New Data on the Clevosaurus (Sphenodontia: Clevosauridae) from the Upper Triassic of Southern Brazil

The sphenodontian fossil record in South America is well known from Mesozoic and Paleogene deposits of Argentinean Patagonia, mainly represented by opisthodontians, or taxa closely related to the modern Sphenodon. In contrast, the Brazilian fossil record is restricted to the Caturrita Formation, Late Triassic of Rio Grande do Sul, represented by several specimens of Clevosauridae, including Clevosaurus brasiliensis Bonaparte and Sues, 2006. Traditionally, Clevosauridae includes several Late Triassic to Early Jurassic taxa, such as Polysphenodon, Brachyrhinodon, and Clevosaurus, the latter well-represented by several species. The detailed description of the specimen MCN-PV 2852 allowed the first systematic revision of most Clevosaurus species. Within Clevosauridae, Polysphenodon is the most basal taxon, and an IterPCR analysis revealed Brachrhynodon as a possible Clevosaurus; C. petilus, C. wangi, and C. mcgilli as possibly distinct taxonomic entities; and the South African Clevosaurus sp. is not closely related to C. brasiliensis. These data indicate the need of a deep phylogenetic review of Clevosauridae, in order to discover synapomorphic characters among the diversity of these Triassic/Jurassic sphenodontians.