First Amphilestid from South America: A Molariform from the Jurassic Cañadón Asfalto Formation, Patagonia, Argentina

Abstract

We report here the first amphilestid triconodont from the Jurassic of South America. The specimen, a single isolated molariform, was found at the Queso Rallado locality from where a growing mammalian fauna is known (including a triconodontid, two australosphenidans, and an as yet undescribed allotherian). The specimen, interpreted as a left lower tooth, presents five mesiodistally aligned, fairly symmetrical cusps, and is recognized as the type of a new taxon, Condorodon spanios. The phylogenetic analysis recovers Condorodon as a member of the clade Amphilestheria, closely related to Tendagurodon janenschi, an amphilestid triconodont from the Late Jurassic of Tanzania. Condorodon spanios is only distantly related to Argentoconodon fariasorum, the other triconodont known from Queso Rallado quarry. The phylogenetic position of Condorodon spanios points to the origin and diversification of amphilestherians during the Early Jurassic in a paleogeographical setting that allowed wide dispersion of these forms and argues, at least from the mammalian evidence, against a highly provincialized Pangaea. Some differences are however established between the filial western/eastern Gondwanan masses and their respective faunas.