Gracile Thomasomys is a small rodent known from high-elevation forests of southeastern Peru. Detailed natural-history information is limited.
Its back is dark grayish buff to clay-colored, with long, dense, soft fur. The underside is a duller grayish buff; the ears are large and dark, and the tail is longer than the body.
Detailed natural history has not been published. J. L. Patton’s field notes, summarized in the book, report eight ground-trapped specimens, mostly in elfin forest and others on steep slopes.
An extinction-risk assessment has not been added yet.