A New Species of Incanomys (Rodentia: Cricetidae: Sigmodontinae) from the Yungas of Peru

Recent systematic studies of ichthyomyine rodents have notably improved our knowledge about the evolution of the group but indicated that additional taxonomic work is still needed within the tribe. Here, we describe Incanomys parviauris, sp. nov., based on molecular and morphological evidence obtained from specimens collected in the north-central Yungas of Peru. Our phylogenetic analyses of mitochondrial and nuclear gene sequence data recovered I. parviauris as sister species of the recently described genus and species I. mayopuma. The K2P-corrected genetic distance between I. parviauris and I. mayopuma is about 10% at the cytochrome b locus. Additionally, I. parviauris differs from I. mayopuma by a unique set of morphological features, including the ventral fur slightly contrasting with the dorsal fur, four plantar pads on the manus (hypothenar fused with the third interdigital), posterior border of the incisive foramina anterior to M1, and occipital condyles visible in dorsal view of the skull. Furthermore, the presence of only two pairs of mammae in the adult female holotype of I. parviauris appears unique in the tribe. Incanomys parviauris is only the second known species of the genus, and it is the only ichthyomyine species currently known from high elevations in the eastern Andes between the Marañón and Huallaga rivers, an area to which it might be endemic.