MicromysDivision. Reviewed by Musser (1972). One of the few murine genera with representatives in both Indochina and on the Sunda Shelf (Musser and Newcomb, 1983). Although molar occlusal patterns are highly derived, they are more similar to those of Chiropodomys than to any other extant Asian murine (Chaimanee, 1998; Misonne, 1969), a suggested alliance supported by shared derived traits of the feet, digits, and skull (Musser and Newcomb, 1983).

Musser and Newcomb (1983) suggested the evolutionary history of Hapalomys to have been confined to Indochina, a view now confirmed by Pleistocene fossils that document a small radiation in the region probably originating in the Pliocene. Isolated molars from early Pleistocene cave sediments in the Sichuan-Guizhou region of S China have been described as H. eurycidens, H. angustidens, and H. gracilis; H. khaorupchangi is represented by molars from early and middle Pleistocene cave deposits on peninsular Thailand (Chaimanee, 1998). A hypothesis of cladistic relationships among three of these extinct and the two living species, based upon molar traits, is provided by Chaimanee (1998).