Subgenus Acomys. Acomys dimidiatus is morphologically very similar to A. cahirinus and with few exceptions (e. g., Ellerman, 1941; Morrison-Scott, 1939; Setzer, 1959, 1975) has usually been listed in the synonymy of that species (Ellerman and Morrison-Scott, 1951; Ellerman et al., 1953; Musser and Carleton, 1993). Volobouev et al. (1996:217) correctly noted "The difficulty to find diagnostic morphological characters is especially notable in the cahirinus-dimidiatus group in which a number of forms and their taxonomic rank are subject to incessant revision." The chromosomal differences "provide a strong cytogenetic isolation" demonstrating the species status of dimidiatus compared with cahirinus, a conclusion they had proposed in an earlier study contrasting chromosomal features among cahirinus, dimidiatus, and airensis (Volobouev et al., 1991). That separation is also indicated by comparative karyological studies (Kunze et al., 1999b; Volobouev et al., 2002b), phylogenetic analyses based on mtDNA cytochrome b gene sequences (Barome et al., 2000, 2001a, b), pericentric satellite DNA (Kunze et al., 1999b), and comparative study of dental traits among species of Acomys (Denys et al., 1994). See Al-Saleh (1988), Barome et al. (2001a), Macholán et al. (1995), Qumsiyeh et al. (1986), Sokolov et al. (1992, 1993), Volobouev et al. (1991), and references cited therein for additional documentation of chromosomal data and its significance. Most samples of A. dimidiatus have 38 chromosomes, but the diploid number is 36 in some populations on the Sinai Peninsula and in Israel, and there is a narrow hybridization zone on the E Sinai (Nevo, 1989; Wahrman and Goitein, 1972; reported as cahirinus). Kronfield et al. (1994) reported ecological characteristics of A. dimidiatus (as cahirinus) and A. russatus where they occur together in S Israel.

Haas’s (1952) carmeliensis was described as a species of Acomys and based upon fragments from prehistoric (Natufian-Neolithic) sediments of Abu Usba Cave in the Mount Carmel region of Israel. Tchernov (1968) regarded the specimens as inseparable from contemporary A. cahirinus in Israel, which was the name applied to the Israeli populations now called A. dimidiatus.