Rattus omichlodes Misonne 1979

Rattus omichlodes Misonne 1979, Bull. Inst. Roy. Sci. Nat. Belg., Biol., 51: 6.

Type Locality: New Guinea, Prov. of Papua (= Irian Jaya), W Snow Mtns (Pegunungan Maoke), Ertsberg (04E04' S, 137E07' E), 3400 m.

Vernacular Names: Arianus' New Guinea Mountain Rat.

Distribution: Recorded only from western region of Snow Mtns at Ertsberg (3400 m) and Carstensz Peak area, 2950-3950 m (Flannery, 1995 a:340).

Discussion: Rattus leucopus species group. Regarded by Taylor et al. (1982) as identical to R. richardsoni after examining two paratypes of omichlodes (KNMB 4030, 4031), a synonymy followed by Musser and Carleton (1993) who had not studied the type series. Misonne (1979), however, had collected R. richardsoni at the same place but in a different habitat and his comparison with omichlodes clearly indicated the two are different species. Flannery (1995 a;340) revived the latter after finding it in alpine scrub with samples of R. richardsoni and R. arrogans (recorded as R. niobe) in Meren Valley in the Carstensz Peak region; at lower elevations, "[ Rattus] omichlodes occupies boggy alpine heath while [ Rattus] niobe [= R. arrogans] occurs in mossy forest." Flannery had also examined the holotype. Misonne (1979:9) noted that R. arrogans (reported as R. niobe) was common in the forest and lower margins of alpine grassland, that R. richardsoni seemed to be restricted to bushes and grasses above treeline, and R. omichlodes to be still more restricted and found only "in shallow marshes with high grass and small bushes, above treeline." Our recent examination of paratypes of omichlodes (KNMB 4030, 4031) and comparisons with samples in AMNH of R. richardsonii and R. arrogans corroborate Misonne’s original discovery and Flannery’s action. Rattus omichlodes is a different entity than R. richardsoni, but its relationship to R. arrogans has to be resolved in comprehensive morphometric and molecular analyses. From our inspection of specimens, we could not separate the paratypes of omichlodes from the four specimens Flannery sent us from 3950 m in Barren Valley below Meran Glacier, Tembagapura Area, in which he thought two of the specimens represented niobe and two omichlodes . Flannery’s material and the paratypes are thick-furred small-bodied rats the size of R. niobe and much smaller than the large R. arrogans from N slope of the Snow Mtns. This entire complex should be rexamined to redefine omichlodes in relation to the large R. arrogans and series from the S flanks of the Snow Mtns. Our recognition of R. omichlodes is provisional pending a fresh review of the R. niobe complex.