Synonyms. Uromys nero Thomas, 1913; U. scaphax Thomas, 1913;?u. waigeoensis Frechkop, 1932.

Type material. HOLOTYPE, Leiden Museum (no number), collected at Sentani Lake (2037'S 141°30'E), Irian Jaya, by the Humboldt Bay Expedition on April 18, 1903.

Revised diagnosis. Can be distinguished from other subspecies as follows: i) tail much shorter than head and body; ii) hindfoot short (18-22% of head and body); iii) size small as in U. c. papuanus (condylobasallength 57-64 mm; iv) head and body 273-310 mm, see Table 2); v) feet diffusely white above; vi) tail yellow under base with very little (maximum one third) of its length white above, very little or no mottling, tail scales in clear rings; vii) fur tends to be soft, thick, with grizzling due to yellow or red brown tips to hairs; viii) frontals flat; ix) bullae rounded.

Discussion. There are differences between the type series of U. nero and the juvenile holotype of U. multiplicatus and others of this subspecies (those from the Setakwa and Mimika Rivers, Alkmaar and Bivak Island), the former being darker and of larger size. This may represent simple clinal changes with increasing altitude. The holotype of U. waigeoensis is described as being very large (head and body length 370 mm), but no other differences from the present subspecies seem apparent.

Distribution. This subspecies is distributed throughout mainland Irian Jaya, possibly including Waigeo Island.

Related taxa of uncertain status. Uromys siebersi Thomas, 1923, is from the Kei Islands. This poorly known taxon (known from two skins and a single skull) exhibits a mosaic of features that make it difficult to determine whether it should be placed with U. c. caudimaculatus or U. c. papuanus, or recognised as a distinct subspecies. On the basis of metrical characters it falls near the south-west New Guinean samples. On the basis of its pelage colouration, tail and skull morphology, however, it is very close to Aru Islands U. c. caudimaculatus, differing in that it is slightly smaller, the tail is slightly more mottled at the transition, and the frontals are less convex. In these features it resembles U. c. papuanus. Thus it is intermediate between these two subspecies.

The single specimen known from Yapen Island (to the north of New Guinea) also somewhat resembles U. c. caudimaculatus from the Aru Islands on morphology, and falls within that subspecies on the basis of metrical characters. Because it is represented by only a single specimen, the allocation of the Yapen form must remain uncertain at present.