Braincase and endocranium of the Placodont Parahenodus atancensis de Miguel Chaves, Ortega & Pérez-García, 2018, a representative of the highly specialized clade Henodontidae

Abstract

Parahenodus atancensis de Miguel Chaves, Ortega & Pérez-García, 2018 is a recently described bizarre cyamodontoid placodont, based on a partial but well-preserved Spanish Upper Triassic skull. It was identified as the sister taxon of the German highly specialized Henodus chelyops Huene, 1936. The use of micro-computed tomography has been able to significantly increase knowledge of the cranial anatomy of Parahenodus atancensis by the characterization of several bones and structures previously unknown for this taxon, as well as to obtain a partial reconstruction of its brain endocast and associated endocranial structures, poorly known in most Triassic sauropterygians. In addition, we identify several synapomorphies of the braincase of Cyamodontoidea so far unknown in Henodontidae, improving knowledge about this clade. The study of the endocranium and neurosensory structures of Parahenodus atancensis suggests a relatively lower reliance on vision, the pineal system and the pituitary than in other Triassic sauropterygians.