Priority of family-group name Sigmodontinae, dating from Sigmodontes Wagner, 1843, established by Hershkovitz (1966c) and Reig (1980). Taxonomic and nomenclatural histories of many forms compiled by Tate (1932a-h). Comprehensive and influential alpha-level classifications presented by Gyldenstolpe (1932), Ellerman (1941), and Cabrera (1961). The studies of Carleton (1980), Gardner and Patton (1976), Hershkovitz (1962, 1966b, c), Hooper and Musser (1964), and Reig (1980, 1981, 1984, 1987) contain information on higher-level relationships and classificatory arrangements. For critical overviews of phylogenetic and biogeographic issues, see Hershkovitz (1966b, 1972), Reig (1981, 1984, 1986), D’Elía (2000, 2003), and Pardiñas et al. (2002). Also see commentaries for Neotominae and Tylomyinae, whose genera were formerly arranged within Sigmodontinae, with or without indication of tribal distinction (Carleton and Musser, 1984; McKenna and Bell, 1997; Musser and Carleton, 1993).
For a paleontological background, see Baskin (1978, 1986), Jacobs and Lindsay (1984), Marshall (1979), Reig (1978, 1984), Pardiñas (1999), Pardiñas et al. (2002), Slaughter and Ubelaker (1984), and Simpson (1980). Especially see Pardiñas (1995, 2000a) for redeterminations of Ameghino’s (1889) many descriptions from Pliocene and Pleistocene beds in Argentina, and Pardiñas et al. (2002) for an encyclopedic review of South American fossil taxa and their bearing on the current systematics and biogeographic history of Sigmodontinae. Within South America, earliest known examples of living genera (Auliscomys, Necromys, and possibly Reithrodon) date from the early Pliocene (Montehermosan Formation), and by the late Pliocene, a greater diversity of genera, living and extinct (Abrothrix, Akodon, Cholomys, Dankomys, Graomys, Panchomys, Scapteromys, Wiedomys), has been recorded (Reig, 1978, 1981, 1994; Pardiñas, 1997, 2000a; Pardiñas and Tonni, 1998; Quintana, 2002). By Pleistocene times, many fossils of living genera and species are known, mainly from deposits in Argentina and Brazil (Pardiñas, 1999, 2000a; Pardiñas et al., 2002). A late Pleistocene site in Ecuador contains not only a representative composition of the extant fauna (Akodon, Anotomys, Microryzomys, Phyllotis, Sigmodon, Thomasomys) but also a new genus (Copemyodon) believed to represent a member of the "Copemyne-Peromyscine group" (Fejfar et al., 1993, 1996). In North America, Sigmodon and its possible ancestor Prosigmodon are known from early Pliocene (late Hemphillian) sites in the S USA and N México (Jacobs and Lindsay, 1981; Lindsay and Jacobs, 1985; Martin, 1979). Certain low-crowned tetralophodont forms from the Pliocene of North America (Bensonomys and Symmetrodontomys) have been interpreted as primitive members of Phyllotini and Akodontini (Baskin, 1978, 1986; Czaplewski, 1987; Korth, 1994; Lindsay and Jacobs, 1985), affiliations dismissed by Reig (1980, 1984) as dental convergence. These contrasting views, and their critical bearing on sigmodontine (and neotomine) phylogeny and biogeography, have yet to be satisfactorily reconciled with fresh empirical analyses and from disinterested viewpoints. Using molecular divergence estimates (assuming an Akodon Necromys split at 3.5 million years ago), Smith and Patton (1999) placed the major radiation of sigmodontines within South America at 10-14 million years ago, an interval harmonious with a middle Miocene appearance and well before late Pliocene landbridge formation, as earlier advocated by Hershkovitz (1966b, 1972d) and Reig (1980, 1984).
