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Re-uniting lost continents – fossil reptiles from the ancient Karoo and their wanderlust.
... Covering an area of ∼600,000 km 2 in South Africa and all of Lesotho (Figure 1), the main Karoo Basin is the largest sedimentary depocenter that formed in southwestern Gondwana from the Late Paleozoic to Middle Mesozoic (Johnson et al., 1996;. The basin is notable for containing a succession, formally named the Karoo Supergroup, which represents a geological history of ∼120 Myr in duration (Figure 1- Johnson et al., 1996;Rubidge, 2005). The Karoo Supergroup, being the most widespread stratigraphic unit in southern Africa, fills the similar aged basins to the MKB that are spread across the region and all the way to the Sahara Desert in the north (Catuneanu et al., 1998;Catuneanu et al., 2005). ...
... The Karoo Supergroup, being the most widespread stratigraphic unit in southern Africa, fills the similar aged basins to the MKB that are spread across the region and all the way to the Sahara Desert in the north (Catuneanu et al., 1998;Catuneanu et al., 2005). The Karoo Supergroup preserves the record of major geological and biotic events that range from the formation of Permo-Carboniferous glacial deposits to the extrusion and intrusion of Lower Jurassic igneous complexes as well as several mass extinction events (e.g., end-Capitanian, end-Permian, and end-Triassic: Johnson et al., 1996;Rubidge, 2005;Rubidge et al., 2013;Day et al., 2015). ...
... The Beaufort Group, which is the Middle Permian to Middle Triassic part of the Karoo Supergroup, represents the first continental fluvial and lacustrine strata in the MKB. The succession is >2500 m thick and consists of mainly mudstones and sandstones, which preserve an outstandingly rich and fairly diverse vertebrate fossil heritage that is dominated by premammalian land-dwelling tetrapods (Keyser and Smith, 1978;Hancox and Rubidge, 2001;Rubidge, 2005). This abundant therapsid fossil fauna not only allowed the biostratigraphic subdivision of the Beaufort Group into eight vertebrate assemblage zones ( Figure 1C), but also turned the unit into a global biostratigraphic standard for the Middle Permian to Early Triassic continental vertebrates (Rubidge, 2005;Viglietti et al., 2016;Day and Rubidge, 2020). ...
The main Karoo Basin of southern Africa contains the continental record of the end-Triassic, end-Permian, and end-Capitanian mass extinction events. Of these, the environmental drivers of the end-Capitanian are least known. Integrating quantitative stratigraphic architecture analysis from abundant outcrop profiles, paleocurrent measurements, and petrography, this study investigates the stratigraphic interval that records the end-Capitanian extinction event in the southwestern and southern main Karoo Basin and demonstrates that this biotic change coincided with a subtle variation in the stratigraphic architectural style ∼260 Ma ago. Our multi-proxy sedimentological work not only defines the depositional setting of the succession as a megafan system that drained the foothills of the Cape Fold Belt, but also attempts to differentiate the tectonic and climatic controls on the fluvial architecture of this paleontologically important Permian succession. Our results reveal limited changes in sediment sources, paleocurrents, sandstone body geometries, and possibly a constant hot, semi-arid paleoclimate during the deposition of the studied interval; however, the stratigraphic trends show upward increase in 1) laterally accreted, sandy architectural elements and 2) architectural elements that build a portion of the floodplain deposits. We consider this to reflect a long-term retrogradational stacking pattern of facies composition that can be linked to changes on the medial parts of southward draining megafans, where channel sinuosity increased, and depositional energy decreased at the end-Capitanian. The shift in the fluvial architecture was likely triggered by basin-wide allogenic controls rather than local autogenic processes because this trend is observed in the coeval stratigraphic intervals from geographically disparate areas in the southwestern and southern main Karoo Basin. Consequently, we propose that this regional backstepping most likely resulted from tectonic events in the adjacent Cape Fold Belt.
... No radiometric dates exist for the Cynognathus AZ and the age is derived from faunal correlation of the various subzones. Based on the correlation of the Langbergia-Garjainia Subzone with the Parotosuchus Fauna of Russia, the age of this subzone is best placed as Early Triassic (late Olenekian; Hancox et al., 1995;Shishkin et al., 1995;Hancox and Rubidge, 1997;Shishkin et al., 2000;Neveling, 2004;Shishkin et al., 2004;Rubidge, 2005;Gower et al., 2014). ...
... The Trirachodon-Kannemeyeria Subzone may be correlated with lower levels of the upper Omingonde Formation of Namibia (Keyser, 1973a,b), the lower horizon of the Ntawere Formation of Zambia (Cruickshank, 1965(Cruickshank, , 1986Peecook et al., 2013Peecook et al., , 2018Wynd et al., 2018), the uppermost Kingori/lower Lifua members of Tanzania (Cruickshank, 1965(Cruickshank, , 1986Smith et al., 2018), the upper member of the Fremouw Formation of Antarctica (Sidor et al., 2008), the lower Ermaying Formation of China and the Eryosuchus Fauna of Russia. Various age estimates have been given in the past, but in general this subzone is assigned a Middle Triassic (early Anisian) age (Keyser, 1973a, b;Hammer, 1995;Hancox, , 2000Rubidge, 2005;Butler et al., 2015;Liu et al., 2018; but see Ottone et al., 2014 as discussed above). ...
... Cynodonts from the lower Ntawere Formation include Cynognathus and Diademodon whereas Luangwa, Cricodon and an undescribed taxon occur in the upper Ntawere Formation (Sidor et al., 2016;Peecook et al., 2018). Currently, the interval containing the NMCs Cynognathus and Diademodon and the dicynodont Kannemeyeria is correlated to the Trirachodon-Kannemeyeria subzone of the Cynognathus AZ in the MKB, whereas the presumably younger horizon containing Cricodon, stahleckeriid dicynodonts, capitosauroid temnospondyls, and dinosauriforms is correlated to the Cricodon-Ufudocyclops subzone (Rubidge, 2005;Angielczyk et al., 2014;Peecook et al., 2018;Hancox et al., 2020). ...
Terrestrial Triassic assemblages are an important component of the heritage of Argentina, particularly because of their diverse record of fossil vertebrates. Triassic basins from western Argentina have a good representation of therapsids, a lineage that includes a series of stem extinct groups plus crown Mammalia. Because of their diversity and abundance, non-mammaliaform cynodonts are the most conspicuous therapsids in the Argentinean Triassic. Cynodonts have been intensively researched in Argentina since the 1960s and continue to provide key advances in the understanding of the evolution and biology of the lineage. Here we offer a summary of Triassic Argentinean non-mammaliaform cynodonts, presenting a historical context of research on this group, and highlighting seminal contributions of Triassic Argentinean cynodonts to the global knowledge of the group. To provide a Gondwanan context we review the cynodont record in the two other places where the lineage is best represented: Brazil and southern Africa (including Madagascar), highlighting commonalities in the Argentinean record with these places. Considering the important role of non-mammaliaform cynodonts in the interpretation of the origin of mammals, we provide a historical account on the contribution of Argentinean, and Gondwanan, cynodonts to the understanding of this topic. This is supplemented with a summary of the progression of phylogenetic ideas and hypotheses for all non-mammaliaform cynodonts and for the most prolifc subgroups represented in western Gondwana.
... This tripartite subdivision has found widespread acceptance in the literature (e.g. Hopson and Kitching, 2001;Rubidge 2005;Abdala and Smith 2009;Fröbisch 2009;Martinelli et al., 2009;Abdala and Ribeiro, 2010;Nesbitt et al., 2013;Peecook et al., 2013;Angielczyk et al., 2014;Sidor et al. 2014a and b;Rubidge et al., 2016, Wynd et al., 2018Hendrickx et al., 2019) and whilst various authors have utilised the informal subdivision in their correlations, no formal subdivision of the Cynognathus Assemblage Zone has been published. ...
