Dollman's Thamnomys has a conspicuous orange-rufous back and long tail. In Rwanda's Nyungwe, every recorded site was near running water.
A field key describes a large arboreal rat with long bright orange-rufous fur on the back, especially the rump, a whitish underside, and a tail longer than the body.
Nyungwe surveys captured five animals at two river-adjacent sites in 2009; later records were also from valleys or sites with running water. The authors report a local association with flowing water.
An extinction-risk assessment has not been added yet.