OenomysDivision. After being proposed as a genus by Thomas (1920a), Thallomys was used in checklists (e.g., G. M. Allen, 1939; Ellerman, 1941) until Ellerman et al. (1953) united it with subgenus Aethomys of Rattus. Thallomys was reinstated by Lundholm (1955c), who also suggested it was closely related to Thamnomys. Misonne (1969) pointed out that Thallomys has nothing to do with Rattus, and is most closely related to Tertiary European Parapodemus, an evaluation based on molar occlusal patterns. Analysis of microcomplement fixation of albumin groups Thallomys with Grammomys, Pelomys, Lemniscomys, and Rhabdomys (Watts and Baverstock, 1995a). Although unrelated to Rattus, the phylogenetic position of Thallomys within the diversity of African murines is still unresolved; our allocation to the Oenomys Division must be tested by analyses of gene sequences and suites of morphological traits. Gastric anatomy described by Perrin (1986).

Early checklists and faunal accounts recognized several species (Ellerman, 1941; Roberts, 1951), but for the last 30 years, Thallomys has been either treated as monotypic (D. H. S. Davis, 1965; Meester et al., 1986; Misonne, 1974), or containing two species (F. Petter, 1973a; Skinner and Smithers, 1990). That considerable and significant morphological diversity exists in the genus has been acknowedged. D. H. S. Davis (1965), for example, recognized five groups of subspecies, and F. Petter (1973a) demonstrated that at least two species could be diagnosed. Regional faunal reports of Southern African Subregion mammals discussed presence of two distinct kinds (Skinner and Smithers, 1990; Smithers and Wilson, 1979). Meester et al. (1986) announced the need for revision of Thallomys, and that both morphological and chromosomal data suggested the presence of two species (see Gordon, 1987). Recently, Taylor et al. (1995:59; also see review in Taylor, 2000b) used morphometric analyses of southern African samples that "clearly confirms the existence of two biological species, establishes a reliable morphometric criterion for separating species based on cranial characters, and redefines species distribution limits with a reasonable degree of accuracy." They also noted that "A complete revision of the genus. . . awaits further multidisciplinary studies involving karyotypes, morphometrics, external characters and genetic/molecular studies, based on samples from throughout the range of Thallomys in Africa and including an assessment of all available type specimens." We could not agree more. We list four species. Our review is based on original descriptions of taxa, Roberts' (1951) useful monograph and other regional faunal reports and revisions, large collections of specimens, and holotypes. Thallomys is represented by fossils recovered from late Pliocene and early Pleistocene sediments in East Africa (Denys, 1987a; Jaeger, 1976; Jaeger and Wesselman, 1976; Wesselman, 1984) and Pleistocene formations in South Africa and Namibia (Avery, 1998, 2000; Senut et al., 1992); see review by Denys (1999).