A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2013 / A thorough description and cladistic analysis of the Antetonitrus ingenipes type material sheds further light on the stepwise acquisition of sauropodan traits just prior to the Triassic/Jurassic boundary. Although the forelimb of Antetonitrus and other closely related sauropododomorph taxa retains the plesiomorphic morphology typical of a mobile grasping structure, the changes in the weight-bearing dynamics of both the musculature and the architecture of the hindlimb document the progressive shift towards a sauropodan form of graviportal locomotion. Nonetheless, the presence of hypertrophied muscle attachment sites in Antetonitrus suggests the retention of an intermediary form of facultative bipedality. The term Sauropodiformes is adopted here and given a novel definition intended to capture those transitional sauropodomorph taxa occupying a contiguous position on the pectinate line towards Sauropoda. The early record of sauropod diversification and evolution is re-examined in light of the paraphyletic consensus that has emerged regarding the ‘Prosauropoda’ in recent years.

This thesis is centred around an anatomical study of the cranial osteology of the Mesozoic sphenodontidans, Asiacephalosaurus wangi, Rarojugalosaurus mcgilli, Dianosaurus petilus and Homoeosaurus maximiliani. The first two are newly discovered and have not been studied previously. The third, previously described only in a preliminary fashion, was misinterpreted as a protorosaur. Although many specimens of H. maximiliani have been described (Cocude-Michel, 1963; Faber, 1981) since the species was first named by Meyer (1845), the newly exposed dorsal part of the skull of a new specimen has provided many new cranial features. Consequently, it was necessary to examine, draw and describe all of these sphenodontidans. The descriptions are all original and present a virtually complete picture of the cranial osteology of these genera for the first time. In addition, the different patterns of the middle ear apparatus of the Sphenodontida and the functional problems of the temporal region in the Lepidosauria have been considered. Although use is made of the literature to obtain background data, the conclusions drawn are original unless explicitly stated otherwise. Finally, the detailed descriptions of the four genera have permitted a reassessment of the phylogeny of the Sphenodontida. After reviewing the literature, original conclusions are given.

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