Richardson's New Guinea mountain rat is known from the high Snow Mountains of western New Guinea. It has very dense fur, while its diet and breeding habits remain poorly documented.
The back has very dense tawny-brown fur mixed with black hairs and reported to exceed about 17 mm. The underside is pale buff with gray bases.
Specimens were collected at 3,225–4,050 m in 1938, and the handbook says the rat appears abundant in the Snow Mountains. Its feeding and reproductive habits are not known in the cited account.
An extinction-risk assessment has not been added yet.