Volume 54: 2019–2020

Permanent URI for this collection

https://wiredspace.wits.ac.za/handle/10539/27890

Browse

Now showing 1 - 7 of 7

manual
(DURASPACE, 2005-08-17) Diol, Joe
Systematic experiments to quantitatively assess image quality for CT scans of a Karoo tetrapod fossil
(Evolutionary Studies Institute, 2019-08) Tshibalanganda, Muofhe; du Plessis, Anton; Le Roux, Stephan G.; Taylor, Wendy L.; Smith, Roger M. H.; Browning, Claire
Over the past decade non-destructive, three-dimensional visualization and analysis of fossils using X-ray tomography has greatly advanced palaeontological studies worldwide. Micro-computed tomography (microCT) is now accepted as best practice in palaeontological studies to augment the anatomical description of newly discovered fossils. Despite advances in laboratory microCT hardware, software and skills of users, there is a lack of clear methodologies for scanning and analysing fossils. Here we report on a systematic and detailed study of the quantitative effects of the variation of different microCT scanning parameters on the image quality of an unprepared fossilized Karoo tetrapod skull and parts of the postcrania. Results indicate that voltage variations do not increase the contrast for the bone as one would expect, and the best image quality solution is found using high frame averaging and high X-ray flux (current). Although this study was limited to one specimen, the results may find a practical use for future studies involving similar fossils.
Cranial morphology and phylogenetic relationship of the enigmatic dinocephalian Styracocephalus platyrhynchus from the Karoo Supergroup, South Africa
(Evolutionary Studies Institute, 2019-09) Fraser-King, Simon W.; Benoit, Julien; Day, Michael O.; Rubidge, Bruces S.
Styracocephalus platyrhynchus is an unusual dinocephalian therapsid, known only from a handful of specimens from the Tapinocephalus Assemblage Zone of South Africa. It has had a chequered taxonomic history, largely because it is characterized by cranial pachyostosis and the presence of horn-like structures that project posteriorly from the temporal region; these features are found in the clades Burnetiamorpha and Dinocephalia. Its affinities have been further obfuscated by a lack of well-preserved material. This paper presents a description of a well-preserved skull referable to Styracocephalus from the western Karoo Basin and provides a revised generic diagnosis for the genus. This study – incorporating comparative anatomy,CT scanning, and cladistic analysis – reveals new character information that was not evident from pre-existing Styracocephalus material, and incorporates this into a new phylogenetic analysis. Our analysis recovers Styracocephalidae as a well-supported, monotypic family within Tapinocephalia, which is characterized by: prominent pachyostotic nasal and supraorbital bosses; two posteriorly projecting crest-like protuberances comprising contributions by the postorbital, squamosal and tabular bones; weak lingual heels on the incisor and postcanine dentition present with a moderate upper and lower canine. As Styracocephalus is restricted to the upper part of the Tapinocephalus Assemblage Zone, it may be a useful biostratigraphic index taxon in future.
The Younger Dryas interval at Wonderkrater (South Africa) in the context of a platinum anomaly
(Evolutionary Studies Institute, 2019-10-02) Thackeray, J. Francis; Scott, Louis; Pieterse, P
Wonderkrater in the Limpopo Province in South Africa is a late Quaternary archaeological site with peat deposits extending back more than 30 000 years before the present. Palaeoclimatic indices based on multivariate analysis of pollen spectra reflect a decline in temperature identifiable with the Younger Dryas (YD). A prominent spike in platinum is documented in aWonderkrater sample (5614) with a mean date of 12 744 cal yr BP using a Bayesian model, preceding the onset of the YD cooling event. The YD platinum spike at Wonderkrater is the first to be observed in Africa in the southern hemisphere, supplementing new discoveries from Patagonia in South America, in addition to more than 25 sites with such platinum anomalies in the northern hemisphere. The observations from South Africa serve to strengthen ongoing assessments of the controversial YD Impact Hypothesis, whereby it is proposed that a meteorite or cometary impact contributed to a decline in temperature, associated inter alia with dispersion of atmospheric dust, mammalian extinctions and cultural changes.
