PhD Defense - Thomas Arbez

Phylogenetic and anatomical studies based on endocranial structures in stegocephals (ancient tetrapods)

Thèse de doctorat sous la direction de Jean-Sébastien Steyer et de Gaël Clément

Composition du jury :

• FRÖBISCH Nadia, Professeure, University von Humboldt, Berlin (Allemagne), Rapporteure
• MADDIN Hillary, Professeure, Carleton University, Carleton (Canada), Rapporteure
• FERNANDEZ Vincent, Ingénieur de Recherche, Natural History Museum, Londres (Royaume-Uni), Examinateur
• GERMAIN Damien, Maître de Conférence, Muséum national d’histoire naturelle, Paris, Examinateur
• STEYER Jean-Sébastien, Chargé de recherche, CNRS, Paris, Directeur de Thèse
• CLÉMENT Gaël, Professeur, Muséum national d’histoire naturelle, Paris, Directeur de Thèse

Abstract:

The intracranial anatomy of the stegocephals Stanocephalosaurus (Temnospondyli), Laosuchus (Chroniosuchia) and Diplocaulus (Lepospondyli) has been revealed by X-rays tomography and allowed to better understand their paleobiology: 1) the middle ear of Stanocephalosaurus would be an underwater adapted hearing system; 2) intraosseous sensorial canals have been identified in Laosuchus. The endocranial morphology have been included in a phylogenetic analysis on the debated relationships between stegocephals and lissamphibians. This analysis shows that the monophyly of Lissamphibia may result from a long-branch attraction, due to the optimisation of the cranial simplification, here as identified convergent. The morphologies of braincase, stapes and palate favour a biphyletic origin of lissamphibians among temnospondyls.