Leptomys Thomas, 1897 . Ann. Mus. Civ. Stor. Nat. Genova, 18:610.

TYPE SPECIES: Leptomys elegans Thomas, 1897 .

COMMENTS: Member of the New Guinea Old Endemics (Musser, 1981c). Most lists and faunal studies published since 1951 recognized only one species in Leptomys (Flannery, 1990b; Laurie and Hill, 1954; Menzies and Dennis, 1979; Tate, 1951), but Rummler's (1938) revision in which he identified two species ( elegans and ernstmayri), and Tate and Archbold's (1938) description of a third ( signatus) accurately reflects the known diversity. A derived cephalic arterial pattern, along with other morphological features, is shared by Leptomys, Mayrmys, Neohydromys, Pseudohydromys, and Lorentzimys (Musser and Heaney, 1992). Certain phallic traits (Lidicker and Brylski, 1987), also united Leptomys and Lorentzimys. Chromosomal data were provided by Donnellan (1987), but whether the sampled species was L. elegans or L. ernstmayri is unclear.