Calomys tocantinsi is a small rodent endemic to the Cerrado of central Brazil. It has a stripe on its back and a white patch behind each ear. Specimens have been collected in several grassland and woodland settings.
The back is gray-brown with a stripe. A white patch sits behind each ear, and the tail is shorter than the head and body in the original description.
Specimens were collected in gallery forest, Cerrado, grassland, near natural vegetation, and near buildings.
An extinction-risk assessment has not been added yet.