... Neveling (2002Neveling ( , 2004 and Neveling et al. (2005) demonstrated the southern limit of this fauna could be extended as far as the towns of Tarkastad and Queenstown. This new biozone was previously referred to as the "lower zone", "lowermost subzone" Shishkin et al., 1995),"subzone A fauna" (Hancox and Rubidge 1997;, the "Kestrosaurus grouping" (Shishkin 2000), the "Kestrosaurus Assemblage Zone" (Neveling 2002(Neveling , 2004 and Cynognathus A biozone (Rubidge, 2005). ...
... Based on correlation with ammonite-containing rocks from the Cis-Caspian depression and western Kazakhstan, the Parotosuchus Fauna is dated as Early Triassic (late Olenekian; Shishkin et al., 2000). Based on the correlation proposed above an Early Triassic age has been accepted by most authors for the Langbergia-Garjainia Subzone Shishkin et al., 1995;Hancox and Rubidge 1997;Shishkin et al., 2000;Neveling, 2004;Shishkin et al., 2004;Rubidge, 2005;Gower et al., 2014). ...
The 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 defined biostratigraphically by the first appearance of Cynognathus crateronotus and Langbergia modisei. The Cynognathus Assemblage Zone lacks a defined biostratigraphic upper limit, being unconformably terminated by the base of the overlying Molteno Formation, which lacks a terrestrial vertebrate fossil record other than trackways.
... Deposition of sediments of the Eosimops -Glanosuchus Subzone occurred on extensive alluvial plains that extended north and east from the Cape Fold Mountains, a part of the Gondwanides chain of mountains situated along the southern margin of Gondwana (Rubidge, 2005). Rivers flowing off the mountains formed both low-and high-sinuosity fluvial channels and deposited sediment within channels and, less frequently, as overbank crevasse splays (Paiva, 2017;Stear, 1980;Smith, 1990). ...
... Rivers flowing off the mountains formed both low-and high-sinuosity fluvial channels and deposited sediment within channels and, less frequently, as overbank crevasse splays (Paiva, 2017;Stear, 1980;Smith, 1990). Initially, this alluvial plain was constrained to the southern margin of the basin but throughout the Capitanian the Ecca sea retreated (Rubidge, 2005). The climate at the time of deposition was semi-arid which resulted in fluctuations of discharge causing flooding of the perennial larger rivers and ephemeral flow in the smaller distributaries Keyser, 1995, Stear, 1980). ...
... Deposition of rocks of the Diictodon -Styracocephalus Subzone occurred on extensive alluvial plains that extended north and east from the Cape Fold Mountains, a part of the Gondwanides chain of mountains situated along the southern margin of Gondwana (Rubidge, 2005). The upper Abrahamskraal Formation formed in a high energy, braided fluvial system (Paiva, 2015) with sediment deposited within channels and, less frequently, as overbank crevasse splays (Paiva, 2015;Stear, 1980;Smith, 1990). ...
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.
... The basin covers around 700,000 km² with siliciclastic rocks ranging in age from the Carboniferous to the Jurassic. The basin has recorded the climatic transition from ice-house to hot-house (McCarthy and Rubidge, 2005) with the fill of the basin comprising basal glacial tillite, deep-marine black shales, deltaic and fluvial sandstones and mudstones through to aeolian sandstones, with the sedimentary succession covered by flood basalts related to the breakup of Gondwana (Johnson et al., 2006). ...
... The onset of Karoo sedimentation occurred during the Late Carboniferous and continued until the break-up of Gondwana during the Middle Jurassic at ca. 183 Ma (Figure 2.6) (Johnson et al., 2006). A total sediment infill thickness of 12 km is attained within the southeastern part of the Main Karoo Basin, with sediment sourced from the north (Cargonian Highlands) as well as from the south (Cape Fold Belt mountain range) (McCarthy and Rubidge, 2005). Flint et al. (2011) contests that during the Ecca Group time there was no source area nearby and studies by , Andersson et al. (2004), Van Lente (2004) and King (2005) suggest the Cape Fold Belt was not emergent at the time of deep water deposition of the lower Karoo Supergroup. ...
... The stratigraphy of the Karoo Basin has primarily been constructed using vertebrate macrofossil assemblages (Broom, 1903;Von Huene, 1925, Von Huene andPompeckj, 1931;Kitching 1978). Vertebrate biozones have also played a role in models for the Karoo Basin development and its palaeoenvironmental reconstruction (Catuneanu et al., 1998;Rubidge, 2005;Smith, 1995). Temporal constraints for Karoo vertebrate biozones have been obtained by faunal correlation with better dated continental sedimentary deposits worldwide (Rubidge, 2005). ...
Energy shortages and sporadic, controlled blackouts have been a defining feature of South Africa’s aging national energy grid for more than a decade. To investigate local energy sources from shale gas, two boreholes were drilled in the southern Main Karoo Basin into the Permianaged Ecca Group by the Karoo Research Initiative. Borehole KZF-1 (Western Cape) intersected thick shale successions of the lower Ecca Group and revealed the stratigraphic duplication of the Whitehill (shale gas target) and Prince Albert Formations. This structural deformation was most likely as a result of the organic-rich formations, acting as a decollement for thrust faults related to the north-south directed compression of the Cape Orogeny. Reservoir compartmentalisation and gas escape along porous fault zones hinder hydrocarbon exploration in the area. Borehole KWV-1 (Eastern Cape) revealed thick successions of turbiditic sandstones and a moderately elevated geothermal gradient. The clastic rocks have low permeabilities and high thermal conductivities. Analysis of the petro- and thermophysical data from the Ripon
Formation sandstones, from both the core and nearby Ecca Pass outcrop location, show the potential of the formation as an Enhanced Geothermal Reservoir, with temperatures exceeding 100°C being suitable for energy production from a binary geothermal power plant. The comparison of combined gamma-ray logs, geothermal potential of samples (specific heat capacity, thermal diffusivity, and thermal conductivity) and lithological logs show a correlation between lithological composition and geothermal reservoir potential that can be identified in gamma-ray log patterns. These correlations can be extrapolated for purposes of geothermal exploration in non-cored nearby boreholes. The numerous pre-existing faults, decreasing from the basin’s southern margin towards the basin interior, elevate the risk of inducing seismic events from the use of reservoir stimulation techniques associated with energy exploration, as well as wastewater management associated with future extraction activities.
... Dicynodonts number among the most successful Permian and Triassic nonmammalian synapsids in terms of their species richness, abundance, and stratigraphic distribution. The clade was also cosmopolitan, with dicynodont fossils having been discovered on every continent (King 1992;Rubidge 2005;Fröbisch 2009). However, the detail with which the dicynodont faunas from particular areas are known varies greatly depending on factors such as available outcrop area and the cumulative collecting effort expended by paleontologists. ...
... We relocated one of those specimens (BP/1/3574) and confirm its identification. Anderson and Cruickshank (1978), King (1988King ( , 1992, Rubidge (2005), and Fröbisch (2009) ...
... Previous Reports: If our identification of SAM-PK-K7933 is correct, then Boonstra's (1938) report of this specimen is the first time a Zambian specimen of Pristerodon was mentioned in the literature, although it was not identified as such at the time. Drysdall and Kitching (1963) noted the occurrence of ''Parringtoniella'' at their Locality 3, but it is unclear whether they collected any of these specimens because all of the Pristerodon material we identified at the BP originated at their Locality 4. Anderson and Cruickshank (1978), Rubidge (2005), and Fröbisch (2009) all included Pristerodon in their compilations. King (1988) included ''Parringtoniella'' in the faunal list for Zambia, but later King (1992) suggested that this most likely was a synonym of Pristerodon. ...
