New papers in a special issue ofÂ
South African Journal of Geology
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R.M.H. Smith, B.S. Rubidge, M.O. Day & J. Botha (2020)
Introduction to the tetrapod biozonation of the Karoo Supergroup.
South African Journal of Geology 123(2): 131-140
doi:
https://doi.org/10.25131/sajg.123.0009https://pubs.geoscienceworld.org/gssa/sajg/article-abstract/123/2/131/587464/Introduction-to-the-tetrapod-biozonation-of-theThe main Karoo Basin of South Africa contains the most abundant, diverse, and time expansive record of terrestrial vertebrates around the Palaeozoic-Mesozoic transition. This 10 km thick sedimentary succession accumulated in a large intracratonic, retro-arc, foreland basin (Johnson 1991; Catuneanu et al. 2005) in front of the rising Cape Fold Belt portion of the Gondwanide Mountain range that fringed the southern margin of Gondwana. Today, rocks of the Karoo Supergroup have a spatial distribution of some 300 000 km2 (Smith 1990), which is more than one-half the land surface of South Africa.
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B.S. Rubidge & M.O. Day (2020)
Biostratigraphy of the Eodicynodon Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa.
South African Journal of Geology 123(2): 141-148.
doi:
https://doi.org/10.25131/sajg.123.0010https://pubs.geoscienceworld.org/gssa/sajg/article-abstract/123/2/141/587456/Biostratigraphy-of-the-Eodicynodon-Assemblage-ZoneThe middle Permian Eodicynodon Assemblage Zone is the lowermost biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup) and occurs in the southwestern part of the main Karoo Basin. It is host to a diverse assemblage of basal therapsid genera of which Eodicynodon is the most abundant. The biozone reaches a maximum thickness of 1 100 m in the Prince Albert Road area and thins to the east and west. The biozone corresponds to the Combrinkskraal and Grootfontein members of the Abrahamskraal Formation, directly overlies the Waterford Formation of the Ecca Group, and records the earliest middle Permian terrestrial environments of Gondwana. Rocks of the biozone were deposited along the southern shoreline of the Karoo Basin in a subaerial delta plain environment as part of large-scale fan systems draining to the north and northeast within a second-order highstand systems tract.
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The Tapinocephalus Assemblage Zone is the second oldest tetrapod biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup), biostratigraphically positioned between the underlying Eodicynodon and overlying Endothiodon assemblage zones. It is characterised by a rich fossil tetrapod assemblage comprising basal members of most therapsid clades, but particularly dinocephalians such as Moschops capensis and basal pareiasaurs such as Bradysaurus in co-occurrence with the pylaecephalid dicynodonts Robertia and Eosimops. It corresponds to the upper two thirds of the Abrahamskraal Formation, is Capitanian (Guadalupian) in age, and reaches a maximum thickness of around 1500 m. The biozone is here separated into two subzones: a lower Eosimops -- Glanosuchus Subzone and an upper Diictodon -- Styracocephalus Subzone. The contact between the two subzones is defined by the first appearance of Diictodon feliceps, which closely corresponds to the base of the Moordenaars Member. The uppermost part of the biozone contains the Capitanian mass extinction and the low diversity fauna in its immediate aftermath. The zone is terminated by the first appearance of Endothiodon bathystoma
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M.O. Day & R.M.H. Smith (2020)
Biostratigraphy of the Endothiodon Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa.
South African Journal of Geology 123(2): 165-180.
doi:
https://doi.org/10.25131/sajg.123.0011https://pubs.geoscienceworld.org/gssa/sajg/article-abstract/123/2/165/587460/Biostratigraphy-of-the-Endothiodon-Assemblage-ZoneThe Endothiodon Assemblage Zone is the third oldest tetrapod biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup). It is situated between the underlying Tapinocephalus and overlying Cistecephalus assemblage zones and in the southwestern part of the basin corresponds to the majority of the Poortjie and Hoedemaker members of the Teekloof Formation. It is characterised by the dicynodont genus Endothiodon, especially in the lower part of assemblage zone, and records early ecosystem recovery from the Capitanian mass extinction. It also contains the lowest occurrence in the Karoo Basin of cynodont therapsids, eutherocephalians, bidentalian dicynodonts, and diapsids. The biozone reaches a maximum thickness of around 250 m in the southwestern part of the basin. We propose a two-fold subdivision into a lower Lycosuchus - Eunotosaurus Subzone (equivalent to the upper two-thirds of the former Pristerognathus Assemblage Zone) and an upper Tropidostoma - Gorgonops Subzone (equivalent to the former Tropidostoma Assemblage Zone), with the contact deïned by the ïrst appearance of Tropidostoma dubium. The Endothiodon Assemblage Zone is terminated by the ïrst appearance of Aulacephalodon bainii.
