talonid. The m1 hypoconid is moderately developed. The partial left mandible bears a complete m1 which is the only tooth preserved in the specimen. There are two roots exposed at the position of the p4. The m2 is poorly preserved but is clearly single-rooted. The examination of tooth enamel using the method outlined in Stefen (2001) showed undulating Hunter-Schreger bands throughout the dentition.

Figures

FIG. 2. — Holotype of Sthenictis neimengguensis n. sp., IVPP V15873,right partial dentary:occlusal (in stereo,the stereo pair is A and C), labial (B), and lingual (D) views. Scale bar: 20 mm.