... The Karoo Basin of southern Africa contains a clastic sedimentary rock record spanning the Late Carboniferous-Early Jurassic (Fig. 1). The Karoo Supergroup provides key information on the geochronological, litho-, bio-and magnetostratigraphic record of southern Africa (e.g., Du Toit, 1939;1954;Haughton, 1969;Kitching, 1977;Smith, 1990;Johnson et al., 1996;Bangert et al., 1999;Rubidge, 2005;Johnson et al., 2006;Barbolini, 2014;Sciscio et al., 2017a;Viglietti et al., 2018). The upper part of the Karoo succession, the Stormberg Group, is particularly abundant in Late Palaeozoic-very early Mesozoic trace and body fossil assemblages, currently used in the schematic biozonation schemes of the region (e.g., Ellenberger, 1970;Kitching and Raath, 1984;Olsen and Galton, 1984;Lucas and Hancox, 2001;Knoll, 2004;Knoll, 2005). ...
... The TJB and ETE placements are commonly associated with biostratigraphic, geochemical, chronostratigraphic and palaeomagnetic shifts (e.g., Raup and Sepkoski, 1982;Beerling and Berner, 2002;Tanner et al., 2004;Blackburn et al., 2013;Wotzlaw et al., 2014;Kent, et al., 2017). Both ichnofossil and body 3 fossil material, in conjunction with recently attained magnetostratigraphic profiles, have aided in providing a tentative global correlative TJB placement within the Elliot Formation (Kitching and Raath, 1984;Olsen and Galton, 1984;Anderson et al., 1998;Rubidge, 2005;Sciscio et al., 2017a). ...
... The Karoo Supergroup hosts an amazing georecord. An array of in-depth biostratigraphic studies have provided ample biostratigraphic global age correlations and are, in conjunction with lithostratigraphy, the primary age determining techniques utilised throughout the Karoo Supergroup (e.g., Rieck, 1973;Rieck, 1974;Rieck, 1976a, b, c;Kitching and Raath, 1984;MacRae, 1988;Cairncross et al., 1995;Rubidge et al., 1995;Smith, 1995;Hancox and Rubidge, 1996;Catuneanu et al., 1998;Olsen and Galton, 1984;Rubidge, 2005). Direct radiometric age dating, in contrast, has been sparse, with a few intermittent volcanogenic member and detrital zircon radioisotopic dates obtained from the Karoo Supergroup (Fig. 6). ...
The Elliot and Clarens formations (Stormberg Group) of the Karoo Supergroup famously preserve not only a dynamic suite of depositional environments spanning the Late Triassic to Early Jurassic, but also boast a diverse assemblage of trace and body fossils. Due to the nature of these assemblages spanning the globally correlative Triassic-Jurassic Boundary (TJB) and end-Triassic Extinction Event (ETE), the accuracy of temporal placement and correlation via the stratigraphic framework is paramount. Yet, a distinct lack of robust temporal framework and inconsistencies between the bio-, magneto- and lithostratigraphic records persist. This project sought to provide localized context for three key fossil-bearing localities (southwestern Lesotho), which could thereafter be applied both at a regional and global scale. In-depth facies, palaeocurrent and architectural element analyses illustrated an overall increase in palaeoclimatic aridity, as evidenced by the change in depositional system from the meandering fluvial dominated lower Elliot Formation to the aeolian Clarens Formation. Detrital zircon geochronology ascertained a temporal framework ranging from the Norian to Pliensbachian (216.7-190.5 Ma) Elliot Formation to the Sinemurian to Pliensbachian (190.5-186.7 Ma) Clarens Formation. These temporal constraints also support the presence of a regional paraconformity at the lower and upper Elliot contact. The geochronology additionally indicated a shared source provenance of recycled grains from the Cape Supergroup and older Karoo strata, interspersed with direct source inputs from proximal magmatic/metamorphic provinces. Ultimately, the greater temporal and palaeoecological resolution provided by this study promotes the better understanding of the early Mesozoic history of southern Gondwana and lays the foundations for future geochronological investigations.
... Historically, stratigraphic palaeontological work in the Beaufort Group tended to focus on the more southern (proximal) parts of the Main Karoo Basin. This is primarily a function of greater rock exposure resulting from the greater aridity and topography in the southern Karoo, and because non-marine deposition of the Beaufort Group was initially (prior to the Daptocephalus (Dicynodon) AZ) restricted to the proximal margin of the basin (see Rubidge 2005). The mid-Permian assemblage Fig. 1. ...
... Most previous studies of geographical differences between Permian-Triassic tetrapod assemblages have, however, considered the Main Karoo Basin as a single geographical unit, and have focused on the differences between basins and not within them (Rubidge 2005;Sidor et al. 2005Sidor et al. , 2013Angielczyk et al. , 2014aHuttenlocker & Sidor 2016;Olroyd & Sidor 2017). Both quantitative studies and qualitative observations suggest that provincialism in southern African dicynodonts increased from the Late Permian to Middle Triassic and that endemic taxa were present in all the southern African basins during this time (Angielczyk & Kurkin 2003;Sidor et al. 2005Sidor et al. , 2013Angielczyk 2007;Hancox et al. 2013;Button et al. 2017;Angielczyk et al. 2018;Kammerer et al. 2018;Peecook et al. 2018;Roopnarine et al. 2018b). ...
... Understanding of intrabasinal provincialism during the mid-Permian is more difficult to assess. This results from the paucity of fossil material identifiable to genus or species level, with assemblages being recognized as mid-Permian primarily based on the presence of dinocephalian therapsids in Tanzania (Simon et al. 2010), Zambia (Sidor et al. 2014) and Zimbabwe (Boonstra 1946(Boonstra , 1968Lepper et al. 2000;Munyikwa 2001;Rubidge 2005). These assemblages have therefore been ignored from quantitative analyses (Sidor et al. 2013;Button et al. 2017). ...
The rich fossil vertebrate record from the Beaufort Group, Main Karoo Basin, provides a global standard for mid‐Permian to Mid‐Triassic continental faunas. However, recent studies have demonstrated variability in the composition of contemporaneous faunas across Gondwana. This raises the question of how much the vertebrate faunas differ within the Karoo, where the taxonomic composition of vertebrate assemblage zones (AZs) is mostly considered to be uniform. Although fossil material is known from across the outcrop of the Beaufort Group, the lowest Beaufort strata have received little attention, particularly north of S31°10′. Here, we report two fossil tetrapod assemblages from the lowest Beaufort Group in the southern Free State Province, which represent the northernmost point at which the lowest Beaufort has been targeted for collecting. The lower assemblage is characterized by an abundance of the small dicynodont Eosimops and can thus be attributed to the Tapinocephalus AZ (Guadalupian), but the absence of dinocephalian or pareiasaurian material is unlike contemporaneous assemblages found further south. This suggests that the Tapinocephalus AZ was not uniform across the entire basin and highlights that the abundance, distribution and taxonomic composition of Karoo biozones may vary more than currently appreciated. The upper assemblage, characterized by the dicynodonts Oudenodon, Aulacephalodon and Dinanomodon, is attributable to the upper Cistecephalus AZ to lower Daptocephalus AZ. The juxtaposition of the lower Tapinocephalus AZ and upper Cistecephalus\lower Daptocephalus AZ in the southern Free State implies a stratigraphic gap from the Middle to Late Permian of up to 6 million years.
... It is noteworthy that Owen already noted the close similarity between the Early Triassic cynodont synapsids such as Galesaurus and mammals (Owen, 1876). At the beginning of the twentieth century, these pioneering efforts were continued by Robert Broom whose prolific research and unrivaled number of fossil discoveries during the first four decades of the last century first outlined the major steps in the evolution of synapsids leading to mammals (Rubidge, 2005). Finally, Thomas Henry Huxley (1865) and Richard Lydekker (1885) reported on skeletal remains of Triassic reptiles, synapsids, and amphibians from India in the second half of the nineteenth century. ...
