Okavango Vlei Rat

discussion

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 M 3 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

Order Rodentia - Family Muridae

distribution

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

Order Rodentia - Family Muridae

materials_examined

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

Order Rodentia - Family Muridae

discussion

COMMENTS: Described as a subspecies of irroratus and later elevated by Roberts (1951) to specific level. Viewed as a subspecies of O. angoniensis by Davis (1974), and so ranked in many faunal treatises (e. g., Meester et al., 1986; Misonne, 1974), or continued as a distinct species (Smithers, 1983; Swanepoel et al., 1980), which leaves the matter of their synonymy as inconclusive to date.

Order Rodentia - Family Muridae