Oxymycterus rufus (Fischer, 1814) . Zoognosia, 3:71.

TYPE LOCALITY: Argentina, 32.5°S latitude along lower Rio Parana .

DISTRIBUTION: EC Argentina, Uruguay, and SE Brazil.

SYNONYMS: dasytrichus, platensis, rostellatus, rutilans .

COMMENTS: Priority of Mus rufus Fischer, 1814, over Mus rutilans Olfers, 1818, both based on Azara's (1801) descriptions, deserves formal stabilization as does clarification of the morphological identity of the species with Azara's "rat roux." Karyotypes of O. rufus and platensis support their union as one species (Vitullo et al., 1986). Level of relationship to other nominal species and range limits uncertain.

Cabrera (1961) cited Rengger (1830) for the placement of the type locality near Asunción, Paraguay, as it is usually given. Rengger's basis for this interpretation is unclear since Azara (1802) mentioned collecting the species in an arroyo at 32.5 degrees, presumably south latitude, which places the locality somewhere in southern Entre Rios province near the Rio Parana. The origin of the larger, rufescent O. rufus from this region seems more plausible than around Asunción where the smaller, dark-colored O. delator occurs (see Myers, 1982). A future revisor should clarify this discrepancy.