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.Sidor, Christian A.

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    New and historical specimens of burnetiamorph therapsids, with comments on ontogeny, biogeography, and bizarre structures
    (2023-07) Sidor, Christian A.
    For much of its history, the fossil record of burnetiamorph therapsids was both species poor and known from very few specimens. By contrast, the past two decades have seen a dramatic increase in both measures of the group’s fossil record. Here I introduce two new species, Bondoceras bulborhynchus gen. et sp. nov. and Pembecephalus litumbaensis gen. et sp. nov., from the Guadalupian middle Madumabisa Mudstone Formation of Zambia and the Lopingian Usili Formation of Tanzania, respectively. Both are based on a series of isolated skullcaps that preserve a unique combination of characters that suggest referral to subclades within Burnetiidae. Historical burnetiamorph skullcaps collected in Tanzania in the early 1930s are figured, but these are kept in open nomenclature because not enough information is preserved to warrant assigning them to Pembecephalus or another genus. A previously undescribed Russian burnetiamorph is also figured, which is only the third specimen of the clade known from the northern hemisphere, but since the specimen is possibly lost, it is also left unnamed. Specimens referred to Bondoceras and Pembecephalus suggest that while some morphological features vary predictably with size in these burnetiamorphs, others do not, and that some features previously used to assess ontogenetic status in burnetiamorphs are sometimes similarly problematic. Despite their wide range of shapes, surprisingly little discussion of the function of burnetiamorph cranial adornments has taken place in the literature. Comparing the fossil records of burnetiamorphs and other Permian synapsids to dinosaurs with similar adornments may shed light on the macroevolutionary importance of these traits.
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    Histological evidence of trauma in tusks of southern African dicynodonts
    (Evolutionary Studies Institute, 2019-01) Whitney, Megan R.; Tse, Yuen Ting; Sidor, Christian A.
    Dicynodonts were a clade of globally-distributed therapsids known for their abundance in the fossil record and for surviving the Permo-Triassic mass extinction. The group had distinctive dental adaptations including a beak and, in many species, paired maxillary tusks. The function of these tusks has long been of interest, yet remains poorly understood.We report here on two instances of unusual morphology in tusk dentine from specimens of: 1) Lystrosaurus from the Karoo Basin of South Africa and, 2) an unidentified dicynodontoid from the Luangwa Basin of Zambia. In both, the cross-sectional shape of the tusk root is lobed and infolded, which histological features suggest is a result of abnormal dentine deposition. We infer that this abnormal morphology is likely the consequence of trauma given its reparative nature and structural similarities to trauma-related morphologies reported in the tusks of modern elephants. This study demonstrates that histological sampling of dicynodont tusks can shed light on the biology of this important clade of therapsids.
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    The vertebrate fauna of the Upper Permian of Niger — II, Preliminary description of a new pareiasaur
    (Bernard Price Institute for Palaeontological Research, 2003) Sidor, Christian A.; Blackburn, David C.; Gado, Boube
    The skull of a new pareiasaur, Bunostegos akokanensis gen. et sp. nov., is described on the basis of a partial skull from the Upper Permian Moradi Formation of north-central Niger. Autapomorphies of the genus include the presence of three hemispherical bosses at the tip of the snout, an enlarged laterally projecting supraorbital boss positioned on each postfrontal, and additional, smaller bosses on the squamosal and supratemporal bones. Bunostegos is further characterized by a tab-like process of the nasal that articulates with the frontal, a pineal foramen located equidistant between the parietal-frontal and parietal-postparietal sutural contacts, a postparietal that is excluded from the caudal margin of the dorsal skull roof, and a blunt interpterygoid vacuity. The discovery of Bunostegos suggests an unsuspected degree of biogeographic endemism for central West Africa during the Late Permian.
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    Replacement names for the therapsid genera Criocephalus Broom 1928 and Olivieria Brink 1965.
    (Bernard Price Institute for Palaeontological Research, 2002) Kammerer, Christian F.; Sidor, Christian A.
    Our knowledge of premammalian synapsid evolutionary history has benefited from over a hundred years of fossil collecting, especially within the Permo-Triassic sediments of South Africa's Beaufort Group (Rubidge 1995) and the Cis-Ural region of Eastern Europe (Ivachnenko et al. 1997). In the course of our research and discussions we have discovered several errors in the present state of non-mammalian synapsid taxonomy. Here we propose emendations concerning the genera Criocephalus Broom 1928 and Olivieria Brink 1965.
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    A new record of Procynosuchus delaharpeae (Therapsida: Cynodontia) from the Upper Permian Usili Formation, Tanzania
    (Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, 2009-12) Weide, D. Marie; Sidor, Christian A.; Angielczyk, Kenneth D.; Smith, Roger M.H.
    Procynosuchus, the best-known Permian cynodont, has a remarkably broad geographic range, with records stretching from southern Africa to Europe. Fossils of Procynosuchus are most common in the Upper Permian Dicynodon Assemblage Zone of South Africa, but also occur in coeval East African rocks. Currently, there is one documented occurrence from the Madumabisa Mudstone Formation of Zambia, and two specimens from the Usili (=Kawinga) Formation of Tanzania. The Tanzanian specimens include a poorly preserved, incomplete skull and a partial cranium originally attributed to Parathrinaxodon proops. The latter is now considered a subjective junior synonym of Procynosuchus delaharpeae. Here we report on a new specimen collected in 2007 near the base of Kingori Mountain in Tanzania. It preserves the postorbital region of the skull and the posterior portions of both lower jaws, each containing several intact teeth. A well-preserved postcanine tooth exhibits the dental hallmarks of Procynosuchus and permits unambiguous referral to this taxon. Recent fieldwork corroborates previous suggestions that the Usili tetrapod fauna includes representatives of the Tropidostoma, Cistecephalus and Dicynodon assemblage zones of South Africa. Moreover, the presence of several endemic Usili taxa (e.g. Katumbia, Kawingasaurus, Peltobatrachus), suggests that a straightforward correlation between the Usili tetrapod fauna and a particular assemblage zone from the Beaufort Group may not be possible.