Gomphos elkema Shevyreva, 1975

MENG, JIN, BOWEN, GABRIEL J., JIE, YE, KOCH, PAUL L., TING, SUYIN, QIAN, LI & JIN, XUN, 2004, Gomphos elkema (Glires, Mammalia) from the Erlian Basin: Evidence for the Early Tertiary Bumbanian Land Mammal Age in Nei-Mongol, China, American Museum Novitates 3425, pp. 1-24 : 4

Gomphos elkema Shevyreva, 1975

REVISED DIAGNOSIS: Similar to other mimotonids but differing from other Glires in having two pairs of lower incisors. Differing from Mimotona in having less transverse upper teeth, separated paracone and metacone, a longer trigonid, and presence of a mesostyle on upper molars and a mesoconid on lower molars. Differing from Anatolmylus in having a shallow horizontal ramus (see also Averianov, 1994). Differing from Mimolagus in being smaller and having higher crowns of cheekteeth with distinctive cusps and ridges.

REFERRED SPECIMENS: IVPP V13509.1, a right mandible with m1–m3; V13509.2, a left mandible with m2–m3; V13509.3, a right mandible with m2–m3; V13509.4, a right maxilla with P4–M2; V13509.5, a left maxilla with P3–M1; V13509.6, right P4–M1; V13509.7, a right mandible with partial incisor; V13509.8, anterior portion of a right mandible with the major incisor and the alveolus of the minor incisor; V13510.1, a right calcaneus; V13510.2, a left astragalus; V13510.3, a right cuboid; and V13510.4, a right navicular. In addition to the numbered specimens, many unnumbered fragmentary jaws without teeth, isolated incisors, four additional naviculars, seven cuboids, 23 complete and partial astragali, 140 complete and partial calcanea from Huheboerhe, and two calcanea from Bayan Ulan were referred to the species.

LOCALITIES AND AGE: Upper beds of the ‘‘Nomogen Formation’’ in the Huheboerhe section, Erlian Basin of Nei­Mongol (Inner Mongolia), China; the Bumban Member of the Naran­Bulak Formation in Tsagan­Khushu, Nemegt Basin; Members II and III in the Gashato Formation, Ulan­Nur Basin of Mongolia ( Dashzeveg and Russell, 1988; Dashzeveg, 1988); and probably the upper part of the Nomogen Formation at Bayan Ulan. The fauna contained in the Bumban Member has been conventionally considered as early Eocene (Dashzeveg, 1988; Ting, 1998), although an alternative hypothesis that the Bumbanian fauna is of Late Paleocene age exists ( Beard, 1998). Gomphos is known only from Bumbanian faunas, by which the beds containing the taxon in Huheboerhe are biostratigraphically correlative to rocks bearing Bumbanian fossils elsewhere on the Mongolian Plateau (see below).