Pleistocene vertebrate trace fossils of Robberg Nature Reserve
(Evolutionary Studies Institute, 2019-12) Helm, Charles W.; Cawthra, Hayley C.; Hattingh, Rudolph; Hattingh, Sinèad; McCrea, Richard T.; Thesen, Guy H. H.
More than 140 Late Pleistocene trace fossil sites have been identified in aeolianites and lithified foreshore deposits along a 350 kilometre stretch of the Cape south coast in South Africa. Robberg Nature Reserve lies within this area and contains a zone of concentration of such tracksites, which complement the Pleistocene vertebrate body fossil record and assist in shedding light on the palaeoenvironment and palaeoecology of the Palaeo-Agulhas Plain. Ichnofossil sites unique to or of special significance within Robberg Nature Reserve include a substantial palaeosurface exposure that allows an estimate of track density, the best-preserved rhinoceros trackway identified to date, very well preserved artiodactyl tracks in the formof natural casts, small equid tracks, large elephant transmitted tracks, and well preserved sub-surface golden mole burrows with a burrow chamber. Aeolianite layers at Robberg have recently been dated to Marine Isotope Stage (MIS) 3. Samples that we have obtained for dating from the main palaeosurface underlie these dated layers and are anticipated to contribute to the understanding of the Pleistocene geology of the Robberg Peninsula. The protected status of the area lends itself to conservation, replication, interpretation and education initiatives.
Biostratigraphic refinement of tetrapod-bearing beds from the Metangula Graben (Niassa Province, Mozambique). New radiometric dating and the first Lower Triassic tetrapod fossils from Mozambique
(Evolutionary Studies Institute, 2020-12) Aráujo, Ricardo; Macungo, Zanildo; Smith, Roger M H; Tolan, Stephen; Angielczyk, Kenneth D; Crowley, James; Milisse, Dino; Mugabe, João
Numerous fossils of the toothed dicynodont Endothiodon have been collected previously from the Permian K5 formation of the Metangula Graben (Niassa, Mozambique). However, no identifiable vertebrate fossils have been reported from other stratigraphic units in the basin. Here we report likely Triassic tetrapod remains from the base of the Fubué Formation some 700 stratigraphic metres above the dated K5 Formation. We present anatomical comparisons and a phylogenetic analysis that confirm that they have close affinities to the well-known Early Triassic dicynodont therapsid Lystrosaurus. Thus, the Metangula Graben can now join the few regions in the world that preserve terrestrial tetrapod fossils from before and after Permian-Triassic mass extinction event, giving it the potential to provide further insights into the evolution of terrestrial organisms during this major biotic crisis. We present an updated geological section and paleoenvironmental interpretations, as well as the first assessment of the vertebrate taphonomy of the K5, K6, Mount Lilonga, and Fubué Formations. We also report the first radiometric dates for the K5c member of the K5 formation. The K5c has a maximum depositional age of 258.85 ± 0.41 Ma and is thus older than previously thought, falling near the boundary between the Lycosuchus-Eunotosaurus and Tropidostoma-Gorgonops subzones of the Endothiodon Assemblage Zone, rather than being coeval with the Cistecephalus Assemblage Zone.
A new specimen of the sauropodomorph dinosaur Ignavusaurus rachelis from the Early Jurassic of Lesotho
(Evolutionary Studies Institute, 2020-12-11) Bodenham, Ewan H; Barrett, Paul M
The upper Elliot Formation (?Rhaetian–Sinemurian) of South Africa and Lesotho has yielded a rich fauna of non-avian dinosaurs, which has generally been considered to be dominated by the massopodan sauropodomorph Massospondylus carinatus. However, re-evaluation of the abundant sauropodomorph collections from this unit suggests that the species-richness of upper Elliot sites has been underestimated. Here, we describe a series of cervical and dorsal vertebrae collected from Likhoele Mountain, Lesotho, which are referred to the rare upper Elliot sauropodomorph taxon Ignavusaurus rachelis. This material represents only the second-known specimen of this taxon, extending its geographic range, and underscores the value of undertaking detailed re-assessments of neglected historical collections.

Browse

Browsing Volume 54: 2019–2020 by Issue Date

Results Per Page

Sort Options