Akodontini. Studies of electromorphic and gene-sequence variation decisively support the monophyly of Oxymycterus (minus iheringi, see Brucepattersonius) and its tribal placement as an akodontine (D’Elía, 2003; D’Elía et al., 2003; Hinojosa et al., 1987; Hoffmann et al., 2002; Patton et al., 1989; Smith and Patton, 1993, 1999); according to cytochrome b data, a sister group to the Necromys Thaptomys Akodon clade (Smith and Patton, 1999) or to Juscelinomys (D’Elía, 2003; D’Elía et al., 2003). Studies addressing the morphological definition of Oxymycterus include Carleton (1973), Hooper and Musser (1964a), Hinojosa et al. (1987), Vorontsov (1967), and Voss and Linzey (1981). Diploid number of species thus far karyotyped (ca. 8) have proven to be identical (2n = 54, FN = 64) (Bonvicino et al., 1998b; Pereira et al., 2001; Vitullo et al., 1986).
Specific taxonomy needs full published revision, including emended diagnoses of valid taxa, objective criteria for attributed synonyms, and vouchered documentation of ranges. Nominal species here recognized discordantly assimilate Cabrera’s (1961) classification, Reig’s (1987) provisional tally of valid forms (based on his examination of BMNH types), and recent descriptions by Hinojosa et al. (1987), Hershkovitz (1994, 1998), and Hoffmann et al. (2002). Generic characters, nomenclatural foundation of described forms, and natural history reports were compiled by Hershkovitz (1994).