Disparity, evolution, and convergence among felid and felid-like carnivorans

Felidae stands out as one of the most successful families of carnivorans in modern ecosystems, with a global presence on every continent except Antarctica. These hypercarnivores are typically regarded as apex predators but display a wide range of sizes: from the diminutive Indian forest-dwelling rusty-spotted cat Prionailurus rubiginosus (0.9 to 1.6 kg) to the formidable Siberian tiger, Panthera tigris altaica (100 to 306 kg).
Felids were, however, much more disparate in the past, notably thanks to fossil species exhibiting elongated and laterally flattened upper canines; these sabertoothed cats are known as the subfamily Machairodontinae. The evolution of saber teeth occurred multiple times in the fossil record, notably in another carnivoran family: Nimravidae. Interestingly, some machairodontine felids (tribe Metailurini) and some nimravids (tribe Nimravini) later exhibit forms with shorter upper canines, bearing striking resemblances to modern-day cats. While the systematics and functional anatomy of cat-like carnivorans have been extensively studied in recent decades, our understanding of their disparity, adaptive landscape, and evolutionary trajectories over time remains incomplete.
Previous research often focused on single clades without a comprehensive phylogenetic framework. Hence, the evolutionary trajectories pertaining these profound back and forth craniomandibular modifications are poorly understood. The emergence of high-precision 3D surface scanning and high-density geometric morphometrics offers a promising avenue to address these knowledge gaps, particularly when used to generate a large and phylogenetically robust dataset. The objectives of this Ph.D. project were, therefore, to assess the disparity of cat-like carnivorans through time and space, compare the evolution of their craniomandibular shape and biomechanics, provide evidence of convergent evolution within these clades, and study processes driving the development of a cat-like phenotype.
I constructed the most extensive dataset of cat-like crania and mandibles ever assembled, exploring two primary aspects: shape (quantified through 3D geometric morphometrics) and function (assessed via finite element analysis). Both shape and function analyses revealed a continuum of cat-like adaptations, even within the saber-toothed morphotype. No clear distinctions among clades, tribes, or morphotypes were discernible, suggesting a wide spectrum of hunting methods. Some derived sabertoothed felids still exhibit lower stress values simulated biting at wide gape angles and when executing anchor bites, even during juvenile stages. This implies the presence of anchoring or high-gape adaptations in the mandibles in the most derived taxa. The study also unveiled distinct ontogenetic trajectories, a higher rate of morphological changes during growth, accelerated rates of morphological evolution, and entirely different patterns of morphological integration within the craniomandibular complex of clades containing saber-toothed taxa. These findings suggest that these factors might be instrumental in the development of saber teeth. Although the last saber-toothed taxa vanished relatively recently, cat-like carnivorans have experienced a decline in disparity since their radiation in the Miocene.