Chionomys Miller, 1908 . Ann. Mag. Nat. Hist., ser. 8, 1:97.

TYPE SPECIES: Arvicola nivalis Martins, 1842 .

COMMENTS: Tribe Arvicolini . Although described as a genus, Miller (1912a) later employed Chionomys as a subgenus, a status which became entrenched in the literature (Corbet, 1978c, Krapp, 1982a) with rare dissenters (e.g., Gromov and Polyakov, 1977; Lehmann, 1969). Recent analyses reveal that Chionomys is not part of the monophyletic group containing Microtus (Chaline and Graf, 1988; Graf, 1982; Nadachowski, 1990«; Pavlinov and Rossolimo, 1987; Zagorodnyuk, 1990). Van der Meulen (1978) considered Suranontys to be a junior synonym of Chionontys, but the type species of Suranontys (= Microtus malei) is regarded as a Microtus related to the oeconomus group, not to Chionontys (see Nadachowski, 1990«). New World Microtus longicaudus was referred to Chionontys by Anderson (1960), but a variety of data sources allies the former with Microtus proper (Chaline and Graf, 1988; Graf, 1982). Discussing the origin and phylogeny of Chionontys, Nadachowski (1990«, 1991) suggested that two branches developed in Europe, one leading to C. nivalis, the other to C. roberti and C. gud . All three species are sympatric in the Caucasus (Nadachowski, 1990«). Karyotypic variation among the three species is reported by Sablina (1988) and Zima and Krâl (1984a).