A large mammalian predator (Metatheria, Sparassodonta, Proborhyaenidae) in the Guabirotuba Formation (Curitiba Basin; middle Eocene)

Abstract

Proborhyaenidae are the largest known sparassodonts, with a fossil record spanning from the early Eocene to the Pliocene. The Eocene record of this group is scarce, occurring only in four geological units: Las Violetas Formation, lower Lumbrera Formation, Sarmiento Formation and Geste Formation, all in Argentina. Herein, a new occurrence of this clade is described from the Guabirotuba Formation (late middle Eocene) of the Curitiba Basin in Brazil. This unit, along with the Itaboraí and Taubaté basins are the only units in Brazil with Paleogene continental mammal records. The specimen MCN.P.1340 is an isolated lower left canine, that displays the main features associated with the lower canines of proborhyaenids, such as, an open root, median sulci, a thin enamel layer and posterior curvature. This new occurrence not only represents the biggest mammalian predator of the Guabirotuba Fauna, an expansion of the known geographical range of the family, but also provides further support for the relative dating of the Guabirotuba Formation and its fauna.