... In Africa, expeditions led by Sterling Nesbitt and Chris Sidor in recent years have explored old and discovered many new localities yielding many, mostly Middle Triassic tetrapod remains in Tanzania and Zambia (Sidor & Nesbitt, 2017). In South Africa, Lesotho, and Zimbabwe, Broom's work on Triassic synapsids and other tetrapods from the Karoo has been continued with great success by other researchers, especially Bruce Rubidge, Roger Smith, and, most recently, Jonah Choiniere, from the University of the Witwatersrand (Rubidge, 2005;Smith et al., 2020). ...
... Historically, these Karoo fossils cemented plate tectonics as the leading 73 paradigm of geosciences, and more recently, due to improved radioisotopic dating, have given us 74 unprecedented insight into the waxing and waning of 120 myr of Life from the Permian to the Jurassic. 75Echoing the tetrapod diversity, the Karoo contains the richest trace fossil record in southern Africa, aThe Karoo Supergroup's wealth of animal, plant and trace fossils represents the most complete84 Permian-Jurassic continental succession in Gondwana(Rubidge 2005). This geoheritage has enhanced 85 global understanding of the impact that palaeoenvironmental changes had on continental ecosystems in 86 deep time and their role as drivers of evolutionary change. ...
... This geoheritage has enhanced 85 global understanding of the impact that palaeoenvironmental changes had on continental ecosystems in 86 deep time and their role as drivers of evolutionary change. The Karoo, noted for exceptional rock 87 outcrops, which facilitate geological and palaeontological study, is the only place in the world where 88such a time-extensive record of early tetrapod evolution is preserved in a single basin(Rubidge 2005). In 89 addition to being a pivotal area for the study of palaeoecology, biodiversity and evolution, the Karoo 90 offers great potential for sustainable geotourism, which is in its nascency. ...
The main Karoo Basin of South Africa and Lesotho preserves c. 120 myr of Earth's history. The sedimentary rocks of its Karoo Supergroup record massive environmental changes from the glacial Carboniferous to desert dunes and fiery flood basalts in the Early Jurassic. From the early Permian, the Karoo Basin was gradually filled with fluvial and lacustrine deposits, and the alluvial plains were successively colonised by a diverse suite of plants and animals. The fossils of these ancient inhabitants and their behavioural traces form an astounding Gondwanan geoheritage legacy in southern Africa, providing fossil evidence for the moving lithospheric plates and the effects of four mass extinctions and their subsequent biotic recovery. Here, we present six Karoo sites of global geoscientific importance that best display that heritage, with the caveat that these sites only touch upon the Karoo riches that are available for academic research and the emerging palaeotourism industry. It is our hope that these sites will become anchor points for a sustainable geoheritage future in southern Africa.
... The Transantarctic Mountains in Antarctica preserve several important early Mesozoic vertebrate fossil assemblages; those from the lower Fremouw Formation have been dated to the Early Triassic based on biostratigraphic correlation with the Lystrosaurus declivis Assemblage Zone in southern Africa, and the upper Fremouw assemblage is thought to be Middle Triassic in age based on correlation to the Cynognathus Assemblage Zone (e.g., Rubidge, 2005;Sidor et al., 2008Sidor et al., , 2014aFröbisch et al., 2010;Huttenlocker and Sidor, 2012;Hancox et al., 2013Hancox et al., , 2020Peecook et al., 2019;Smith et al., 2020). Several U-Pb zircon SIMS ages have recently been reported from the Fremouw Formation, sampled from Collinson Ridge (Elliot et al., 2017), one of the primary fossil-bearing areas (e.g., Peecook et al., 2019: Fig. 1). ...
... The age of the Cynognathus Assemblage Zone in the Karoo Basin is one of the most critical unresolved issues in Triassic vertebrate paleontology because fossils from these and potentially correlative strata have been the primary data for inferring the pace of recovery from the end-Permian mass extinction and large-scale biogeographic patterns (e. g., Shubin and Sues, 1991;Roopnarine et al., 2007;Angielczyk, 2012, 2015;Sahney and Benton, 2008;Irmis and Whiteside, 2012;Sidor et al., 2013). This fossil assemblage has long been assumed to be mostly Middle Triassic in age (e.g., Anderson and Anderson, 1970;Romer, 1970;Anderson, 1973;Keyser, 1973;Kitching, 1977;Keyser and Smith, 1978;Rubidge, 2005;Hancox et al., 2020), and fossil assemblages elsewhere in Namibia, Zambia, Tanzania, Antarctica, Brazil, and Argentina have been dated to the Middle Triassic based on vertebrate biostratigraphic correlation with these strata (e.g., Abdala and Smith, 2009;Abdala et al., 2013;Hancox et al., 2013Hancox et al., , 2020Peecook et al., 2017;Wynd et al., 2017;Smith et al., 2020;Mancuso and Irmis, 2020). Nonetheless, there are no independent age constraints (i.e., geochronology or marine index fossils) from the Cynognathus Assemblage Zone in the Karoo Basin that would allow confident assignment to the GSSP-defined Middle Triassic divisions of the geologic timescale. ...
Gondwanan sedimentary deposits preserve a rich archive of Triassic non-marine vertebrate evolution. This fossil record is integral to understanding early Mesozoic global change events, including the end-Permian and end-Triassic mass extinctions, Carnian Pluvial Episode, and macroevolutionary events such as the origin of dinosaurs. Until very recently, almost all of these fossil assemblages were dated by exclusively biostratigraphic means, which made robust correlation to the GSSP-defined timescale difficult. Furthermore, recent advances in radioisotopic dating and magnetostratigraphy have demonstrated that many of these biostratigraphic schemes were imprecise and that key index taxa have different first and last appearances across geographic space. Thankfully, over the past ten years, new radioisotopic and magnetostratigraphic age constraints from fossiliferous sequences in South America have allowed the revision of the absolute ages and relative correlation of key Gondwanan vertebrate assemblages.
Here, we review these geochronologic age constraints from South America, describe and revise their accuracy and uncertainties, present new U–Pb zircon age data for a key section in Venezuela, infer preliminary age models for these successions, and discuss what they mean for the correlation of fossiliferous Triassic units in Gondwana. This synthesis suggests that although radioisotopic age data are often numerous, the geological uncertainties associated with U–Pb zircon dates using micro-beam techniques (LA-ICPMS and SIMS) mean that the age of most sedimentary units cannot be constrained better than a precision of ± 3–5 Ma. Although CA-TIMS U–Pb zircon ages and ⁴⁰Ar/³⁹Ar ages can be more precise and accurate, they only result in well-constrained age models when multiple ages are available throughout the section (e.g., Ischigualasto-Villa Unión Basin of northwest Argentina), and even then, issues with lateral correlation within basins remain. Nonetheless, these data demonstrate that South America has high potential for developing a precise and accurate Triassic non-marine numerical timescale for Gondwanan vertebrate evolution.
... A reanalysis of the stratigraphy suggested that the Qingtoushan Formation is dated from the Roadian-Wordian and is positioned between the Yaogou Formation (early Guadalupian) and the Sunan Formation (Lopingian) (Liu et al. 2012;Liu 2018a). Based on the vertebrate assemblage from the top of the stratigraphic succession, the Dashankou fauna has been correlated with the Russian early Permian Parabradysaurus silantjevi assemblage zone (Sennikov and Golubev 2017), which indicates a Roadian age (Rubidge 2005;Liu et al. 2012;Liu 2018a). The therapsids from the Dashankou fauna are old enough to partially fill the abovementioned gap in our knowledge, the most notable being Raranimus for its inferred basal phylogenetic position (Liu et al. 2009). ...
... Here, the nasal process tapers posteriorly and shares a long and oblique suture with the nasal bone laterally (Fig. 1D). As in biarmosuchians and dinocephalians, the nasal process extends far beyond the level of the naris posteriorly (Hopson and Barghusen 1986) whereas it is usually shorter in pelycosaurs and more derived therapsids taxa (Romer and Price 1940;Abdala and Giannini 2000;Rubidge andSidor 2001, 2002;Sidor and Smith 2007;Kammerer 2016;Abdala et al. 2019). The anterior and lateral surfaces of the premaxilla are damaged by several holes but some of them can be interpreted as real foramina (foramina are connected Fig. 1A, B, and C). ...
