New records and geographic distribution extension of Neusticomys ferreirai and N. oyapocki (Rodentia, Sigmodontinae)

Little is known about the genus Neusticomys, one of the most poorly represented sigmodontine rodents in scientific collections. In this report, we provide new records of Neusticomys ferrerai and N. oyapocki in the Brazilian Amazonia and discuss possible limits for their geographic distributions. Three individuals of N. ferreirai were recorded during three distinct survey events. The first record extends the range of the species approximately 100 km westward, and the other two extend it approximately 1000 km northeastward. For N. oyapocki, our record extends the currently known range of the species approximately 300 km westward. All specimens were collected in primary forests by 60-liter pitfall traps. Considering our records of N. ferreirai and the ecoregions associated with them, we argue that the species range may extends north along the interfluves Xingu-Tocantins and Madeira-Tapajos and west to the Guapore River. Similarly, the limits of the range of N. oyapocki may coincide with the Amazon river at south, the Negro river at west and the transition zones between the Guianan forests and savannas or coastal vegetation at east and north. Larger series of Neusticomys in collections are expected to be available in the future, as more inventories using pitfall traps are carried out in Amazonia.