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New materials of Clevosaurus (Rhynchocephalia, Sphenodontia) from the Triassic of Southern Brazil: approaches about ontogenetic variation and endocranial anatomy

Grant number: 20/06819-5
Support type:Scholarships in Brazil - Master
Effective date (Start): October 01, 2020
Effective date (End): January 31, 2022
Field of knowledge:Biological Sciences - Zoology - Paleozoology
Principal Investigator:Annie Schmaltz Hsiou
Grantee:Lívia Roese Miron
Home Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Clevosauridae (Lepidosauria, Rhynchocephalia) was a clade of Sphenodontia considerably abundant during the early Mesozoic. Clevosaurus represents the most diverse and broadly distributed genus among the group, with species ranging from the Upper Triassic to the Lower Jurassic. In the deposits of the Upper Triassic of South America (Rio Grande do Sul, Brazil), two species of Clevosaurus are known: C. brasiliensis (Caturrita Formation, Riograndia Assemblage Zone (AZ), Norian), a small sphenodontian with several known specimens, and C. hadroprodon (Santa Maria Formation, Hyperodapedon AZ, Carnian), the oldest sphenodontian from Gondwana and the oldest in the world to present a fully acrodont dentition. With the exception of one study that investigated the ontogeny of the mandible of C. brasiliensis, the ontogenetic variation of Clevosaurus remains little known. Moreover, the endocranial anatomy of rhynchocephalians is a topic not yet investigated, and the existence of specimens of Clevosaurus that preserve the braincase allows its study. From the reevaluation of specimens from both species deposited in Brazilian paleontological collections, as well as from the description of a new specimen of C. brasiliensis and the comparison with other fossil sphenodontians from the Mesozoic, this project aims to contribute to the knowledge of the anatomy and ontogenetic variation patterns of the Clevosaurus from Southern Brazil, as well as to the understanding of its phylogenetic relationships. Also, it will be described the endocranial anatomy of C. brasiliensis and of the only living sphenodont, Sphenodon punctatus. (AU)