Review of the Oryzomys couesi Complex (Rodentia: Cricetidae: Sigmodontinae) in Western Mexico

The status and distribution of eight species-group taxa of the Oryzomys couesi group (Rodentia: Cricetidae: Sigmodontinae) described from western Mexico are evaluated based on morphological and morphometric comparisons. Four of these are recognized as valid species within the region: Oryzomys albiventer Merriam, 1901 (including molestus Elliot, 1903), from inland plateau of the Mesa de Anáhuac; O. couesi mexicanus J.A. Allen, 1897 (including bulleri J.A. Allen, 1897; lambi Burt, 1934; rufus Merriam, 1901), from Pacific coastal plain, contiguous lower mountain slopes, and interior valleys along the Rı́os Tepalcatepec–Balsas; O. nelsoni Merriam, 1898, from Isla Marı́a Madre; and O. peninsulae Thomas, 1897, from the southern tip of the Baja California Peninsula. Three other taxa named from uplands in interior Mexico— aztecus Merriam, 1901; crinitus Merriam; 1901; and regillus Goldman, 1915—are provisionally retained within O. couesi, but further study of their specific stature and relationships is required. The recommended taxonomic changes within western Mexico serve to discuss directions for future revisionary research that will refine the definition and distribution of O. couesi sensu stricto in Middle America.