M3 occlusal patterns range from slightly more elaborate than Allophaiomys to a configuration resembling N. sikimensis (see Hinton, 1923; Nadachowski and Zagorodnyuk, 1996). The taxon carruthersi was treated as a separate species (Ellerman, 1941; Ellerman and Morrison-Scott, 1951; Ognev, 1964) until synonymized with juldaschi (Corbet, 1978c), a synonymy thereafter observed (Gromov and Erbajeva, 1995; Gromov and Polyakov, 1977; Pavlinov and Rossolimo, 1987, 1998; Pavlinov et al., 1995a; Musser and Carleton, 1993). Bolshakov and Pokrovskii (1969) questioned the morphological distinction of carruthersi and juldaschi and demonstrated unhindered hybridization between the two with completely fertile offspring. Gromov and Polyakov (1977), however, remained skeptical, noting that Bolshakov and Pokrovskii’s sample of carruthersi was not topotypic (Tajikistan, Gissar Mtns, 100 miles east of Samarkand, 9000-10,000 ft) but from the Macha River in the Zeravshan Range, just north of the Gissar Range. Because the specimens used by Bolshakov and Pokrovskii originated from the Maikhur Ravine in the Gissar Valley, and because the type locality is simply given as the Gissar Mtns, we find it reasonable to accept their sample as representative of carruthersi (Ironically, their breeding stock of juldaschi originated from Chechekta in the Pamirs, about 60 km south of the type locality, and drew no criticism).
Gileva and Pokrovskii (1970; and cited references) incorporated past chromosomal results and documented only slight differences between carruthersi from the Gissar Range (2n = 54, FN = 56-58) and M. juldaschi from Chechekta (2n = 54, FN = 60-61). Subsequently, Gileva et al. (1982) substantially broadened their geographic representation, including material from the type locality of juldaschi, and concluded that populations in the Pamirs (juldaschi) and those from the Gissar and Turkestan ranges (carruthersi) formed one group distinct from another complex in the W Tien Shan; whether the two groups represented different species or just geographic variants was not stated (Gromov and Erbajeva, 1995, regarded all as one species). While the status of the western Tien Shan population invites resolution, the published evidence portrays carruthersi and juldashi as examples of the same biological entity.