Rhombomylus laianensis, Zhai et al., 1976

MENG, JIN, HU, YAOMING & LI, CHUANKUI, 2003, The Osteology Of Rhombomylus (Mammalia, Glires): Implications For Phylogeny And Evolution Of Glires, Bulletin of the American Museum of Natural History 2003 (275), pp. 1-247 : 18-21

R. laianensis Zhai et al., 1976 .

Rhombomylus cf. turpanensis (Dashzeveg and Russell, 1988) .

LECTOTYPE: V4362 (Dashzeveg and Russell, 1988), a left maxilla with P4­M3.

DISTRIBUTIONS AND AGES: As for the genus.

DIAGNOSIS: Same as that of the genus.

REFERRED SPECIMENS: See Materials and Methods.

COMMENTS: Rhombomylus turpanensis is based on the specimens from the lower Eocene Shisanjianfang Fm., Turpan Basin of Xinjiang. Because Zhai did not designate a type specimen for R. turpanensis, Dashzeveg and Russell (1988) chose an upper dentition (IVPP V4362) as the lectotype for the species. Mammals associated with R. turpanensis include Coryphodon sp. , Hyopsodus sp. , Heptodon tienshanensis , and Anatolostylops dubius ( Zhai, 1978) .

‘‘ Rhombomylus laianensis ’’ was based on a right maxilla with P3­M3 (IVPP V5174), a right lower jaw with p4­m3 (IVPP V5175), and a left lower jaw with m2­m3 (IVPP V5176) from the lower Eocene Zhangshanji Fm. at a site south to the Wangjiagang village, Laian, Anhui Province (Zhai et al., 1976). No other mammal was known from this locality.

The specimens of Rhombomylus from Dajian display a range of size and shape variations owing to individual and ontogenetic variations. We cannot distinguish a systematic pattern among these variations, and therefore we regard all the specimens as belonging to one species. Because the variation displayed by the Dajian specimens convey morphologies that resulted in recognition of R. turpanensis and ‘‘ R. laianensis ’’, we lump all specimens of Rhombomylus reported previously ( Zhai, 1978; Zhai et al., 1976; Dashzeveg and Russell, 1988) and those from Dajian into a single species, R. turpanensis .

The publication date of Rhombomylus presents a priority problem, as already realized by others (Dashzeveg and Russell, 1988; Mc­ Kenna and Bell, 1997). Although ‘‘ R. laianensis ’’ was published first (Zhai et al., 1976), R. turpanensis was clearly designated as the type species of the genus ( Zhai, 1978). It appears that the 1978 paper was expected to be published first, but was long in press. Therefore, we consider the species name R. turpanensis has priority over ‘‘ R. laianensis ’’.

TABLE 2 Measurements of the Upper Teeth of Rhombomylus (in mm). Asterisk (*) indicates estimate.

TABLE 3 Measurements of the Lower Teeth of Rhombomylus (in mm). Asterisk (*) indicates estimate.

TABLE 4

Skull Measurements of Rhombomylus (in mm) dbm, distance between molar rows; iid, inter­infraorbital distance; iod, interorbital distance; lud, length of the upper diastema; mh, mandibular height; sh, skull height; sl, skull length; wbs, width between squamosal edges; wnr, width of narrowest region of the skull roof. Asterisk (*) indicates estimate.