The non-mammalian therapsids comprise a paraphyletic assemblage of Permian-Jurassic synapsids closely related to mammals that includes six major clades of largely unresolved phylogenetic affinity. Understanding the early evolutionary radiation of therapsids is complicated by a gap in the fossil record during the Roadian (middle Permian) known as Olson’s gap. Because of its early stratigraphic occurrence and its primitive features, Raranimus dashankouensis, from the Dashankou fauna (Rodian), Qingtoushan Formation (China), is currently considered the best candidate to fill this gap. However, it is known from only a single specimen, an isolated snout, which limits the amount of usable phylogenetic characters to reconstruct its affinities. In addition, understanding of the stratigraphy of the Qingtoushan Formation is poor. Here, we used CT scanning techniques to digitally reconstruct the bones and trigeminal canals of the snout of Raranimus in 3D. We confirm that Raranimus shares a high number of synapomorphies with more derived therapsids and is the only therapsid known so far to display a “pelycosaur”-like maxillary canal bearing a long caudal alveolar canal that gives off branches at regular intervals. This plesiomorphic feature supports the idea that Raranimus is basal to other therapsids.
... Only two pylaecephalid species are currently recognized, Robertia broomiana and Diictodon feliceps, and these species are united by distinctive characters such as the presence of a square-cut caniniform process that is angled medially relative to the sagittal plane of the skull, forming a notch between the anterior edge of the process and the maxillary alveolar margin; a tall, rounded cutting blade on the dentary table; and the presence of an ectepicondylar foramen on the humerus (e.g., King, 1988;Angielczyk and Kurkin, 2003a;Kammerer and Angielczyk, 2009). Robertia broomiana has been reported only from the Middle Permian Tapinocephalus Assemblage Zone (Rubidge, 1995(Rubidge, , 2005 of the Karoo Basin, South Africa (Boonstra, 1948;King, 1981aKing, , 1988King, , 1992Cluver and King, 1983;King and Rubidge, 1993;Keyser, 1993), whereas D. feliceps is much longer-ranging temporally and more widespread geographically. It first appears in the Tapinocephalus Assemblage Zone of the Karoo Basin, and becomes extinct close to the Permo-Triassic boundary in the upper Dicynodon Assemblage Zone (Rubidge, 1995;Smith and Ward, 2001;Ward et al., 2005;Smith and Botha, 2005;Botha and Smith, 2006). ...
... Precise stratigraphic ranges of different dicynodont genera in the Tapinocephalus Assemblage Zone still need to be determined and are the subject of a current field program. At this stage it is evident that the occurrence of increasingly derived dicynodonts along the Ecca-Beaufort contact as one progresses northward in the Basin supports the idea that the Beaufort-Ecca contact is diachronous and becomes younger in a northeasterly direction (Rubidge, 2005). This attests to the useful part that tetrapod fossils have played, together with sedimentology, in understanding Karoo Basin development. ...
We describe Prosictodon dubei, gen. et sp. nov., from the Abrahamskraal Formation, Karoo Basin, Middle Permian of South Africa. Diagnostic characters of P. dubei include postorbitals that slope ventrolaterally and overlap the parietals nearly completely; median anterior palatal ridges that converge with the posterior median palatal ridge, forming a V-shaped structure; caniniform process with an anterior edge that is set off from the palatal rim forming a notch; 'postcanine' teeth present on the maxilla; a ventrally directed transverse flange of the pterygoid with an obtuse posterior margin; a short interpterygoid vacuity that does not reach the level of the palatine pads; a dentary table that forms an elongate grooved surface on the dorsal surface of the dentary, bounded laterally by a low ridge and medially by a tall, thin, dorsally convex blade; 'postcanine' teeth present on the dentary blade; and the absence of a posterior dentary sulcus. A phylogenetic analysis confirms that P. dubei is a member of Pylaecephalidae, although we cannot corroborate that it is the sister taxon of Diictodon feliceps. The holotype of P. dubei was collected low in the Tapinocephalus Assemblage Zone in the northwestern Karoo Basin, near the contact between the Ecca and Beaufort groups, within the stratigraphic range of Robertia but above the ranges of Eodicynodon and Colobodectes. Ongoing research suggests dicynodonts in the Tapinocephalus Assemblage Zone appeared in sequence (Colobodectes first; Lanthanostegus, Robertia, Prosictodon second; Diictodon and Pristerodon third), in contrast to earlier works that portrayed Diictodon, Robertia, and Pristerodon as occurring throughout the zone.
... Toward the end of the Permian, in the Daptocephalus AZ, the number of cynodont genera had doubled. They comprise the Russian Dvinia, the more widely distributed Procynosuchus and the South African Cynosaurus and Nanictosaurus (Sues & Boy, 1988;Rubidge, 1995Rubidge, , 2005Abdala & Allison, 2005;Weide et al., 2010). These taxa have basal skull lengths (BSLs, measured from the anterior tip of the snout to the posterior end of the occipital condyles) ranging from 5.5 cm in Nanictosaurus to 14 cm in Procynosuchus. ...
... Until recently, the oldest known cynodont fossils were from the latest Permian (late Wuchiapingian-Changhsingian). They were represented in the Karoo Basin of South Africa, the Usili Formation of Tanzania, the upper Madumabisa Mudstone of Zambia, the fissure-fillings deposits of Upper Werra Clay near Korbach in Germany and the Sokolki locality on the northern Dvina River of Russia (Sues & Boy, 1988;Rubidge, 1995Rubidge, , 2005Abdala & Allison, 2005;Weide et al., 2010;Ivakhnenko, 2013). These cynodonts come from strata of the Daptocephalus AZ (formerly Dicynodon AZ) of the Karoo Basin and the Cistecephalus AZ of South Africa and the putative coeval faunas from Zambia and Tanzania (Angielczyk et al., 2014;Viglietti et al., 2015). ...
... In addition to being the largest therapsids from the Guadalupian, dinocephalians also represent the first occurrence of huge terrestrial tetrapods in Gondwana (Rubidge 1995(Rubidge , 2005. The overall body dimensions of Tapinocaninus show that the very large body size and mass of tapinocephalids was already established in the most basal member of the family. ...
... Regarding body size, dinocephalians are the largest Guadalupian therapsids and Tapinocaninus represents the earliest occurrence of huge terrestrial synapsids in Gondwana (Rubidge 1995(Rubidge , 2005. Amongst basal synapsids, large body size had already evolved in the 'pelycosaurs' during the late Early Permian and the early Middle Permian, especially amongst the large herbivorous members of the Family Caseidae (Olson 1968;Reisz 1986). ...
Dinocephalians were the earliest large terrestrial tetrapods from Gondwana, making this group crucial in understanding body mass (BM) evolution in basal synapsids, but no detailed weight determinations are available for the clade. Here we present the first BM estimate for a dinocephalian on the basis of the remarkably well preserved and complete skeleton of the basal tapinocephalid Tapinocaninus pamelae from the lowermost Beaufort Group of South Africa. We reconstructed three 3D models of Tapinocaninus using mounted skeletons of the dinocephalians Moschops and Ulemosaurus to reconstruct the missing elements. Applying a density range between 0.9 and 1.15 Kg/1000 cm3 for living tissue to the model we reconstructed an average BM of 892.63 Kg for the taxon. Classic regression formulae, based on humerus and femur circumference, provide higher values of 1694.5 Kg and 2015.8 Kg, with an overestimation of 90% and 126% respectively. The study confirms that volumetric BM estimates are more precise, and are recommended if relatively complete skeletons are available. The ‘intermediate’ posture recognized for Tapinocaninus, more upright with respect to the sprawling condition characterizing sphenacodontid ‘pelycosaurs’, could represent a response to a large BM, which, for the first time in synapsids, reaches weights close to a tonne.
