Usually regarded as a subspecies of rufocanus (G. M. Allen, 1940; Ellerman, 1941; Ellerman and Morrison-Scott, 1951; Gromov and Polyakov, 1977; Hinton, 1926a; Howell, 1929; Wang, 2003; Ye et al., 2002). Because adults possess rootless molars, Corbet (1978c) reassociated shanseius with Eothenomys, an allocation followed by Corbet and Hill (1992), Musser and Carleton (1993), and Pavlinov et al. (1995a). Karyotype matches that of other Myodes (Ma and Jiang, 1996). Species revised by Kaneko (1992c), as Eothenomys shanseius, who judged the holotype of jeholicus to be a young example.
Pelage texture, hair length, and color pattern in shanseius, however, are typical of species of Myodes, strikingly unlike the dark brown, short-furred Eothenomys (comparative series in AMNH and USNM). Like other Myodes, female shanseius have four pairs of mammae (one pectoral, one axillary, and two inguinal; USNM 155055 and 175527, both lactating adults), compared with only two inguinal pairs in Eothenomys. Occlusal patterns in shanseius also resemble those of Myodes: particularly the five closed, alternate triangles on m1 (six opposite and medially confluent in Eothenomys); four closed, alternate triangles on m2 (four opposite and confluent in Eothenomys); and M3 with two closed, alternate triangles (two opposite and confluent in Eothenomys). We hypothesize that the rootless condition in shanseius was acquired independently, as is thought to have evolved in the Korean M. regulus and species endemic to Japan (M. andersoni, M. smithii, M. imaizumii), all of which are closely related to M. rufocanus (see those accounts). Evaluation of this generic reallocation using other taxonomic information is needed, including critical exemplar species of both Myodes and Eothenomys.
Geographic distribution of M. shanseius is allopatric to that of the Korean endemic M. regulus (see that account), which it morphologically resembles (Kaneko, 1992c). The M. shanseius M. regulus complex represents a segment of Myodes that occurs south and east of the Gobi desert in China and eastward onto the Korean Peninsula; although those populations have acquired rootless molars, they appear to be phylogenetically closer to rhizodont M. rufocanus.