Subgenus Aschizomys. Stature as species and genus-group allocation highly varied. Retained in Aschizomys as genus by Ellerman (1941). Corbet (1978c) transferred lemminus to Eothenomys, but Russian workers continue to refer it to Alticola (Gromov and Polyakov, 1977; Ognev, 1964; Pavlinov and Rossolimo, 1987). Earlier, Hinton (1926a:279) recognized Aschizomys but speculated that the species is a member of the Myodes rufocanus group; Miller (1940a:94) identified the holotype as "nothing more than an alcohol-discolored specimen of the extreme East Asian representative of Myodes rufocanus," an opinion followed by Ellerman and Morrison-Scott (1951). Some have treated lemminus as a subspecies of A. macrotis (Bolshakov et al., 1985; Gromov and Baranova, 1981; Gromov and Erbajeva, 1995; Gromov and Polyakov, 1977), whereas others have maintained the two as separate (Musser and Carleton, 1993; Pavlinov and Rossolimo, 1987; Pavlinov et al., 1995a). Based on renewed inspection of the holotype, we endorse Ognev’s (1964) allocation of lemminus to Alticola, subgenus Aschizomys, and reemphasize its impressive diagnostic features as a species.
The status of included populations requires additional study. Significant chromosomal and morphological differences between samples from Chukotka and Yakutskaya led Bykova et al. (1978) to speculate that "lemminus" is a composite of two species. Vasil’eva’s (1999:113) analysis of non-metric cranial traits indicated that "A. lemminus probably includes a complex of distinct forms," and interpreted samples from the Chukotka Peninsula, N Yakutskaya, and S Yakutskaya as each representing well defined subspecies. Her evaluation uncovered two major lineages, corresponding to the allopatric ranges of lemminus and macrotis as given here, a division also reflected in a molecular study (Rybnikov et al., 1986); finer divergence patterns within the two major clusters prompted Vasil’eva to suggest "that the taxa and populations under consideration are currently subjected to the process of speciation in statu nascendi." Nikanorov (2000) included A. lemminus among mammals that occur on the Kamchatka Peninsula.