A new, nearly complete skull of Procolophon trigoniceps Owen, 1876 from the Sanga do Cabral Supersequence, Lower Triassic of Southern Brazil, with phylogenetic remarks

Abstract

ABSTRACTThe Sanga do Cabral Supersequence comprises the Sanga do Cabral and the Buena Vista formations from Brazil and Uruguay respectivelly. The Brazilian unit yields an abundant record of the procolophonid Procolophon trigoniceps, a biostratigraphic marker for the Lower Triassic, which allows correlation with the Katberg Formation, South Africa. P. trigoniceps, has a wide territorial extension, so this is one of the most successful groups after the greatest extinction event, the Permo-Triassic Extinction. We describe a new skull ascribed to Procolophon trigoniceps, which so far represents the most complete and best preserved specimen collected at the Lower Triassic Sanga do Cabral Supersequence, Southern Brazil, and assess its phylogenetic relationships. We also use CT scan techniques to assess hidden structures covered by a hard layer of rock matrix as a non-invasive method, which allowed the visualization of the palatal dentition of this new specimen. The actual diversity of procolophonians at the Sanga do Cabral Supersequence is still unknown because most specimens are fragmentary and poorly preserved, so this new, nearly complete skull fills an important gap in the knowledge of South American P. trigoniceps, given that previously described specimens of this taxon from this region of Gondwana are quite incomplete in comparison.