Ash-colored Oldfield mouse
The ash-colored Oldfield mouse is a species of rodent in the genus Thomasomys. It is found in montane forests of the Department of Cajamarca in northern Peru, at elevations of. Until 2023, it was thought to be more widely distributed, ranging into southern Ecuador, but these populations are now identified as three separate, closely related species, T. lojapiuranus, T. pagaibambensis, and T. shallqukucha.
With a head-body length of, Thomasomys cinereus is a medium-sized species for the genus. Distinguishing characteristics compared to its close relatives include, among others:
- Mystacial vibrissae short
- Tail shorter than or equal to head and body
- Tail slightly paler above than below
- Incisive foramina long
- Auditory bullae small