Electronic Theses and Dissertations (Masters)

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

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Start date: 2023Subject: search.filters.subject.SDG-4: Quality education

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    Taphonomy and palaeoecology of a monospecific microvertebrate bonebed: behavioural implications for the late Permian (Lopingian) parareptiles
    (University of the Witwatersrand, Johannesburg, 2024-06) Mukwevho, Lutendo; Choiniere, Jonah; Smith, Roger
    Sociality in the vertebrate fossil record is a dynamic and fast-expanding area of research. Natural history observations of living animals are crucial for understanding and categorizing sociality, but these observations are not feasible for extinct species. Monotaxic bonebeds provide unique opportunities to conceptualize the social behaviours of these extinct animals. An unusual bonebed (SAM-PK-K11289) discovered in the uppermost Permian strata of the Balfour Formation, Karoo Supergroup, in the Eastern Cape presents a window into the sociality of Late Permian reptiles. The use of propagation phase-contrast synchrotron X-ray microcomputed tomography permitted the 3D reconstruction of skeletal elements in SAMPK-K11289, allowing the taxonomic identification of the individuals in the bonebed as most likely belonging to Owenetta. This is the largest aggregation of Owenetta individuals known to date, with a minimum number of 31, which are all very similar in body size. The ontogenetic profile of SAM-PK-K11289 was interpreted by analysing the size distribution of duplicate elements and by making comparisons with other Owenetta and procolophonid specimens. The specimens in the bonebed are all osteologically immature, indicating that they are juveniles. The bonebed occurs in a pedogenically modified ripple cross-laminated siltstone suggesting that a low-energy fluvial sedimentation likely contributed to the modification, disturbance and disarticulation of elements before the bonebed was buried at or very close to the death site. This bonebed provides novel information that directly challenges the popular belief that reptiles and their ancestors are non-social or asocial. Considering the overall circumstances of the bonebed, I hypothesize that Owenetta rubidgei juveniles were socially gregarious and this behaviour may have been induced or influenced by environmental changes during the early extinction phase of the end Permian mass extinction in the Karoo Basin.
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    The Taxonomy and Phylogeny of Varanopidae from the Middle Permian of outh Africa
    (University of the Witwatersrand, Johannesburg, 2024-08) Sibiya, Zoleka; Rubidge, Bruce; Benoit, Julien
    Varanopidae are the only pelycosaur-grade tetrapods from the Abrahamskraal Formation of the Beaufort Group. Although four varanopid species are described from the middle Permian of South Africa (SA), their validity has been questionable. Moreover, Ford and Benson recently proposed that varanopids belong to the Diapsida rather than Synapsida. Given this taxonomic and phylogenetic turmoil, this study i) describes two newly discovered and well-preserved varanopid specimens from the middle Permian of SA using CT scanning and ii) re-assesses the validity of the four species from the Karoo Basin in the light of new data from these specimens. The phylogeny of the group is addressed by updating two pre-existing cladistics matrices. The two new specimens exhibit a mosaic of features that overlap the diagnoses of several species of SA varanopids. In addition, some diagnostic traits of the four SA varanopid genera and species are found to be variable across ontogeny. For instance, dorsal osteoderms and the extent of ornamentation on the angular bone co-vary with size. It is therefore proposed that all varanopid specimens currently described from the middle Permian of South Africa belong to a single valid species, Heleosaurus scholtzi, with differences between specimens being accounted for by ontogenetic changes. The phylogenetic analysis supports Ford and Benson’s hypothesis but contra the prediction of this hypothesis, no differences in cranial fenestration during ontogeny are observed. Morphological characters preserved in the manus of the newly discovered specimen BP/1/8499 suggest that Heleosaurus was arboreal.
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    Palaeoclimate Reconstruction Using Charcoal from a Mid-Holocene Stratum 4b, Wonderwerk Cave, South Africa
    (University of the Witwatersrand, Johannesburg, 2024-06-18) Hlophe, Busisiwe; Bamford, Marion
    Caves are often sources for palaeoenvironmental information in the dry interior regions of southern Africa. The Wonderwerk Cave, located in Northern Cape, is a national heritage site with a well-preserved, nearly complete record of the local Holocene LSA techno-complexes and past environmental indicators. Hence, it has the potential to provide valuable insights into past human behaviour as well as the local palaeoclimate and vegetation. This study examined wood charcoal from stratum 4b, Excavation 1 of the Wonderwerk Cave. The aim was to evaluate the taxonomic composition and the physiognomy of the charcoal to understand the environment around the cave 6.9-5.9 ka. The study also investigated the modern uses of the vegetation to infer how humans may have utilized the woody plants around them during that period. The results indicate the landscape cover included woody plants adapted to dry conditions and summer rainfall. However, the archaeological taxa identified also included two species that thrive in moist environments, Halleria lucida and Olinia ventosa, suggesting fluctuations in climate. The taxonomic composition also suggests an environment similar to the modern bushveld found near the cave. The low conductivity capacity as well as vulnerability and mesomorphy indices of the woods support the implication that the vegetation was adapted to low water availability or aridity. The cave's inhabitants likely used the identified plants for firewood, magical and medicinal purposes, and more between 6.9 and 5.9 ka.
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    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.