A New Species Of The Late Triassic Rhynchosaur Hyperodapedon From The Santa Maria Formation Of South Brazil

A new rhynchosaur, Hyperodapedon huenei sp. nov., is described from the Upper Triassic Santa Maria Formation of the Paraná Basin, Brazil. The holotype is an almost complete skull and mandible, collected at Inhamandá, in the state of Rio Grande do Sul, Brazil. The diagnosis of the genus Hyperodapedon Huxley is revised to include not only H. huxleyi Lydekker and H. gordoni Huxley (as generally accepted), but also the new species described here, various specimens usually assigned to ' Scaphonyx fischeri ' Woodward, and ' S '. sanjuanensis Sill. H. huenei sp. nov. exhibits a number of plesiomorphic features and appears to be the least derived species of Hyperodapedon , forming a sister taxon to the remaining members of the genus. A preliminary phylogenetic analysis for the more derived rhynchosaurs is presented. ' Scaphonyx ' sulcognathus Azevedo and Schultz represents the sister taxon of Hyperodapedon , while ' Rhynchosaurus ' spenceri Benton is considered to be a more derived Middle Triassic rhynchosaur. key words : Rhynchosauria, Hyperodapedon , Triassic, Brazil.