Subgenus Acomys. Qumsiyeh et al. (1986) retained lewisi as a species because fur color and bacular morphology of lewisi are distinctive compared with A. russatus (Atallah, 1967), even though the karyotype of lewisi from Jordan is indistinguishable from A. russatus. However, based on morphological evidence, lewisi was included in A. russatus by other systematists (Corbet, 1978c; Harrison and Bates, 1991; Osborn and Helmy, 1980), an allocation also supported by genetic data (Janecek et al., 1991). See Nevo (1985, 1989, and references therein) for additional chromosomal data and its significance.

Among species of Acomys, A. russatus is very distinctive in its molar morphology (Denys et al., 1994) and chromosomal traits (2n = 66), an isolation bolstered by phylogenetic analysis of mtDNA cytochrome b sequences, which does not associate it closely with any other single species or any species in the A. cahirinus-A. dimidiatus group (Barome et al., 2000, 2001a, b). Acomys russatus and A. dimidiatus are sympatric in Israel and Arabia, and their similarities and differences in ecology, physiology, and activity patterns where they coexist in Israel have been extensively documented (see references in Nevo, 1989).