Distinct from other Calomys in its karyotype and characters of the fur, it is known only from two places in Minas Gerais.

In 1996, Geise and coworkers described a new karyotypic variant of Calomys from Lagoa Santa, Minas Gerais with 36 chromosomes and a fundamental number of 66 autosomal arms (2n = 36, FNa = 66), and a 2007 genetic analysis confirmed that the new variant represents an evolutionary lineage separate from other Calomys species.

The upperparts are yellowish brown, becoming lighter towards the sides; this coloration is sharply delineated from the whitish underparts.

The external ears (pinnae) are small and rounded and have a patch of white hair behind them.

[8] The species is known from two localities in Minas Gerais, southeastern Brazil, near the border of the Atlantic Forest and Cerrado biomes.