Holochilus Brandt, 1835 . Mem. Acad. Imp. Sci. St. Petersbourg, ser. 6, 3(2):428.

TYPE SPECIES: Mus (Holochilus) leucogaster Brandt, 1835 (= Mus brasiliensis Desmarest, 1819).

COMMENTS: Arranged by Hershkovitz (1955a) as one of four genera of sigmodont rodents. Based on reproductive anatomy, Hooper and Musser (1964a) remarked that Holochilus may represent a "well differentiated oryzomyine rather than a sigmodont." Standard karyotypic data have provided little resolution of generic affinities (Gardner and Patton, 1976) but g-banded evaluations supported an oryzomyine affiliation (R. J. Baker et al., 1983a). Retained, with Sigmodon proper, in the tribe Sigmodontini by Reig (1984, 1986).

Genus revised by Hershkovitz (1955a), who consolidated 13 nominal species (e.g., Ellerman, 1941) under H. brasiliensis and diagnosed a new one, H. magnus . Subsequent studies have revealed that brasiliensis of Hershkovitz (1955a) is a composite of three or more species (Aguilera and Perez-Zapata, 1989; Gardner and Patton, 1976; Massoia, 1980 a, 1981; Reig, 1986). In general, evidence for the species acknowledged below issues from more localized studies that lack the perspective of a full generic review; these names, distributions, and synonyms must therefore be accepted as tentative pending such a synoptic revision. Association of synonyms basically observes the species classification of Massoia (1980a).