Oligoryzomys Bangs, 1900 . New England Zool. Club., 1:94.

TYPE SPECIES: Oryzomys navus Bangs, 1900 (= Hesperomys fulvescens Saussure, 1860).

COMMENTS: Oryzomyine. Described as a subgenus of Oryzomys and usually recognized as such (Ellerman, 1941; Hall, 1981; Tate, 1932e) or as a genus (Contreras and Berry, 1983; Gyldenstolpe, 1932), with Microryzomys as a full synonym (Gyldenstolpe, 1932; Tate, 1932e) or not (Cabrera, 1961). Diagnosis emended at the generic level by Carleton and Musser (1989). Species-level revisions required: estimates range from one (Hershkovitz, 1966c) to 30 (Tate, 1932e), usually around 12 (Cabrera, 1961). Regional studies have recorded three or four species in sympatry or parapatry (Contreras and Berry, 1983; Massoia, 1973; Myers and Carleton, 1981; Olds and Anderson, 1987). Karyology of many species presented in Espinosa and Reig (1991), Gallardo and Patterson (1985), Gardner and Patton (1976), and Myers and Carleton (1981). The species recognized here observe the preliminary review of Carleton and Musser (1989).