The 'swamp monster' of the Tremembé Formation (Taubaté Basin, Brazil; late Oligocene): a description of a carnivorous metatherian (Sparassodonta, Proborhyaenidae)

Sparassodonta is an extinct clade of South American metatherians that occupied the role of carnivorous predators on the continent during the Cenozoic Era. The Oligocene was a significant period for the diversification of several mammalian lineages, being the time when the largest sparassodonts, such as several Proborhyaenidae evolved. Among the known localities with fauna from this epoch, the Taubaté Basin (late Oligocene, Deseadan SALMA), located in the State of São Paulo, southeastern Brazil, is the only one from Brazil dated to this period. The fauna from this locality is represented by Metatheria, Chiroptera, Rodentia, Cingulata, Astrapotheria, Litopterna, Notoungulata, and Pyrotheria. Here, we describe specimen MHNT.VT.2075, a lower canine of a large sparassodont from this fauna. This canine is assigned to the Proborhyaenidae based on the presence of an open root and labial and lingual midline sulci. This record increases the diversity of large mammals in this locality. Overall, the Tremembé Formation is a significant geological and paleontological resource that provides valuable insights into the final stages of the Paleogene period in intertropical South America. Keywords: Paleogene, sulci, procumbence, canine, phylogenetic analysis.