Search

Triassic rhynchocephalians from South America are relatively sparse, based on one taxon from the Norian of Argentina (i.e., Sphenotitan leyesi) and three records from the Late Carnian (i.e., indet. taxon) and Norian (i.e., Clevosaurus brasiliensis and indet. taxon) of Brazil. We described here a new occurrence of rhynchocephalians from a new Late Carnian locality of southern Brazil, based on an isolated palatine with teeth, referred to that group due to the morphological similarity whit the palatines of the other taxa of the same group. The specimen comes from the municipality of Vale do Sol, collected within a layer with abundant material of Hyperodapedon sp. (Rhynchosauria), which is referred to the Hyperodapedon Assemblage Zone (Late Carnian) of the Candelária Sequence, Santa Maria Supersequence. The isolated palatine here described cannot be referred to any hitherto known species, but it provides an additional record for the few putative ones of Carnian age in South America. Moreover, we figure and describe the palatine anatomy of Clevosaurus brasiliensis, based on two specimens, which have relevant data poorly addressed in previous contributions. [ABSTRACT FROM AUTHOR]

We describe a new eusphenodontian, Lanceirosphenodon ferigoloi gen. et sp. nov., from the Upper Triassic (Norian) Riograndia Assemblage Zone (AZ) of the Candelária Sequence (Santa Maria Supersequence) of Rio Grande do Sul, Brazil. The new taxon consists of an almost complete left dentary with dentition, which exhibits a mosaic of features considered 'typical' of non-eusphenodontian rhynchocephalians, along with others reported for eusphenodontian taxa. It has the typical rhynchocephalian regionalized dentition with 19 teeth and also pleuroacrodont implantation; the additional dentition presents alternation of size and shape, with the last additional teeth resembling a spear in labial view. A well-developed chin is also present. Our phylogenetic analysis places Lanceirosphenodon as one of the most basal eusphenodontians and reinforces the hypothesis that Rhynchocephalia underwent an early diversification, probably in the Early Triassic, followed by an explosion in morphological disparity. Based on the ontogenetic sequence of Sphenodon, Lanceirosphenodon fitted between stages T2 and T3, representing a probable early juvenile individual. In spite of its ontogenetic stage, the set of characters present in Lanceirosphenodon, including two autapomorphies, supports its recognition as a new taxon. This new taxon increases our knowledge of the faunal diversity in the Triassic of Gondwana and more locally for the Riograndia Assemblage Zone of southern Brazil. [ABSTRACT FROM AUTHOR]

Clevosaurus was a cosmopolitan rhynchocephalian genus, known from the Late Triassic to the Early Jurassic. In South America this genus is represented by C. brasiliensis, an important component of the Linha São Luiz taphocoenosis, on the top of the Norian Santa Maria 2 Sequence of Southern Brazil. The best preserved and most abundant bone elements of C. brasiliensis are dentaries, in which variations of shape and size are observed. The aim of this study is to describe and evaluate the variation, using geometric morphometrics methods. Geometric morphometric analysis of 10 specimens highlights variations in relative size of the dentary. Most of the variation observed for PC1 (83.3%) is likely related to ontogeny, and PC2 (10.0%) is likely related to taphonomic signatures. The development patterns observed, such as the growth of the dentary, consists of differential growth in length between the posterior portion of the dentary, that grows at a higher rate, regarding the anterior portion of the element. This allometric growth is similar to what is observed in other rhynchocephalians and is accompanied by the allometric skull growth, similar to the trend exhibited by clevosaurs. The taphocoenosis is bimodal (juveniles and adults) with a bias towards adult preservation. Some diagenetic influence is reflected in deformed skulls and this is observed in the tangent-plot. Finally, a strong correlation was detected between the taphonomic signatures and the PC2, regarding specially disarticulation and degree of fragmentation. [ABSTRACT FROM AUTHOR]