The dark bolo mouse is recorded in separated areas of eastern Argentina and coastal Uruguay. It uses grassland and damp shore habitats and is often active on the ground by day.
Its back is dark chestnut to blackish brown, with buffy orange tones along the sides. It is large for its genus.
It is often diurnal and moves over the ground, though it also burrows. Its diet includes both invertebrates such as insects and plant material.
An extinction-risk assessment has not been added yet.