New species of arboreal rat of the genus Rhipidomys (Cricetidae, Sigmodontinae) from Sangay National Park, Ecuador

We describe a new species of climbing rat of the genus Rhipidomys based on cranial and external morphology, morphometrics, and phylogenetic analyses of cytochrome b gene. This taxon was compared with species of Rhipidomys present in Ecuador, principally R. latimanus, which is a closely related species based on molecular analysis, and with several species from Colombia and Peru. The new species is easily distinguished from congeneric species by the relatively small size of its body (average head–body length 123 mm) and its distinctive cranial morphology including: Interorbital region constricted; postorbital crest almost imperceptible in females and evident only slightly in males; braincase wide and round; nasals narrow in their posterior and gradually expand forward; anteromedian flexus is well defined and deep; m3 with hypoflexid large and deep; mesopterygoid fossa extends beyond the third molar and capsular process on mandible well developed, forming an evident projection. The new species is only known from the southeastern portion of Sangay National Park in Ecuador and is therefore likely endemic to the Cordillera Oriental of Ecuador. We also provide natural history and reproductive observations, vocalization analysis, habitat preference, and phylogenetic placement of this species.