“XYOPHORUS” SP. EN EL MIOCENO MEDIO DE CHUBUT: IMPLICANCIAS SISTEMÁTICAS, BIOGEOGRÁFICAS Y BIOCRONOLÓGICAS DEL REGISTRO DE UN NOTHROTHERIINAE EN EL NEÓGENO DE LA ARGENTINA

Abstract

“XYOPHORUS” SP. FROM THE MIDDLE MIOCENE OF CHUBUT PROVINCE: SYSTEMATIC, BIOGEOGRAPHIC, AND BIOCHRONOLOGIC IMPLICATIONS OF THE RECORD OF A NOTHROTHERIINAE FROM THE NEOGENE OF ARGENTINA. Xyophorus Ameghino was described based on mandibular fragments of Xyophorus rostratus Ameghino from the Early Miocene of Patagonia. The specimen herein described was collected in the locality “El Petiso”, located in northwestern Chubut Province, in sediments referred to the Middle Miocene and it is represented by a mandibular fragment that is characterized by: (1) posterior margin of the mandibular symphysis anterior to the plane of the caniniform; (2) posterolateral opening of mandibular canal on the lateral side of the coronoid process and nearly to the oclusal plane; (3) oclusal surface of the m1–m3 with two crests separated by a “V” valley; and (4) m1–m2 presents vertical grooves on the labial and lingual sides, and m3 with a groove on the labial one. The features present in this specimen and in the species herein referred to “Xyophorus” bondesioi Scillato-Yané, and “Xyophorus” villarroeli Saint-André allow distinguishing them from the species of the genus Xyophorus (e.g., X. andinus Ameghino, X. atlanticus Ameghino, X. crassissimus Ameghino) justifying the erection of a new genus and its inclusion in Nothrotheriinae. The record of “Xyophorus” sp. from the Middle Miocene of Chubut Province represents the oldest and australmost for Nothrotheriinae from Argentina, whereas, the record of “Xyophorus” cf. bondesioi from the locality of Cerdas, in Bolivia, would correspond to the oldest one for the subfamily.