Electronic Theses and Dissertations (Masters)

Permanent URI for this collectionhttps://hdl.handle.net/10539/38012

Browse

Filters

2023 - 20242

Settings

Start date: 2023Subject: search.filters.subject.Palaeontology

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Finite Element Analysis of Dinocephalian Skulls to Address Head-Butting Behaviour in Early Therapsids
    (University of the Witwatersrand, Johannesburg, 2024-08) Bolton, Andrew; Benoit, Julien; Mangera, Taahirah
    The origin of complex social behaviour in the mammalian lineage has been a long-standing enigma. Behaviours do not leave a rich fossil record; however, adaptations to highly specialised complex behaviour can be traced back in some lineages, such as the dinocephalians. Dinocephalians dominated carnivorous and herbivorous niches of terrestrial ecosystems in the Middle Permian (~273-259 million years ago). Species within this clade often have skulls with considerable pachyostosis (overly thickened bones) and cranial ornamentation (horns and bosses). This morphology has been interpreted as evidence for head-butting, but the evidence is circumstantial at best. For this project, I used three-dimensional models of the skulls of four dinocephalians and two outgroups to simulate and investigate the capabilities of these skulls to withstand different magnitudes of head-butting and flank-butting impacts with finite element analyses. Palaeopathological analyses vindicated the accuracy of FEA data, which indicates that dinocephalian skulls modelled here arguably reflect biological truth. As head-butting is a complex social behaviour, this would strongly suggest the presence of dominance hierarchies, territoriality, and gregariousness. This represents the earliest robust evidence of complex social behaviour in tetrapods, preceding all known examples of social interactions in dinosaurs and mammals by hundreds of millions of years.
  • Thumbnail Image
    Item
    Cranial orientation and the lateral semicircular canal in primates: implications for palaeobiological reconstructions and the evolution of locomotor repertoires
    (University of the Witwatersrand, Johannesburg, 2023) Pestana, Christopher; Benoit, Julien; Beaudet, Amélie
    The lateral semicircular canal and its predicted relation to head posture have been used in reconstructions of locomotion and posture of contemporary and extinct species, and in the evolution of bipedalism. Inferences of head posture in fossil species sometimes assume that the lateral semicircular canal is held near the earth’s horizontal when the head is at rest. Despite the physiological importance of the vestibular system, the relationship between head posture and lateral semicircular canal orientation in primates has not been explored on a statistically significant sample, using phylogenetically corrected methods. This study tests the hypothesised relationship between lateral semicircular canal orientation and head posture in primates, and investigates potential links to locomotor categories. This study finds that lateral canal orientation is not significantly correlated to positional repertoires. Significant differences in canal orientation are detected between terrestrial and arboreal species. Neutral head posture distinguishes several locomotor categories, and explains a moderate proportion of the variance in positional behaviour. Brain mass is found to correlate with positional behaviour when correcting for the effects of the phylogeny. The implications of the evolution of head posture in fossil species are discussed.