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The late Permian (Lopingian) Cistecephalus Assemblage Zone (CiAZ) of the Karoo Supergroup in South Africa has recently been radiometrically-dated to range from 256 to 255 My. It encompasses approximately one million years of the late Wuchiapingian epoch, at a time when the ancient intra-continental lowlands of southern Gondwana had fully recovered from the end-Guadalupian mass extinction. The diverse Cistecephalus Assemblage Zone fauna is dominated by the small herbivorous dicynodonts Diictodon, Pristerodon and the molelike Cistecephalus, along with a range of larger dicynodont herbivores including Oudenodon, Aulacephalodon, Rhachiocephalus, Dinanomodon and rare Endothiodon. The attendant large carnivores include the gorgonopsians Aelurognathus, Rubidgea, and Smilesaurus, while smaller carnivores are represented by eutherocephalians (e.g., Ictidosuchoides, Ictidosuchops) and small gorgonopsians (e.g., Aloposaurus, Scylacocephalus). Of the parareptiles, the large-bodied taxon Pareiasaurus is most common, with the diminutive pareiasaurs Anthodon, Nanoparia, and Pumiliopareia making their first appearance. Lithostratigraphically, the biozone for the most part coincides with the arenaceous Oukloof and lower Steenkampsvlakte members in the western sub-basin and the equivalent Oudeberg and lower Daggaboersnek members in the east, where it reaches its maximum thickness of 300 m. The Cistecephalus Assemblage Zone thins westwards to 120 m at Teekloof Pass, and eastwards to approximately 100 m near the town of Fort Beaufort.
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The name Daptocephalus Assemblage Zone (DaAZ) is re-instated for vertebrate assemblages of the uppermost Permian strata (Balfour, upper Teekloof, and Normandien formations) of South Africaâs main Karoo Basin (MKB). This involved taxonomic revision of the dicynodontoid "Dicynodon" sensu lato, reviving Daptocephalus leoniceps, and revising the stratigraphic ranges of co-occurring index taxa (Theriognathus microps, Procynosuchus delaharpeae) of the Dicynodon Assemblage Zone (DiAZ) as it was known. This work has demonstrated the appearance of index taxa below the stratigraphically defined DiAZ. Moreover, the first appearance of Lystrosaurus maccaigi and Moschorhinus kitchingi in the upper reaches of the biozone calls for the establishment of a two-fold subdivision of the current DaAZ into lower (Dicynodon-Theriognathus) and upper (Lystrosaurus maccaigi-Moschorhinus) subzones. The biostratigraphic utility of Daptocephalus and other South African dicynodontoids outside of the MKB is limited due to basinal endemism at the species level and varying temporal ranges of dicynodontoids globally. Accordingly, their use is recommended only for correlation within the Karoo Basin at this stage.
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The name Daptocephalus Assemblage Zone (DaAZ) is re-instated for vertebrate assemblages of the uppermost Permian strata (Balfour, upper Teekloof, and Normandien formations) of South Africaâs main Karoo Basin (MKB). This involved taxonomic revision of the dicynodontoid "Dicynodon" sensu lato, reviving Daptocephalus leoniceps, and revising the stratigraphic ranges of co-occurring index taxa (Theriognathus microps, Procynosuchus delaharpeae) of the Dicynodon Assemblage Zone (DiAZ) as it was known. This work has demonstrated the appearance of index taxa below the stratigraphically defined DiAZ. Moreover, the first appearance of Lystrosaurus maccaigi and Moschorhinus kitchingi in the upper reaches of the biozone calls for the establishment of a two-fold subdivision of the current DaAZ into lower (Dicynodon-Theriognathus) and upper (Lystrosaurus maccaigi-Moschorhinus) subzones. The biostratigraphic utility of Daptocephalus and other South African dicynodontoids outside of the MKB is limited due to basinal endemism at the species level and varying temporal ranges of dicynodontoids globally. Accordingly, their use is recommended only for correlation within the Karoo Basin at this stage.
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P.J. Hancoxm, J. Neveling & ÂB.S. Rubidge (2020)
Biostratigraphy of the Cynognathus Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa.
