New findings on the karyotype and distribution of two Rhipidomys Tschudi, 1845 species (Rodentia: Sigmodontinae) from Upper Purus River

Rhipidomys is a Sigmodontinae genus with a great diversity in western Amazonia, including Rhipidomys gardneri and Rhipidomys leucodactylus. These species shared the same diploid number of 44, however, two fundamental numbers were attributed to R. leucodactylus and one to R. gardneri. A new karyotype for R. leucodactylus is described, with a diploid and fundamental number shared by other Rhipidomys species. Data confirmed three karyotypes for R. leucodactylus, only one for R. gardneri, the presence of R. leucodactylus in the Brazilian state of Acre and extend the distribution of R. gardneri to Manoel Urbano, in Acre, showing both species occurring in the high Purus River basin.