... Dinocephalians were a diverse group of basal therapsids whose remains are known from the Ocher and Ischeevo deposits from the Kazanian of Cis-Uralian Russia (Tchudinov 1983), the Eodicynodon and Tapinocephalus Assemblage Zones (Beaufort Group) of South Africa (King 1988;Rubidge 1993;Modesto & Rybczynski 2000) and the Madumabisa Formation in Zimbabwe (Boonstra 1946;Lepper et al. 2000;Munyikwa 2001), as well as more recently from the Xidagou Formation at Dashankou, Yumen in western Gansu, China (Cheng & Ji 1996;Cheng & Li 1997), the Rio do Rasto Formation of the Paran a Basin in Brazil (Langer 2000;Cisneros et al. 2012), the Ruhuhu Formation of the Songea Group in Tanzania (Simon et al. 2010), and the Madumabisa Mudstone Formation of the Mid-Zambezi Basin in Zambia (Sidor et al. 2014). They were not only the largest therapsids from the Guadalupian but also the first large tetrapods to live on land in Gondwana (Rubidge 1995(Rubidge , 2005. Four dinocephalian families are recognized from the South African Karoo Supergroup (Anteosauridae, Titanosuchidae, Styracocephalidae and Tapinocephalidae) of which the Anteosauridae is considered the most basal and the Tapinocephalidae the most derived (Kammerer 2011), and Tapinocaninus in turn is considered to be a basal tapinocephalid (Rubidge 1991). ...
... Although the rocks of the Tapinocephalus Assemblage Zone of the lower Beaufort Group of South Africa have long been known to preserve the most diverse dinocephalian fauna (Boonstra 1969;Day 2013;Day et al. 2015), vertebrate fossils in the underlying Eodicynodon Assemblage Zone represent the first unambiguous evidence of a terrestrial environment in the southern Karoo Basin and the oldest evidence of synapsids from the southern hemisphere (Rubidge 1990(Rubidge , 1995(Rubidge , 2005. This fauna includes the relatively recently described dinocephalians Australosyodon (Rubidge 1994) and Tapinocaninus (Rubidge 1991). ...
Dinocephalians form an important component of the Guadalupian basal therapsid faunas of Pangaea. Most research undertaken on this clade has focused on the skull while postcranial research has lagged, largely because of the rarity of sufficiently complete specimens. The discovery of an almost complete skeleton of the basal tapinocephalid dinocephalian Tapinocaninus from the rocks of the lowermost Beaufort Group of South Africa for the first time provides an accurate vertebral count for a dinocephalian as well as morphological information on the appendicular skeleton. The long bones of Tapinocaninus pamelae are autapomorphic in several features within the dinocephalians, and the results enable discussion of some more general aspects of the appendicular skeleton of basal synapsids. Combined, the new data enable a new reconstruction of the posture of tapinocephalids. Although demonstrating several apomorphic characters, the skeleton retains pleisomorphic anatomical features previously known only in pelycosaur-grade synapsids, especially in the axial skeleton. The discovery greatly advances understanding of the postcranial morphology of tapinocephalid dinocephalians and will provide input on the enigmatic phylogenetic relationships of early therapsids.
... It also confirms that its presence in the northwest, lacking association with other dicynodonts, is a result of the exposure of older strata and that Colobodectes is biostratigraphically informative (sensu Angielczyk and Rubidge, 2009) rather than it being a result only of regional biogeography. Lastly, it is consistent with a northerly progradation of the shoreline during the Guadalupian, with the oldest recorded terrestrial deposits being limited to the southwestern part of the basin between Rietbron and Laingsburg (Rubidge, 2005;Rubidge et al., 2016). ...
... The rocks of the Beaufort Group preserve a largely continuous sedimentary record covering the period from the Middle Permian to the Middle Triassic (Hancox and Rubidge, 2001;Rubidge, 2005). The abundant tetrapod fossil record has allowed the establishment of seven assemblage zones with nine subzones (Smith et al., 2020). ...
Almost forty years of field investigations on the farm Lemoenfontein, near Aliwal North in the southern Free
State Province of South Africa, have recovered a diverse amniote fauna from rocks of the Burgersdorp Formation
that are assigned to the lower Middle Triassic Trirachodon-Kannemeyeria Subzone of the Cynognathus Assemblage
Zone (AZ). In total, 140 skulls and articulated skeletons of seven tetrapod taxa have been collected, along with
more recently collected details about their depositional environmental setting. Trace fossils including three
different burrow casts, each with distinctive geometries, were also collected and documented. The amniote
specimens include both juveniles and adults of the procolophonids Teratophon spinigenis and Thelephon contritus;
the rhynchosaur Eohyosaurus wolvaardti; bauriid therocephalian Microgomphodon oligocynus; and the cynodonts
Cricodon kannemeyeri and Trirachodon berryi. The diverse fauna is dominated by largely herbivorous tetrapods,
mainly procolophonids, all with dentitions adapted to browse fibrous plant material. The only carnivore present
is a small unidentified basal cynodont. Several of these tetrapods have previously been proposed as burrowers.
The diversity and abundance of well-preserved fossils provide new insight into how palaeoenvironmental and
behavioural factors contributed to the hyper-accumulation of tetrapod fossils at this site. Whilst the herbivorous
dicynodont Kannemeyeria simocephalus and carnivorous erythrosuchid archosaur Erythrosuchus africanus are
common components of the middle Cynognathus AZ Trirachodon-Kannemeyeria Subzone elsewhere in the basin,
they are absent from the lower exposures at Lemoenfontein, which suggests that the fossil assemblage represents
a transitional fauna from the Langbergia-Garjainia and Trirachodon-Kannemeyeria Subzones. Another interesting
aspect of the site is that all the tetrapod remains are of individuals of small body size. This apparent Lilliput effect
supports the view that the faunal recovery after the Permian-Triassic mass extinction in the Karoo Basin was only
fully developed by Middle Triassic times.
... The largest and most extensive of these was the main Karoo Basin, which is named after the semidesert region in the southern hinterland of South Africa. It formed to the north of the Cape Fold Belt, which borders the southern rim of the continent and is considered to be the source of much of the basin-fill's sedimentary rocks (Rubidge, 2005). Most workers interpret the Karoo Basin to be a foreland basin (Catuneanu et al., 1998(Catuneanu et al., , 2002Cole, 1992;Johnson, 1991;Johnson et al., 2006;Viglietti et al., 2017a), but alternative interpretations have been proposed Karoo Supergroup (Lindeque et al., 2011;Tankard et al., 2009Tankard et al., , 2012Turner, 1999;Turner & Thomson, 1998). ...
The Hofmeyr skull was discovered from the banks of the Vlekpoort RiverVlekpoort River, which traverses a broad plain northeast of the town of Hofmeyr, located in the hinterland of the Eastern Cape Province of South Africa. The fossil locality is directly underlain by the reddish siltstones of the Burgersdorp FormationBurgersdorp Formation, while the resistant sandstones of the overlying Molteno FormationMolteno Formation form the slopes of the Bamboesberg mountainsBamboesberg Mountains more than 10 km to the east. Both these formations accumulated through deposition by northwards-flowing rivers draining the Cape Fold BeltCape Fold Belt to the south, during the Triassic (251–201 Ma), filling the main Karoo BasinKaroo Basin, which was at that time situated in southern GondwanaGondwana. The modern landscape, dominated by the Great EscarpmentGreat Escarpment, was formed during a long, erosion-dominant period, which started right after GondwanaGondwana break-up, was accelerated during the predominant humid tropical climateClimate associated with the CretaceousCretaceous, and continues to this day. Short, steep south-flowing river systems, such as the Great Fish RiverGreat Fish River drainage, which encompass the Vlekpoort RiverVlekpoort River, drains the landscape across and south of the Great EscarpmentGreat Escarpment. QuaternaryQuaternary deposits drape the hill slopes and plain north of Hofmeyr. The Late Pleistocene age obtained from the Hofmeyr specimen overlaps with the fluvial record from central South Africa, which is a time when a dry climateClimate is assumed to have predominated over central South Africa. Locally the Vlekpoort RiverVlekpoort River valley is bounded by resistant KarooKaroo bedrock, with a prominent doleriteDolerite dyke approximately 4 km south of the fossil locality, one of several to intersect the modern landscape, controlling the local channel profile. Over the past century the construction of numerous dams and weirs in the river channel has interrupted the natural river evolution processes by raising the local base level, which has resulted in in the silting-up of the channel floor and the Hofmeyr fossil locality.
