A new species of Xotodon (Notoungulata, Toxodontidae) from northwestern Argentina

Abstract

Xotodon caravela, a new species of toxodontid from northwestern Argentina, is presented. The material studied consists of a well-preserved and nearly complete mandible and a maxillary fragment, recovered in the Aconquija Formation (late Miocene-early Pliocene) at the El Molino locality (Tucumán Province, Argentina). The fossil diversity of the levels is concordant with an early Pliocene fauna. The general features of the dentition and mandible (e.g., concave ectoloph and single lingual fold on upper molars, anterior fold mesially displaced relative to the hypoflexid in the lower molars, sigmoid lateral outline of chin, and continuous enamel on M3) allow the inclusion of this specimen in the genus Xotodon. In turn, some traits indicate unequivocally that this is a new species, such as the anterior region without constriction at the premolar level, the approximately 13° angle of implantation of the i3 in relation to the ventral edge of the mandibular body (without lateral divergence), and the presence of an intra-alveolar projection of the incisive crown extending laterally below the premolars to the level of the p4 and forming a robust projection or lateral ledge. The new taxon was included in a matrix of 59 characters and compared with 32 notoungulate genera. The phylogenetic position and comparative analysis support the taxonomic interpretation of the studied specimen as a new species of Xotodon. This represents the first record of a toxodontid in the Neogene lowlands of northwestern Argentina and contributes to our knowledge of this family in the region.