Oligoryzomys nigripes (Olfers, 1818) . In Eschwege, J. Brasilien, Neue Bibliothek. Reisenb., 15:209.

TYPE LOCALITY: Paraguay, Paraguari Dept., Ybycui National Park, 85 km SSE Atyra (as restricted by Myers and Carleton, 1981:14) .

DISTRIBUTION: E Paraguay and N Argentina.

COMMENTS: Neotype designated, diagnosis emended, and karyotype described by Myers and Carleton (1981). Distributional extent unclear; relationship to allopatric forms such as eliurus and longicaudatus warrants investigation. Myers and Carleton (1981) recommended that Mus longitarsus Rengger, 1830, which could apply to either O. microtis or O. nigripes, be considered a nomen dubium.