... As most previous work on the Burgersdorp Formation has been undertaken by palaeontologists, the vertebrate palaeontological signature of the formation is far better documented than its lithology. The fossil content of the Burgersdorp Formation comprises a rich and taxonomically diverse fauna of vertebrates, most notably tetrapods (e.g., temnospondyl amphibians, non-mammalian synapsids, parareptiles and archosaurs) as well as actinopterygian, sarcopterygian and chondrichthyan fish (Broom, 1909;Hutchinson, 1973;Hancox, 2003, 2004;Rubidge, 2005). Vertebrate trace fossils include numerous coprolites, well-preserved trirachodontid burrow casts (Groenewald et al., 2001), and scratch traces, interpreted as the claw-scratched ventral walls of a therapsid burrow system with a 3D network architecture (Bordy et al., 2019). ...
The subaerial unconformity that separates the Beaufort Group (Burgersdorp Formation) from the Stormberg Group (Molteno Formation) is currently the least documented and understood major stratigraphic contact within the fill of the main Karoo Basin of South Africa. The contact represents a major re-organisation of fluvial style, which is accompanied by a complete change in palaeontological representation as well. This work re-defines this contact and demonstrates that the aerial extent of the main Karoo Basin decreases from the Early to Middle Triassic, and that the stratigraphic gap represented by the Beaufort-Molteno contact merges cratonwards and represents at least the upper Anisian and Ladinian in the south of the basin, and the entire Middle Triassic in the north. This unconformity is preserved in every South-Central African Karoo aged basin and must represent a major change in Triassic basinal tectonics.
... As noted above, the type 536 locality of Jimusaria is problematic because of uncertainty surrounding its exact geographic 537 position and the fact that Cheng's (1986) reconstructed locality for the specimen is in an area that 538 has been faulted. The type locality of T. bogdaensis, which also has produced additional 539 specimens of Jimusaria, is located very close to our South Taodonggou locality (Sun, 1973b; The high abundance of the dicynodont Lystrosaurus in strata traditionally assigned to the 607 Lower Triassic in the Karoo Basin, and its biostratigraphic significance, have long been 608 recognized (e.g., Broom, 1906, Watson, 1914du Toit, 1918;Kitching, 1977;Groenewald and 609 Kitching, 1995;Lucas, 1998b;Rubidge, 2005 Permo-Triassic transition that is now geochronologically calibrated by a Bayesian age model. 667 ...
The Junggar and Turpan basins of Xinjiang Uygur Autonomous Region, northwest China, host a well-preserved terrestrial Permo-Triassic boundary sequence exposed along the northern and southern flanks of the Bogda Mountains. During the Permo-Triassic transition, this region was located in mid-latitude northeast Pangaea, making it an important comparison to the well-studied higher latitude record of the South African Karoo Basin. Broad similarities are apparent between the tetrapod fossil records of both areas, such as the reported co-occurrence of Dicynodon-grade dicynodontoids and Lystrosaurus in the upper Permian and the high abundance of Lystrosaurus in the Lower Triassic. However, the exact placement of the Permo-Triassic boundary in Xinjiang and South Africa has been debated. In the Chinese sections, the Permo-Triassic boundary falls within the upper Guodikeng Formation (= upper Wutonggou low order cycle), but several horizons have been proposed based on biostratigraphy, chemostratigraphy, and paleomagnetic data. A new Bayesian age model that is calibrated by multiple radiometric dates and tied to detailed litho- and cyclostratigraphic data offers new insight into the location of the Permo-Triassic boundary in Xinjiang and the opportunity to reconsider tetrapod occurrences in a highly resolved chronostratigraphic framework. We investigated the positions of new and historic tetrapod collections relative to the revised Permo-Triassic boundary, including uncertainties about the locations of key historic specimens. The stratigraphic range of Dicynodon-grade dicynodontoids in Xinjiang is poorly constrained: most specimens, including the holotype of Jimusaria sinkianensis, cannot be precisely placed relative to the Permo-Triassic boundary. A new specimen of Turfanodon sp. For which we have reliable data occurs in the upper Permian. Despite their previous treatment as Permian in age, most Bogda chroniosuchians were collected in strata above the Permo-Triassic boundary and the therocephalian Dalongkoua fuae also may be Triassic. Some prior placements of the Permo-Triassic boundary in Xinjiang imply an upper Permian lowest occurrence for the cosmopolitan dicynodont Lystrosaurus, but all Lystrosaurus specimens that we can precisely locate fall above the Permo-Triassic boundary. The high abundance of Lystrosaurus in the well-dated Early Triassic of Xinjiang suggests an Early Triassic age for the interval of greatest Lystrosaurus abundance in the Karoo Basin, where the exact ages of putative Permo-Triassic strata are more controversial. The Xinjiang record is an important datum for determining whether there was a single, globally synchronous time of highest Lystrosaurus abundance.
... Therocephalians are well represented in the fossil record of southern Pangea for most of the mid-Permian through mid-Triassic, and while species from China, Russia and other areas are scattered throughout much of the group's family tree, the Karoo Basin of South Africa is historically recognized as the group's center of sampled diversity (Lucas, 2002;Abdala et al., 2008;Huttenlocker, 2009;Ivakhnenko, 2011). For example, out of the 35 species of Permian therocephalians included in our phylogenetic analysis, 28 come from either the Karoo Basin or one of its related basins across southern Africa or Antarctica (Rubidge, 2005). However, among Triassic forms, only nine out of 17 species are from southern Pangea. ...
The Fremouw Formation (Transantarctic Basin) of Antarctica preserves an exceptional fossil record of tetrapods from the beginning of the Mesozoic at high paleolatitude. Many of these fossils can be identified to species that also occur in the much richer Lystrosaurus declivis Assemblage Zone of South Africa’s Karoo Basin, but endemic species also occur. A third category of Antarctic fossils includes those that can only be broadly classified or lack sufficient diagnostic features for a synapomorphy-based identification. Therocephalians are a prime example of the last category, with Akidognathidae indet., Baurioidea indet., and cf. Ericiolacerta parva, currently recognized from the lower Fremouw Formation. Here we describe the most complete skull for an Antarctic therocephalian discovered to date. Notictoides absens, gen. et sp. nov., preserves a unique dental formula, a large intranarial portion of the septomaxilla, two bony excrescences along the rostral margin of the lacrimal, and a complete secondary palate formed by the maxilla. These features, in combination with a sagittal crest with a slit-like parietal foramen, a long, low dentary, and reduced upper and lower antecanine tooth count, suggest a relatively derived position for N. absens within baurioids. Indeed, the results of an updated cladistic analysis unite N. absens with the clade including Nothogomphodon, Ordosiodon, and Bauriidae. More broadly, the discovery of a third endemic species in the Lower Triassic rocks of the Fremouw Formation suggests that diversification in the wake of the Permian–Triassic mass extinction was likely more geographically complex than currently appreciated.
... The boundary represents a change from marine to terrestrial facies and has long been interpreted as diachronous and to young from the southwest to the north based on sedimentology and biostratigraphy (Catuneanu et al., 2002;Rubidge, 2005;Rubidge et al., 1999). Here, the age of the boundary can be precisely calibrated. ...
