Le jeudi 23 mars 2023, Rebecca BENNION présentera l'examen en vue de l’obtention du grade académique de Docteur en Sciences (Collège de doctorat en Géologie) sous la direction de Valentin FISCHER et Olivier LAMBERT.
Cette épreuve consistera en la défense publique d’une dissertation intitulée :
« Convergence in cranial evolution in tail-propelled raptorial marine tetrapods ».
Ever since they first made the transition to life on land around 350 million years ago, approximately 60 lineages of tetrapods have reinvaded aquatic ecosystems. The constraints that arose from living in water rather than air have forced the evolution of similar morphologies within these groups, making them textbook examples of convergence and ideal independent replicates to questions of the influence of evolutionary constraints and the importance of historical contingency. Secondarily aquatic tetrapods have colonized many ecological niches ranging from small piscivores to gigantic megapredators, however the ecological convergences and the macroevolutionary pathways behind these are poorly understood and lack a quantitative framework.
This thesis investigates cranial ecomorphological convergence in three major nonoverlapping radiations of marine amniotes: two reptilian clades (ichthyosaurians and mosasaurids), and one mammalian (toothed cetaceans, including basilosaurid archaeocetes, toothed mysticetes, and odontocetes). These three clades all share a raptorial, pelagic lifestyle with tail-propelled locomotion. Using detailed anatomical observations, scanning electron microscopy (SEM), and a large dataset of three dimensional (3D) models of well-preserved skulls and mandibles, a range of analyses were carried out to investigate ecomorphological evolution through time, including functional ratios and 2D geometric morphometrics. Overall, my results show that marine tetrapods do not evolve exact convergence on the same roles through time, but rather show a range of equally effective solutions to the ecological problems of aquatic life.
Le Jury sera composé de :
M. B. CHARLIER (Président), MM V. FISCHER (Promoteur), E. FITZGERALD (Museum Victoria, Melbourne), O. LAMBERT (Co-promoteur), E. PARMENTIER (Secrétaire), T. SCHEYER (Universität Zürich).
La thèse est intitulée : « Scents of the past - investigating non-destructive prehistoric adhesive identification via dynamic headspace - multidimensional gas chromatography ».
La thèse est intitulée : « Novel Flow Processes toward Water Soluble CdX QDs ».
La thèse est intitulée : « Natural variation in the zinc deficiency responses among accessions of the grass model Brachypodium distachyon ».