Following Thomas (1906d, 1916c, 1917c), sigmodontine genera have been informally or formally arranged into tribes (see discussions in Carleton and Musser, 1989; D’Elía, 2000; Hershkovitz, 1966c; Reig, 1981, 1984; Smith and Patton, 1999; Voss, 1993). Confirmatory evidence for the monophyly and formal employment of these suprageneric groupings is vastly improved—especially for the Akodontini (D’Elía, 2003; D’Elía et al., 2003; Reig, 1987; Smith and Patton, 1991, 1993; Steppan, 1995), Ichthyomyini (Voss, 1988), Oryzomyini (Myers et al., 1995; Patton and da Silva, 1995; Smith and Patton, 1999; Steppan, 1995; Voss and Carleton, 1993; Weksler, 2003), and Phyllotini (Braun, 1993; Olds and Anderson, 1989; Ortiz et al., 2000b; Spotorno et al., 2001; Steppan, 1993, 1995)—but much probing phylogenetic investigation of this kind is yet required.
The tribal affiliations cited here basically conform to Reig (1980, 1981, 1984), as modified by Smith and Patton (1999). Notably, we continue to maintain the Thomasomyini (= Aepeomys, Chilomys, Rhipidomys, and Thomasomys) as distinct from the Oryzomyini (see Thomas, 1906d, 1917c; Hershkovitz, 1966c; Carleton and Musser, 1989; Voss and Carleton, 1993); furthermore, we resurrect Vorontsov’s (1959) Reithrodontini for the (Euneomys (Neotomys Reithrodon)) clade (see comments under Reithrodon). An oxymycterine group, as informally used by Hershkovitz (1966c), was never named, and evidence for such a tribe as phyletically distinct from Akodontini has not been forthcoming (Barrantes et al., 1993; D’Elía, 2003; D’Elía et al, 2003; Reig, 1987; Smith and Patton, 1999). Similarly, the scapteromyines of Hershkovitz (1966c), formalized as Scapteromyini by Massoia (1979b; also Reig, 1980, 1981, 1984, and McKenna and Bell, 1997), appear to be polyphyletic and cladistically interspersed among akodontines in molecular studies to date (D’Elía, 2003; D’Elía et al., in press; Smith and Patton, 1999). On the other hand, a congruent body of evidence reveals that certain genera currently aligned within Akodontini, here parenthetically identified as the Southern Andean clade, may eventually warrant tribal recognition (Barrantes et al., 1993; D’Elía, 2003; D’Elía et al., 2003; Reig, 1986, 1987; Smith and Patton, 1999; Spotorno et al., 1990); this possibility should be pursued and framed within a full and proper diagnosis. An intractable residuum of genera, many of them the "plesiomorphic Neotropical muroids" enumerated by Voss (1993), so far refuses to disclose their genealogical secrets, whether based on morphological or molecular information, and are noted as Sigmodontinae incertae sedis (see Table 1).
Faunal treatises and annotated checklists are becoming more available, providing taxonomic, distributional, and bibliographic compilations for Sigmodontinae, on both continental (Eisenberg, 1989; Eisenberg and Redford, 1999; Emmons and Feer, 1997; Redford and Eisenberg, 1992) and regional scales (Argentina—Braun and Mares [1995b], Chebez and Massoia , Díaz , Díaz and Barquez , Galliari et al. , Heinonen Fortabat and Chebez , Mares et al. [1981b, 1989b, 1997]; Pardiñas et al. [2003b]; Bolivia—Anderson [1993, 1997], Anderson et al. , Salazar-Bravo et al. ; Brazil—Avila-Pires , Fonseca et al. ; Chile— Muñoz-Pedreros ; Colombia—Alberico et al. ; Ecuador—Tirira [1999, 2000]; Panamá—Mendez ; Paraguay—Gamarra de Fox and Martin ; Perú—Pacheco et al. ; Surinam—Husson ; Uruguay—González [2000b, 2001], Mones , Mones and Philippi ; Venezuela—Linares ). The amount of taxonomic detail, extent of specimen documentation, and primary literature attribution presented in the aforementioned works vary greatly.