Abstract Outcrops of the Ordovician System in South Africa are extensive; they cover significant portions of the Northern, Western and Eastern Cape provinces as part of the Cape Fold Belt as well as the KwaZulu-Natal Province as supracrustal cover overlying the Natal sector of the Paleoproterozoic Namaqua-Natal metamorphic province. Within the Cape Fold Belt, Ordovician rocks of the Table Mountain Group (Piekenierskloof, Graafwater, Peninsula, Pakhuis and Cedarberg formations as well as the enigmatic Sardinia Bay Formation) outcrop extensively whilst pre-Cape rocks of the Kansa Group (Vaartwell, Uitvlug, Gezwinds Kraal and Schoongezigt formations) and Schoemanspoort Formation are present within the Kango Inlier encapsulated by the fold belt. The Natal Group (Durban and Mariannhill formations) is entirely located within KwaZulu-Natal. For the most part, these metasiliciclastic rocks are markedly unfossiliferous except for the world class fossil deposits of the Cedarberg Formation and important trace fossil sites in the Graafwater, Peninsula and Pakhuis formations. The lack of palaeontological material and other accurate geochronological proxies in these successions (as well as those of the Kansa and Natal groups and Schoemanspoort Formation) makes estimations of relative age constraints tenuous at best and difficult to correlate with global Ordovician chronostratigraphic frameworks. Regardless of the challenges faced in correlating these rocks within global frameworks, these rocks provide a unique low latitude glimpse into Earth surface processes and the feedback loops that ensued within the biological realm along the southern margin of Gondwana.
The Witzand Formation forms the youngest subdivision of the Cenozoic Sandveld Group and was named after the Witzand homestead about 40 km north of Cape Town, where the formation is well developed. The formation essentially comprises whitish, unconsolidated, coastal calcareous dunes of Holocene age. The combination of a summer- dry Mediterranean climate and the powerful regional, obliquely onshore southerly winds (driven by the South Atlantic Anticyclone) have resulted in the evolution dune plumes that extend up to 15 km inland. The plumes are sporadically distributed along the southern west coast from False Bay to Elands Bay and are best developed updrift (north) of river mouths.
The early-branching crocodylomorph species Notochampsa istedana is known from a single South African specimen collected more than 100 years ago. This species is potentially important for understanding early crocodylomorph evolution, but it is of uncertain taxonomic status and its stratigraphic position is poorly constrained. Here we reinvestigate the anatomy, taxonomy, systematics and biostratigraphy of the holotype specimen, SAM-PK-4013. SAM-PK-4013 has a unique suite of features that distinguish it from the closely related taxa Orthosuchus and Protosuchus. These features include the length and shape of the dentary symphysis, the number and shape of dentary teeth, and the number of dorsal ribs with expanded intercostal ridges. Notochampsa is therefore a valid taxon, and our phylogenetic analysis recovers it as sister to Orthosuchus, in a monophyletic Notochampsidae. Notochampsa and Orthosuchus share a ventrally expanded squamosal flange and expanded intercostal ridges on the dorsal ribs. Notochampsidae is in turn sister to Protosuchidae, forming the monophyletic group Notochampsoidea. Fieldwork and stratigraphic revisions show definitively that SAM-PK-4013 is from the Clarens Formation, approximately ∼65 m above the Elliot contact, ageing Notochampsa to the Pliensbachian stage, a period of vertebrate body fossil scarcity. Thus, Notochampsa istedana is the youngest known occurrence of a crocodylomorph (and vertebrate body fossil) from the Karoo Basin of South Africa.
Living reptiles include more than 20,000 species with disparate ecologies. Direct anatomical evidence from Neodiapsida, which includes the reptile crown-group Sauria and its closest extinct relatives, shows that this diversity originates from a single common reptilian ancestor that lived some 255 million years ago in the Paleozoic. However, the evolutionary assembly of crown reptile traits is poorly understood due to the lack of anatomically close outgroups to Neodiapsida. We present a substantially revised phylogenetic hypothesis, informed by new anatomical data derived from high-resolution synchrotron tomography of Paleozoic reptiles. We find strong evidence placing the clade Millerettidae as a close sister to Neodiapsida, which uniquely share a suite of derived features among Paleozoic stem reptiles. This grouping, for which we name the new clade Parapleurota, replaces previous phylogenetic paradigms by rendering the group Parareptilia as a polyphyletic assemblage of stem reptiles, of which millerettids are the most crownward. Our analysis presents hypotheses that resolve long-standing issues in Paleozoic reptile evolution, including the placement of captorhinids on the amniote stem lineage and firm support for varanopids as synapsids, which taken together provide a greatly improved fit to the observed stratigraphic record. Optimizations of character evolution on our phylogenetic hypothesis reveals gradual assembly of crown reptile anatomy, including a Permian origin of tympanic hearing, the presence of a lower temporal fenestra in the amniote common ancestor, with subsequent modifications on the reptile stem lineage, leading to the loss of the lower temporal bar. This evolutionary framework provides a platform for investigating the subsequent radiations of the reptile crown group in the Early Triassic, including the lines leading to dinosaurs (including birds), crocodilians, lepidosaurs, and extinct marine reptiles.
