The rare rodent genus Rhagomys (Rodentia, Sigmodontinae): biogeographical patterns and description of a new species

Rhagomys is a rare Sigmodontinae rodent from South America that includes three known species: R. rufescens, R. longilingua, and R. septentrionalis. These lineages have an intriguing and disjunct geographic distribution, occurring in forest areas in the Andes and Atlantic Forest. These regions are currently separated by the Cerrado and Chaco, two biomes of open vegetation in South America. Despite recent studies, the reduced number of Rhagomys specimens in zoological collections is the main limiting factor for its better systematic understanding. Here, we compile data from the literature and analyze a comprehensive sampling based on an integrative approach to describe a new Rhagomys species, apparently restricted to the Brazilian Atlantic Forest. This new species is diagnosed by a suite of morphological characters, DNA synapomorphies, and its karyotype. Phylogenetic analyses place the new form as sister of the Rhagomys rufescens, its congeneric species from the Atlantic Forest, and apart from the Andean species, showing a current separation between the Andes and the Atlantic Forest lineages.