Dentition and feeding in Placodontia: tooth replacement in Henodus chelyops

BMC Evolutionary Biology

article

Pommery, Yannick¹  Scheyer, Torsten M.³  Neenan, James M.⁴  Reich, Tobias³  Fernandez, Vincent⁵  Voeten, Dennis F. A. E.⁵  Losko, Adrian S.⁹  Werneburg, Ingmar¹ 

[1] Senckenberg Centre for Human Evolution and Palaeoenvironment (HEP) an der Eberhard-Karls-Universität Tübingen;Université de Bourgogne-Franche-Comté;Universität Zürich, Paläontologisches Institut und Museum;Oxford University Museum of Natural History, University of Oxford;European Synchrotron Radiation Facility;The Natural History Museum;Department of Organismal Biology, Uppsala University;Naturalis Biodiversity Center;Forschungs-Neutronenquelle Heinz Maier-Leibnitz

关键词: Synchrotron tomographic scans;    Functional morphology;    Jaw mechanism;    Ontogeny;    Evolution;    Triassic;   

DOI  :  10.1186/s12862-021-01835-4

学科分类：护理学

来源: BioMed Central

【 摘 要 】

Placodontia is a Triassic sauropterygian reptile group characterized by flat and enlarged crushing teeth adapted to a durophagous diet. The enigmatic placodont Henodus chelyops has numerous autapomorphic character states, including extreme tooth count reduction to only a single pair of palatine and dentary crushing teeth. This renders the species unusual among placodonts and challenges identification of its phylogenetic position. The skulls of two Henodus chelyops specimens were visualized with synchrotron tomography to investigate the complete anatomy of their functional and replacement crushing dentition in 3D. All teeth of both specimens were segmented, measured, and statistically compared to reveal that H. chelyops teeth are much smaller than the posterior palatine teeth of other cyamodontoid placodonts with the exception of Parahenodus atancensis from the Iberian Peninsula. The replacement teeth of this species are quite similar in size and morphology to the functional teeth. As other placodonts, Henodus chelyops exhibits vertical tooth replacement. This suggests that vertical tooth replacement arose relatively early in placodont phylogeny. Analysis of dental morphology in H. chelyops revealed a concave shape of the occlusal surface and the notable absence of a central cusp. This dental morphology could have reduced dental wear and protected against failure. Hence, the concave teeth of H. chelyops appear to be adapted to process small invertebrate items, such as branchiopod crustaceans. Small gastropods were encountered in the matrix close to both studied skulls.

【 授权许可】

CC BY|CC0