Caryomys Thomas 1911

Caryomys Thomas 1911, Abstr. Proc. Zool. Soc. Lond., 1911: 4.

Type Species: Microtus (Eothenomys) inez Thomas 1908

Species and subspecies: 2 species:

Species Caryomys eva Thomas 1911

Species Caryomys inez (Thomas 1908)

Discussion: Myodini. Thomas (1911 c, d) proposed Caryomys as a subgenus of Microtus to contain the Chinese species eva, inez, and nux (now included in inez; see below). Hinton (1923) at first elevated Caromys to genus but later (1926 a) included it in Evotomys (= Myodes) because he considered the holotypes of eva, inez, and nux to be young examples of E. rufocanus shanseius, a synonymy followed by others (Ellerman, 1941; Ellerman and Morrison-Scott, 1951; Gromov and Polyakov, 1977). A. B. Howell (1929), however, realigned Caryomys as a subgenus of Microtus and adamantly declared inez to be valid and different from any Clethrionomys (= Myodes); G. M. Allen (1940) concurred in recognizing eva and inez as species but in the subgenus Caryomys of Eothenomys. While the specific validity of both is currently accepted (Corbet and Hill, 1992; Kaneko, 1992 c), Caryomys has either remained sequestered in Eothenomys (Corbet, 1978 c; Musser and Carleton, 1993; McKenna and Bell, 1997; Pavlinov et al., 1995 a) or ignored (Corbet and Hill, 1992).

Recent generic resurrection of Caryomys issues primarily from the karyotypic study of Ma and Jiang (1996). Both eva and inez have 2n = 54 with mostly telocentric pairs; all Myodes and Eothenomys sampled have 2n = 56, with one metacentric pair (Ando et al., 1988; Gamperl, 1982; Harada et al., 1991; Iwasa et al., 1999 a, b; Kaneko et al., 1998; Ma and Jiang, 1996; Modi and Gamperl, 1989; Obara et al., 1995; Sokolov et al., 1990; Yoshida et al., 1989). In pelage texture and coloration, teat number (four versus eight in Myodes), and rootless molars, eva and inez resemble Eothenomys (see G. M. Allen, 1940). Their molars, however, match species of Myodes, or as Thomas (1911 d:175) characterized their occlusal patterns, "the teeth with the triangles nearly all closed [like Myodes], instead of being mostly open and connected with each other [as in Eothenomys]" (also see G. M. Allen, 1940; Hinton, 1923, 1926 a).

Karyotypes, an Eothenomys like external morphology and rootless molars, and a Myodes like occlusal pattern identify eva and inez as a monophyletic group (genus), at which rank Caryomys was reviewed by Ye et al. (2002). According to these data, inclusion of eva and inez in either Eothenomys or Myodes would make the latter polyphyletic and undiagnosable; the monophyly of Caryomys and its phylogenetic separation from the latter require critical evaluation.