Virtual endocasts of Clevosaurus brasiliensis and the tuatara: Rhynchocephalian neuroanatomy and the oldest endocranial record for Lepidosauria

Autor(es)

Roese-Miron, Livia ; Jones, Marc Emyr Huw ; Ferreira, Jose Darival ; Hsiou, Annie Schmaltz

• Tipo de documento: Artigo Científico
• Fonte: Anatomical Record-Advances in Integrative Anatomy and Evolutionary Biology; v. N/A, p. 24-pg., 2023-03-23.

Resumo

Understanding the origins of the vertebrate brain is fundamental for uncovering evolutionary patterns in neuroanatomy. Regarding extinct species, the anatomy of the brain and other soft tissues housed in endocranial spaces can be approximated by casts of these cavities (endocasts). The neuroanatomical knowledge of Rhynchocephalia, a reptilian clade exceptionally diverse in the early Mesozoic, is restricted to the brain of its only living relative, Sphenodon punctatus, and unknown for fossil species. Here, we describe the endocast and the reptilian encephalization quotient (REQ) of the Triassic rhynchocephalian Clevosaurus brasiliensis and compare it with an ontogenetic series of S. punctatus. To better understand the informative potential of endocasts in Rhynchocephalia, we also examine the brain-endocast relationship in S. punctatus. We found that the brain occupies 30% of its cavity, but the latter recovers the general shape and length of the brain. The REQ of C. brasiliensis (0.27) is much lower than S. punctatus (0.84-1.16), with the tuatara being close to the mean for non-avian reptiles. The endocast of S. punctatus is dorsoventrally flexed and becomes more elongated throughout ontogeny. The endocast of C. brasiliensis is mostly unflexed and tubular, possibly representing a more plesiomorphic anatomy in relation to S. punctatus. Given the small size of C. brasiliensis, the main differences may result from allometric and heterochronic phenomena, consistent with suggestions that S. punctatus shows peramorphic anatomy compared to Mesozoic rhynchocephalians. Our results highlight a previously undocumented anatomical diversity among rhynchocephalians and provide a framework for future neuroanatomical comparisons among lepidosaurs. (AU)

• Processo FAPESP: 20/06819-5 - Novos materiais de Clevosaurus (Rhynchocephalia, Sphenodontia) do Triássico do Brasil: abordagens acerca da variação ontogenética e anatomia endocraniana
• Beneficiário: Lívia Roese Miron
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 19/14153-0 - A fauna de pequenos vertebrados do Neógeno da Amazônia Brasileira, com ênfase na resolução temporal da Formação Solimões, Mioceno da Bacia do Acre
• Beneficiário: Annie Schmaltz Hsiou
• Modalidade de apoio: Auxílio à Pesquisa - Regular