Whereas Bohmann (1952) included all otomyine species in Otomys, most systematists have accorded the large-bullar forms separate generic status as Parotomys (see below), and we follow Thomas (1918b) in recognizing Myotomys as genus (see subfamily remarks). Roberts (1951) also treated Lamotomys as generically distinct, but cladistic interpretation of allozymic and immunologcial data, albeit limited to few species so far, clearly affiliate its type species laminatus with other Otomys (Contrafatto et al., 1994; Taylor et al., 1989). Oldest known fossil Otomys species date from the middle to late Pliocene (2-3.5 million years ago) in South Africa and from early Pleistocene (1-2 million years ago) in East Africa (see Denys, 1989a; Sénégas, 2001; Sénégas and Avery, 1998). Synonymy of the fossil Prototomys follows the observations of Avery (1998), who noted the marginal distinction of its type species, P. campbelli, from living O. saundersiae.
The species richness and biogeographic diversification within Otomys were grossly obscured by forcing its exceptional morphological variation into the polytypic application of the biological species concept that prevailed over the middle 1900s (e.g., Bohmann, 1952; Dieterlen, 1968; Ellerman et al., 1953; Misonne, 1974; Petter, 1982). Deconstructing these polyphyletic accretions into diagnosable, genetically homogeneous species is much progressed in southern Africa (see Taylor and Kumirai, 2001, for overview) and selectively in other areas (e.g., Dieterlen and Van der Straeten, 1992). As we noted in 1993, the occurrence of greater specific endemism throughout the isolated East African highlands and volcanoes deserves more serious consideration than it has received to date. Persuant to such revisionary attention, the early syntheses of Wroughton (1906), Dollman (1915), and Hollister (1919) offer a sounder foundation from which to address questions of specific status and distribution in the East African region. Such investigations should emphasize comparisons both among mountain ranges and along their slopes, drawing upon topotypic examples to explicitly address taxonomic and biogeographic problems at issue. In particular, the possibility of multiple independent originations (speciation) of otomyines in afro-alpine environments on East African mountain tops should be the working hypothesis to be disproven.