Otomys maximus Roberts 1924

Otomys maximus Roberts 1924, Ann. Transvaal Mus ., 10: 70.

Type Locality: Zambia, Machile River, a northern tributary of the Zambezi (1725Ac quadrant as restricted by Davis, 1974:173).

Vernacular Names: Okavango Vlei Rat.

Synonyms: Otomys davisi Lundholm 1955 .

Distribution: Angola (Crawford-Cabral, 1998:Map 22), SW Zambia, Okavango region of Botswana, NE Namibia (Caprivi Strip), and extreme W Zimbabwe.

Conservation: IUCN – Lower Risk (lc).

Discussion: Described as a subspecies of O. irroratus but Roberts (1951) reconsidered its status as a full species. Thereafter returned to subspecies of O. irroratus (Bohmann, 1952; Ellerman et al., 1953); or viewed as a subspecies of O. angoniensis by Davis (1974), the commonly observed synonymy in faunal and systematic treatises (e.g., Ansell, 1978; De Graaff, 1981; Meester et al., 1986; Misonne, 1974); or continued as a distinct species in others (Corbet and Hill, 1991; Musser and Carleton, 1993; Smithers, 1983; Swanepoel et al., 1980). Based on examinations of AMNH and USNM series from Angola and Botswana, we still favor the last treatment as the best working hypothesis. Although the two are apparently closely related, sharing a nearly occluded or absent stapedial foramen, O. maximus is a larger animal in most external and craniodental measurements (particularly as seen in the robust hindfoot, longer molar row, and deeper mandibular ramus); typically has an M3 with 6 lamina, occasionally 7 (typically 7, occasionally 6 in O. angoniensis); and possesses a dorsal pelage dominated by slate and grayish tones (brown to buffy-brown overtones in O. angoniensis). Smithers (1983) also emphasized the belt of dry, inimical terrain in NE Botwana and SW Zambia that effectively separates the ranges of O. maximus and O. angoniensis . Their consanguinity should be demonstrated using other data sources and comprehensive analyses. Formerly included cuanzensis (see above account).