MillardiaDivision. An Indian subcontinental endemic that was incorporated into subgenus Rattus (Ellerman, 1941), then arranged as a valid subgenus within Rattus (Ellerman, 1961; Ellerman and Morrison-Scott, 1951), and finally reinstated as a distinctive genus related to Millardia (Gadi and Sharma, 1983; Misonne, 1969; Raman and Sharma, 1977) and Madromys (see that account).

Evolutionary history as revealed by fossils from Swalik strata in NW India can be traced back to the early Pliocene (identified as Cremnomys sp. and C. cf. cutchicus) and may have been derived from a Progonomys like form, which is the earliest undisputed Miocene murine (Patnaik, 1997, 2001; discussed as Karnimata, which Mein et al., 1993, synonymized with Progonomys). Lower molars from late Pleistocene cave deposits in the Sichuan-Guizhou region of S China were identified as ?Cremnomys sp. by Zheng (1993), which if correct, reflects a wider range for the genus during the Pleistocene.