La soutenance aura lieu le 19 novembre 2021, à partir de 14h, dans l'amphithéâtre de la Galerie de Paléontologie et d'Anatomie Comparée du Muséum national d'Histoire naturelle.

Mathieu Faure-Brac

Effects of thermophysiology on the evolution of Pseudosuchia (Archosauria): Contributions of paleohistology and isotopic geochemistry using phylogenetic comparative methods

Composition du jury :

  • Ana-Voica Bojar - Dozen, University of Salzburg - Rapportrice
  • Alexandra Houssaye - DR CNRS, MNHN - Rapportrice
  • Michael Benton - Professor, University of Bristol - Examinateur
  • Yves Desdevises - Professeur, Sorbonne Université - Examinateur
  • Edina Prondvai - Associated Researcher, University of Birmingham - Examinatrice
  • Loïc Ségalen - Professeur, Sorbonne Université - Examinateur
  • Jorge Cubo - Professeur, Sorbonne Université - Directeur de thèse
  • Christophe Lécuyer - Professeur, Université Claude Bernard Lyon 1 - Co-directeur de thèse
  • Romain Amiot - CR HDR CNRS, Université Claude Bernard Lyon 1 - Co-encadrant & invité

Abstract:

It is today well­established that archosaurs are ancestrally endotherms, i.e., they present mechanisms of non­shivering thermogenesis. Among archosaurs, extant crocodilians are ectothermic but present particular anatomical and molecular features traditionally associated with endothermy: a four­chambered heart; several acquisitions linked to an efficient breath such as a diaphragmatic muscle and unidirectional airflow; the deposition of high growth rate bone tissues; a high mitochondrial rate of evolution. Studies on extinct pseudosuchians suggested that most of the Triassic species were endothermic, but the timing of the loss of endothermy in Pseudosuchia still has to be constrained both temporally and phylogenetically.

In this thesis, I use stable isotopic geochemistry and quantitative osteohistology to infer the body temperature and the resting metabolic rate, to proxies to infer endothermy, of several metasuchians. I concluded that metasuchians are primitively ectothermic, and inferred the loss of endothermy at the node Crocodylomorpha using ancestral state reconstruction. I hypothesize pseudosuchian’s endothermy was in a more primitive state than dinosaurs’ and that they were not able to survive the end Triassic mass extinction. The only surviving pseudosuchians were then ectothermic crocodylomorphs, leading to extant species.

 

Published on: 20/02/2023 11:01 - Updated on: 20/02/2023 12:33

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