E. melanogaster species group, its largest-bodied member (Kaneko, 1996b). Described as a subspecies of melanogaster, a placement commonly observed throughout the 1900s, less commonly regarded as distinct (G. M. Allen, 1940; Corbet and Hill, 1992; Ye et al., 2002; Zhang et al., 1997). The account of miletus by Thomas (1914c) and of fidelis by Hinton (1923) described examples of the same species, as G. M. Allen (1940) later perceived; pelage coloration and measurements of each holotype fall within the variation observed in the large AMNH and FMNH series from Yunnan and W Sichuan. Kaneko (2002) used mucronatus as the oldest name for this species and included libonotus from NW India as well as samples from C Burma, N Thailand, and N Vietnam; we identify this material as E. melanogaster (see account).
Eothenomys miletus occurs in the same regions as E. melanogaster but is usually larger in body size and cranial dimensions with a strikingly higher cranium; a tawny brown to reddish brown dorsal coat that is soft, thick and long (shorter coat, velvety in texture, dark brown to melanistic in most melanogaster); and gray underparts either frosted or washed with brown to ochraceous hues (stark slate gray in melanogaster, infrequently washed with brown or buff). Particular samples of E. melanogaster (aurora, colurnus, and mucronatus, and those from N Burma, Thailand, and NW Vietnam) may overlap E. miletus in skull length and width, but they lack its deep and robust cranial conformation and large bulla. While an M3 with four lingual salient angles (E. miletus) versus three (E. melanogaster) has been used to separate them (G. M. Allen, 1940; Corbet and Hill, 1992; Hinton, 1923, 1926a), this character works only for specimens of the latter from Sichuan (see E. melanogaster account); furthermore, not all E. miletus possess four lingual angles—of 71 specimens from Yunnan and Sichuan (AMNH, FMNH), 64 have four angles but seven exhibit only three. Both species are recorded from the same localities in Yunnan (G. M. Allen, 1912, 1940; our study) but precise microhabitat information is unavailable. Wu et al. (1989) and Ye et al. (2002) recorded the 2n as 56, with all acrocentric elements.