Palaeontologia africana

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ISSN (print): 0078-8554 ISSN (electronic): 2410-4418 For queries regarding content of Palaeontologia africana collections please contact Jonah Choiniere by email : jonah.choiniere@wits.ac.za or Tel : 011 717 6684

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Author: search.filters.author.Smith, Roger M. H.Has files: Yes

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    Re-discovery of the Euparkeria bonebed locality (Mid-Triassic) in Aliwal North, South Africa, with an update of the taphonomy and depositional environment
    (2023-07) Wolvaardt, Frederik P.; Smith, Roger M. H.; Arcucci, Andrea
    Euparkeria capensis is an Early to Middle Triassic archosauriform reptile widely regarded as phylogenetically close to the base of the Archosauria. Fossils of this species are only known from a single locality in the townlands of Aliwal North, South Africa. The exact location was, until now, uncertain due to mis-reading of the field notes of the collector Mr Alfred ‘Gogga’ Brown and conflicting anecdotal information gleaned from local townsfolk. Careful transcription of the voluminous handwritten field notes, followed by archival research in the town museum, and ground-truthing of the targeted area, has led to the re-discovery of the Euparkeria type locality. Sedimentological facies analysis of the locality combined with taphonomic observations of the 38 fossil-bearing rock slabs collected by Brown, now housed in the Iziko South African Museum reveal the following scenario for the origin of the Euparkeria/ Mesosuchus bonebed: the bones are preserved within the base of two tabular massive sandstone beds in upper point-bar facies of a high sinuosity channel-fill. The stratigraphic position, sedimentology, and geometry of the sandstone beds with their interdigitation with overlying floodplain mudrocks is interpreted as part of an infilled chute-channel cutting across a point-bar of a meandering river. The taphonomic analysis of the main bonebed suggests that the initial concentration of tetrapod remains was controlled by a combination of a mass mortality event of a pack of Euparkeria, and a few Mesosuchus becoming overwhelmed by a flash flood, and the hydrodynamics of the small floating carcasses getting trapped within the confines of a downstream chute-channel. The re-discovered Euparkeria locality is stratigraphically positioned at the top of a locally significant sandstone marker bed informally named the Eldorado marker. This unit is generally accepted as the contact between the lower and middle Burgersdorp Fm. Biostratigraphically, the locality is positioned within the transition between the lower and middle subzones of the Cynognathus AZ, namely Langbergia-Garjainia below and Trirachodon- Kannemeyeria above. This is some 23mlower in the stratigraphy than previously thought, and the possible association with Langbergiatype burrow casts leads us to tentatively place it within the lower subzone.
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    The mandible of Compsodon helmoedi (Therapsida: Anomodontia), with new records from the Ruhuhu Basin, Tanzania
    (2023-07) Angielczyk, Kenneth D.; Peecook, Brandon R.; Smith, Roger M. H.
    The emydopoid dicynodont Compsodon helmoedi originally was named from a single skull collected in Daptocephalus Assemblage Zone strata in the South African Karoo Basin. Recently described specimens from the Luangwa Basin, Zambia, have elucidated the species’ cranial morphology and facilitated identification of other historical Karoo specimens. Neither the holotype nor any of the described Zambian specimens preserve a mandible; a referred Karoo specimen preserves a highly damaged mandible, but poor preservation obscures most details.We present an additional Zambian Compsodon specimen that includes an articulated cranium and mandible, and use μCT data to describe the mandible of this taxon for the first time. The mandible has an upturned dentary symphysis; ‘postcanine’ teeth with coarse distal denticles; a shallow, elongate posterior dentary sulcus with medial expansion anterior to the tooth row, and a prominent lateral dentary shelf. Although the mandible is similar to those of Emydops and Pristerodon, it can be differentiated from Emydops by the latter’s more triangular posterior dentary sulcus, and the absence of a rugose muscle scar on the lateral edge of the lateral dentary shelf. It differs from Pristerodon in the absence of a dentary table rostral to the tooth row, the presence of a transverse ridge dividing the lateral dentary shelf into posterior and anterior sections, and the anterodorsal angulation of the lateral dentary shelf. Three fragmentary specimens from the Usili Formation (Ruhuhu Basin) display the same morphotype and represent the first record of Compsodon from Tanzania. The expanding geographic range of Compsodon underscores its potential as a biostratigraphic index fossil, but more information on its stratigraphic and temporal ranges is needed to realize that potential.
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    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.
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    An aggregation of juvenile Youngina from the Beaufort Group, Karoo Basin, South Africa
    (Bernard Price Institute for Palaeontological Research, 1995) Smith, Roger M. H.; Susan, E. Evans
    An assemblage of five fully-articulated juvenile skeletons of Youngina has been recovered from the Late Permian strata of the south-western Karoo Basin. These 12-cm-long skeletons are not only the first articulated juveniles of this taxon, but also the oldest yet found in the Karoo Basin. They are preserved in overbank mudrocks of the Hoedemaker Member (Beaufort Group, Adelaide Subgroup) on the farm Leeukloof 43 in the Beaufort West district. Although they are estimated to be some three million years older than previously described Youngina, these specimens show no significant skeletal differences. The high degree of articulation and the spatial arrangement of these skeletons in a dish-shaped hollow is compelling evidence for them having huddled together within an underground burrow. Taphonomic analysis of associated fossils indicates that this was probably a mechanism to reduce water loss during drought on the ancient Karoo floodplains .
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    On the stratigraphic range of the dicynodont taxon Emydops (Therapsida: Anomodontia) in the Karoo Basin, South Africa
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 2005) Angielczyk, Kenneth D.; Fröbisch, Jörg; Smith, Roger M. H.
    The dicynodont specimen SAM-PK-708 has been referred to the genera Pristerodon and Emydops by various authors, and was used to argue that the first appearance of Emydops was in the Tapinocephalus Assemblage Zone in the Karoo Basin of South Africa. However, the specimen never has been described in detail, and most discussions of its taxonomic affinities were based on limited data. Here we redescribe the specimen and compare it to several small dicynodont taxa from the Tapinocephalus and Pristerognathus assemblage zones. Although the specimen is poorly preserved, it possesses a unique combination of features that allows it to be assigned confidently to Emydops. The locality data associated with SAM-PK-708 are vague, but they allow the provenance of the specimen to be narrowed down to a relatively limited area southwest of the town of Beaufort West. Strata from the upper Tapinocephalus Assemblage Zone and the Pristerognathus Assemblage Zone crop out in this area, but we cannot state with certainty from which of these biostratigraphic divisions the specimen was collected. Nevertheless, SAM-PK-708 is an important datum because it demonstrates that the stratigraphic range of Emydops must be extended below its widely-accepted first appearance in the Tropidostoma Assemblage Zone. This range extension is significant because it implies that the divergence between the emydopid and dicynodontid lineages must have occurred no later than Pristerognathus Assemblage Zone times, and that most of the major lineages of Permian dicynodonts had emerged by a relatively early point in the history of the group.