Type species of Pitymys, a taxon sometimes accorded generic status, particularly by European mammalogists and paleontologists (e.g., Corbet, 1978c; Koenigswald, 1980; Repenning, 1983, 1992; Van der Meulen, 1978). Pitymys is more often viewed as a subgenus of Microtus (e.g., Chaline et al., 1999; Gromov and Polyakov, 1977; Hall, 1981; Miller and Kellogg, 1955), a relationship and ranking convincingly endorsed by a variety of morphological, chromosomal, and molecular studies (Carleton, 1981; Conroy and Cook, 2000a; Conroy et al., 2001; Hooper and Hart, 1962; Modi, 1996; Moore and Janacek, 1990; Zagorodnyuk, 1990).

Van der Meulen (1978) regarded nemoralis and parvulus as species distinct from pinetorum, an evaluation shared by Repenning (1983) and Brunet-LeComte and Chaline (1992) for nemoralis; R. A. Martin (1991) did not view parvulus as separate. Whitaker and Hamilton (1998), on the other hand, regarded both taxa, and other eastern forms, as inseparable from M. p. pinetorum. Such disparate conclusions cry out for critical examination with a broader array of information bases, such as chromosomal and genetic surveys (e.g., Moore and Janecek, 1990; Wilson, 1984). Pitymys hibbardi, a late Pleistocene Floridian form, synonymized with M. pinetorum by R. A. Martin (1995). See Smolen (1981, Mammalian Species, 147).