Delomys Thomas, 1917 . Ann. Mag. Nat. Hist., ser. 8, 20: 196.

TYPE SPECIES: Hesperomys dorsalis Hensel, 1872 .

COMMENTS: Thomasomyine. Delomys has variously stood as a genus (Avila-Pires, 1960b; Gyldenstolpe, 1932; Tate, 1932/) or placed within Thomasomys, with or without formal subgeneric division (Ellerman, 1941; Moojen, 1952; Osgood, 1933d). As remarked by Osgood (1933d), Thomas in part created Delomys to taxonomically underscore the geographic disjunction between thomasomyines in SE Brazil and the diverse radiation of typical Thomasomys in the N Andes (e.g., see Reig, 1986). There are features that unite the forms of Delomys, but decision on its classificatory rank—and that of other SE Brazilian endemics like Wilfredomys, Rhagomys, and Phaenomys — must await broader-based phylogenetic inquiry involving Andean thomasomyines.

Number of recognized species listed as four (Moojen, 1952), three (Reig, 1986), two (Ellerman, 1941; Gyldenstolpe, 1932), or one (Corbet and Hill, 1991; Cabrera, 1961), a situation which advises that future list-making would profit from critical specimen examination. Here we recognize two, D. dorsalis and D. sublineatus, following the karyotypic study of Zanchin et al. (1992b). Avila-Pires (1960b) associated Calomys plebejus Winge, 1887, as another form of Delomys; its status with regard to dorsalis and sublineatus warrents clarification.