The Cape Supergroup forms a regionally extensive and extremely thick Ordovician to Carboniferous succession of sedimentary rocks in southwestern South Africa.It includes the Lower-Middle Ordovician-lowermost Devonian Table Mountain Group, which incorporates the uppermost Ordovician Soom Shale Lagerstätte (within the Cedarberg Formation).The Soom Shale Lagerstätte accumulated in an unusual cold-water setting, associated with the decaying South African ice sheet, towards the end of the Hirnantian glaciation.The deposits of this glacial mar ine environment, characterised by anoxic bottom waters, preserve a highly unusual marine biota.It includes specimens exhibiting exceptional preservation of their soft tissues in clay min erals.Overlying deposits of the Soom Shale are shales and thin sandstones ascribed to the Disa Member that accumulated in a shoreface-shelf setting.Associated with these deposits are relict Soom taxa, in addition to a handful of Clarkeia-type brachiopod faunas, suggesting a probable earliest Silurian age for the upper part of the Cedarberg Formation.Previous palynological investigations of the Soom Shale have yielded typical marine elements, including chitinozoans, scolecodonts and rare acritarchs, but also common terrestrial elements in the form of dispersed spore tetrads.The latter are historically important as they represent an early report, by Jane Gray and colleagues, of dispersed cryptospore tetrads and were the first evidence for early land plants from Africa south of the Sahara (Ordovician eastern Gondwana at 30˚ S).Herein we report on a palynological investigation of an exposure of the Cedarberg Formation from the northernmost outcrops of the Cape Supergroup at Matjiesgoedkloof, Western Cape Province.Recently the sedimentology and ichnology of the underlying ice-marginal shallow-marine deposits of the Pakhuis Formation were described.Although macrofossils have not been recovered from these strata, they yield a fascinating ichnofauna that is diverse and disparate, comprising trackways and burrows.These show colonisation of glacial deposits by makers of burrows and trackways that lived in brackish water conditions as ice sheets re treated.Our palynological investigation yielded assemblages of abundant and well-preserved palynomorphs.Although of moderate-high thermal maturity, they are much less coalified than palynomorphs from the more southerly exposures.Surprisingly, the assemblages are domi nated by land plant spores with extremely rare, if any, marine palynomorphs.This may be a consequence of high freshwater influx from the decaying ice sheet's glaciers excluding normal marine biota (although the ichnological evidence demonstrates the presence of at least some organisms).The dispersed spore assemblage is somewhat unusual in that it is dominated by tetrads to the exclusion of monads and dyads.Coeval assemblages from similar palaeolatitudes in Gondwana (e.g. from the Arabian Plate) are far more diverse.This possibly reflects the close proximity of the vegetation to the ice sheet.
Millerettidae are a group of superficially lizard-like Permian stem reptiles originally hypothesized as relevant to the ancestry of the reptile crown group, and particularly to lepidosaurs and archosaurs. Since the advent of cladistics, millerettids have typically been considered to be more distant relatives of crown reptiles as the earliest-diverging parareptiles and therefore outside of ‘Eureptilia’. Despite this cladistic consensus, some conspicuous features of millerettid anatomy invite reconsideration of their relationships. We provide a detailed description of the late Permian millerettid Milleropsis pricei using synchrotron X-ray phase-contrast micro-computed tomography focusing on the cranial anatomy of three individuals known from a burrow aggregation. Our data reveal a suite of neuroanatomical features Milleropsis shares with neodiapsids that are absent both in other ‘parareptiles’ and in early diverging groups of ‘eureptiles’. Traits shared between Milleropsis and neodiapsids include: the presence of a tympanic emargination on the quadrate, quadratojugal and squamosal, the loss of epipterygoid contribution to the basicranial articulation suggesting a more kinetic palatoquadrate, the absence of a sphenethmoid and the pathway of the abducens nerve through the braincase. Our findings suggest that the early reptile neurocranium, a region poorly sampled in phylogenetic analyses due to relative visual inaccessibility and poor preservation, has the potential to inform the phylogenetic relationships of early reptiles.
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