South African Journal of Geology 123(2): 217-238.
doi:
https://doi.org/10.25131/sajg.123.0016https://pubs.geoscienceworld.org/gssa/sajg/article-abstract/123/2/217/587465/Biostratigraphy-of-the-Cynognathus-Assemblage-ZoneThe Cynognathus Assemblage Zone is the youngest tetrapod biozone of the Beaufort Group (Tarkastad Subgroup, Karoo Supergroup). It is situated between the underlying Lystrosaurus declivis Assemblage Zone and the base of the overlying Molteno Formation (Stormberg Group) and corresponds to the entire Burgersdorp Formation. It is characterised by the presence throughout of the cynodont genus Cynognathus. The biozone reaches a maximum thickness of around 650 m in the southeast part of the basin and thins dramatically to the north, where it is only a maximum of 50 m thick. We here propose a three-fold subdivision into a lower Langbergia-Garjainia Subzone, a middle Trirachodon-Kannemeyeria Subzone and an upper Cricodon-Ufudocyclops Subzone. The basal contact is deïned biostratigraphically by the ïrst appearance of Cynognathus crateronotus and Langbergia modisei. The Cynognathus Assemblage Zone lacks a deïned biostratigraphic upper limit, being unconformably terminated by the base of the overlying Molteno Formation, which lacks a terrestrial vertebrate fossil record other than trackways.
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The Scalenodontoides Assemblage Zone (SAZ) is the oldest fossil tetrapod biozone of the Stormberg Group (Karoo Supergroup) and preserves the oldest dinosaur bearing deposits in the Karoo Basin. The SAZ represents a revision of the âEuskelosaurusâ Range Zone, whose taxonomic basis has been undermined because âEuskelosaurusâ is well demonstrated to be a nomen dubium. Recent qualitative and quantitative investigations into the biostratigraphy of the Elliot and Clarens formations have resulted in the ïrst biostratigraphic review of all lower Elliot Formation (lEF) taxa in nearly 40 years. Thus, we replace the âEuskelosaurusâ Range Zone with a new biostratigraphic assemblage zone, the Scalenodontoides Assemblage Zone (SAZ). Named after the traversodontid cynodont Scalenodontoides macrodontes, which co-occurs with the sauropodomorphs Blikanasaurus cromptoni and Melanorosaurus readi. The SAZ is currently accepted to range in age between the upper Norian and Rhaetian. Our new biozone, which reaches a maximum thickness of ~200 m, is wholly contained within the lower Elliot Formation (Stormberg Group, Karoo Supergroup).
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P.A. Viglietti, B.W. McPhee, E.M. Bordy, L. Sciscio, P.M. Barrett, R.B.J. Benson, S. Wills, K.E.J. Chapelle, K.N. Dollman, C. Mdekazi & J.N. Choiniere (2020)
Biostratigraphy of the Massospondylus Assemblage Zone (Stormberg Group, Karoo Supergroup), South Africa.
South African Journal of Geology 123(2): 249-262.
doi:
https://doi.org/10.25131/sajg.123.0018https://pubs.geoscienceworld.org/gssa/sajg/article-abstract/123/2/249/587462/Biostratigraphy-of-the-Massospondylus-Assemblage The Massospondylus Assemblage Zone is the youngest tetrapod biozone in the Karoo Basin (upper Stormberg Group, Karoo Supergroup) and records one of the oldest dinosaur dominated ecosystems in southern Gondwana. Recent qualitative and quantitative investigations into the biostratigraphy of the lower and upper Elliot formations (lEF, uEF) and Clarens Formation in the main Karoo Basin resulted in the ïrst biostratigraphic review of this stratigraphic interval in nearly four decades, allowing us to introduce a new biostratigraphic scheme, the Massospondylus Assemblage Zone (MAZ). The MAZ expands upon the Massospondylus Range Zone by including the crocodylomorph Protosuchus haughtoni and the ornithischian Lesothosaurus diagnosticus as two co-occurring index taxa alongside the main index taxon, the sauropodomorph Massospondylus carinatus. With a maximum thickness of ~320 m in the southeastern portion of the basin, our new biozone is contained within the uEF and Clarens formations (upper Stormberg Group), however, based on vertebrate ichnofossils evidence, it may potentially extend into the sedimentary units of the lowermost Drakensberg Group. We do not propose any further subdivisions, and do not consider the Tritylodon Acme Zone (TAZ) as a temporal biostratigraphic marker within the MAZ. The MAZ is currently accepted to range in age between the Hettangian and Pliensbachian, however a faunal turnover, which observes an increase in the diversity of dinosaur clades, crocodylomorph, and mammaliaform taxa in the lower uEF, could reïect effects of the end-Triassic extinction event (ETE).
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