The underparts are white, and there is a clear line separating upper and lower parts.

This species has a range in South America extending from southern Bolivia and northern Paraguay to western and central Brazil.

[1] A study was undertaken in Bolivia to establish which small rodents were reservoir hosts for Leishmania, the causal agent for the human disease leishmaniasis.

[4] Morphological characters and mitochondrial cytochrome b DNA sequences showed that P. longicaudatus belongs to the so-called longicaudatus group of Proechimys species, and shares closer phylogenetic affinities with the other members of this clade: P. brevicauda and P.

The dry forests in this part of South America are being cleared for agricultural purposes and it is thought the population trend of this rat is downwards.