Le jeudi 5 octobre 2023, Narimane CHATAR 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.

Cette épreuve consistera en la défense publique d’une dissertation intitulée :

« Disparity, evolution, and convergence among felid and felid-like carnivorans ».

Abstract

This PhD thesis focuses on the disparity, evolution and convergence among two groups of cat-like carnivorans: Felidae and Nimravidae which both developed impressive saber teeth. Despite extensive research on cat-like carnivorans, our understanding of their diversity, adaptation, and evolutionary pathways remains incomplete, often limited to individual clades or the most derived taxa. Leveraging high-precision 3D surface scanning, biomechanical simulations and geometric morphometrics, this PhD project aimed to assess the temporal and spatial disparity of cat-like carnivorans, analyze their cranio-mandibular evolution and functioning, quantify the phenomenon of convergence, and explore the processes shaping their feline phenotype. The study compiled the most extensive dataset of cat-like cranial and mandibular specimens to date, demonstrating a continuum of adaptations, even among saber-toothed forms. The research highlighted a lack of clear distinctions between clades, suggesting a broad range of hunting strategies. Still, some highly derived saber-toothed felids exhibited unique adaptations in their mandibles, already seen at juvenile stages, implying the presence of anchoring or wide-gape mechanisms at early stages of the development. Additionally, the study identified distinct ontogenetic trajectories, increased morphological changes during growth, accelerated evolutionary rates, and unique patterns of cranio-mandibular integration in clades with saber-toothed taxa. These findings provide insight into the development of saber teeth. Finally, cat-like carnivorans have seen a decline in disparity since their radiation in the Miocene, showing that this morphotype was on the brink of collapse long before their complete extinction.

Le Jury sera composé de :

M. B. CHARLIER (Président), Mme et MM. A.C. FABRE (Naturhistorisches Museum Bern), V. FISCHER (Promoteur), J. MACLAREN (Secrétaire), C. MELORO (Liverpool John Moores University), Z.J. TSENG (University of California).