[2] Some cranial features suggest it may be an archaic relative of the paramo Oldfield mouse (Thomasomys paramorum).

Fine hairs are mixed with flattened and grooved spines that are most numerous on the back.

[3] This rat was first described by Cunha and Cruz in 1979 and is named in honour of the Brazilian naturalist Augusto Ruschi (1915 - 1986).

[5] The fur is agouti (banded in light and dark), and there is little difference in shade between the greyish-yellow upper parts of the animal and the slightly paler underparts.

The type locality is Espírito Santo in southeastern Brazil, and it is also known from several locations in Misiones Province in northeastern Argentina, and from near Rio de Janeiro and in Santa Catarina State.