A new species of Oxymycterus (Rodentia: Cricetidae: Sigmodontinae) from the Yungas of Argentina.

Abstract

Morphological and molecular studies allowed us to recognize a new species of Oxymycterus from the southern end of the Yungas of Argentina. External morphologic traits allow the new species, Oxymycterus wayku, to be differentiated from O. paramensis and O. akodontius, the two currently recognized species for northwestern Argentina, as well as from the remaining species of the genus. Those traits include very dark general coloration, ears covered with nearly black hairs, a white spot on the chin, and claws on fore and hind feet long and robust. Cranial characteristics of the new species include wide and relatively shallow zygomatic notches, proportionally short incisive foramina and molar series, and a relatively robust braincase compared to O. paramensis. Phylogenetic analysis based on cytochrome b DNA sequences corroborates the distinctiveness of Oxymycterus wayku n. sp. Observed divergence values support this distinction. This new species is particularly important from a conservation viewpoint due to its rarity and the advanced level of alteration of its habitat.