Paleomagnetic results for a ∼2,353‐m‐thick magnetostratigraphic section for undeformed middle to late Permian rocks in the southeast of the Karoo Basin of South Africa are reported. Predominantly pseudo‐single‐domain or single‐domain titanomagnetite (with possible minor contributions by pyrrhotite and multi‐domain magnetite) were identified as remanence carriers of a dual polarity magnetization interpreted as the record of the Permian geomagnetic field during the Kiaman Reverse Polarity Superchron and subsequent Illawarra mixed polarity interval. The timing of remanence acquisition is further constrained by the effect of Jurassic‐aged dolerite intrusions, which either partially or wholly overprint the Permian remanence in their immediate vicinity. A paleopole at 62.0°S; 64.3°E and dp/dm = 4.9°/5.8° is calculated from the bedding‐corrected primary remanence (when corrected for inclination shallowing at f = 0.6 the paleopole is located at 53.2°S; 46.9°E and dp/dm = 5.9°/6.3°). This is comparable to other Permian paleopoles from the southwest section of the Karoo Basin. The end of the Kiaman Reverse Polarity Superchron can be correlated between the E‐W extremes of the basin to reveal a diachronous boundary between the Ecca and the Beaufort groups, with diachronicity calibrated to 1.1 million years for the first time.
... Karoo tetrapods extend from the Eodicynodon Assemblage Zone through the Triassic. The age of the Eodicynodon Assemblage Zone is difficult to assess (Rubidge et al., 2013); a late Roadian or early Wordian age has been suggested (Lucas, 2018), or it could occupy most of these two stages (Rubidge, 2005). Rubidge and Day (2020) suggested a Wordian age for the Eodicynodon Assemblage Zone but also accepted that it was more or less synchronous with the Ocher subassemblage and Mezen assemblage of Russia. ...
The youngest Paleozoic vertebrate-bearing continental deposits of North America are Middle Permian (Guadalupian) in age and occur in the Chickasha Formation (El Reno Group) of central Oklahoma and the lithostratigraphically lower San Angelo Formation (Pease River Group) of North-Central Texas. Although regarded originally as Guadalupian, these deposits have been assigned recently to the Early Permian on the basis of marine fossils and questionable lithostratigraphic extrapolations from marine to continental strata. A review of ammonoid genera recovered from the Blaine Formation, which overlies both the Chickasha and San Angelo in Oklahoma and Texas, shows that they range globally in age from the Early to Late Permian but most occur in the Guadalupian or Middle Permian. A modest but intensively studied paleobotanical record of compression fossils from the San Angelo, as well as palynomorphs in rocks associated with the Chickasha, presents an unquestionably Middle to Late Permian flora dominated by voltzian conifers. The Chickasha and San Angelo vertebrate assemblages are overwhelmingly dominated by large caseid synapsids and indicate a biostratigraphic signal of early Guadalupian. The occurrence of the tupilakosaurid temnospondyl Slaugenhopia, the parareptile Macroleter, and the eureptile Rothianiscus suggest a Roadian age (lowermost Guadalupian) given the global records of closely related forms. These plant and vertebrate assemblages contrast sharply with those of underlying Cisuralian rocks of the Hennessey Formation of Oklahoma and the Clear Fork Formation of Texas, both of which are much more fossiliferous than those of the Guadalupian in the region. A barren interval of up to 300 m in thickness separates these fossil-bearing intervals. This true void, first reported a half century ago by E.C. Olson, has not been recognized in recent biochronology studies. These findings, as well as those of other vertebrate paleontologists who have evaluated the San Angelo and Chickasha data by other means, strongly refute the notion of “Olson’s Gap” as currently entertained.
... Qualitative XRD was carried out on 33 samples with a Phillips PW 3830/40 Generator with PW 37010 mpd control using the X'pert data collector/identifier in the Africa (32°50'30.43"S,19°44'33.02"E). Rubidge, 2005 andSmithard et al., 2015). Radiometric dates are marked with black circles, shown in million years and taken from a: Bangert et al., 1999;b: Werner, 2006;c: Fildani et al., 2007. ...
Permian black shales from the lower Ecca Group of the southern main Karoo Basin (MKB) have a total organic carbon (TOC) of up to ~5 wt% and have been considered primary targets for a potential shale gas exploration in South Africa. This study investigates the influence of shale composition, porosity, pressure (P) and temperatures (T) on their geomechanical properties such as compressive strength and elastic moduli. On average, these lower Ecca Group shales contain a high proportion, ~50 to 70 vol%, of mechanically strong minerals (e.g., quartz, feldspar, pyrite), ~30 to 50 vol% of weak minerals (e.g., clay minerals, organic matter) and ~0 to 50 vol% of intermediate minerals (e.g., carbonates), which have highly variable mechanical strength. Constant strain rate, triaxial deformation tests (at T ≤100°C; P ≤50 MPa) were performed using a Paterson-type high pressure instrument. Results showed that the Prince Albert Formation is the strongest and most brittle unit in the lower Ecca Group in the southern MKB followed by the Collingham and then the Whitehill Formation. Compressive strength and Young’s moduli (E) increase with increasing hard mineral content and decrease with increasing mechanically weak minerals and porosity. On comparison with some international shales, for which compositional and geomechanical data were measured using similar techniques, the lower Ecca Group shales are found to be geomechanically stronger and more brittle. This research provides the foundation for future geomechanical and petrophysical investigations of these Permian Ecca black shales and their assessment as potential unconventional hydrocarbon reservoirs in the MKB.
... Very little palaeoentomological work has been conducted in the southern Karoo Basin (Geertsema et al. 2002;Prevec et al. 2010) despite ongoing and productive research in other palaeontological fields, particularly the study of vertebrate fossils (Rubidge 1995;Rubidge 2005;Ward et al. 2005;Botha & Smith 2006;Smith & Botha-Brink 2014;Day et al. 2015;Viglietti et al. 2016). Within this region, the Wapadsberg Pass area is renowned for its well-preserved vertebrate fossil assemblages that reflect changes in vertebrate diversity associated with the P-Tr extinction event (Ward et al. 2005;Botha & Smith 2006;Smith & Botha-Brink 2014). ...
The Permian–Triassic global crisis was the only event to have a dramatic impact on insect diversity, with Palaeozoic insect clades disappearing and accompanied by the accelerated rise of modern lineages. To date, most Permian palaeoentomological work has focused on the upper Permian deposits of the Normandien Formation (Beaufort Group), KwaZulu–Natal Province. This paper describes the regional insect fauna preserved close to the Permian–Triassic boundary at Wapadsberg Pass, southern Karoo Basin of South Africa, which provides a rare glimpse into insect life immediately before this global crisis. Here, we describe six insect species from six families within five orders from the two Wapadsberg Pass localities. Mioloptera stuckenbergi (Grylloblattodea) and Permocicada sp. (Hemiptera) were recorded previously from the Lopingian KwaZulu–Natal Province. In addition, we detail the first potential occurrence of South African Permian Tettigoniida (Orthoptera: Tettigonioidea & Hagloidea) and Anthracoptilidae (Paoliida). An Auchenorrhynchan (Hemiptera) nymph and an undetermined insect (order uncertain) also are described.
... Based on longer-distance correlation, we tentatively consider the type locality of Nshimbodon to come from upper Cistecephalus AZ-equivalent rocks. Future research on Madumabisa Mudstone Formation geology should add greater precision to its biostratigraphic subdivision and reassess the degree to which the AZs of South Africa's Main Karoo Basin show utility on a regional scale (Catuneanu et al., 2005;Rubidge, 2005). ...
Nonmammaliaform cynodonts were a diverse group of Permo-Triassic synapsids whose morphological evolution documented the beginning of many classic mammalian traits. Here, we describe a new basal cynodont from the upper Permian Madumabisa Mudstone Formation of Zambia’s Luangwa Basin as Nshimbodon muchingaensis gen. et sp. nov. The holotype, a relatively complete and undistorted cranium and articulated mandible with associated postcranial elements, is interpreted as the most complete and well-preserved example of a charassognathid cynodont, and preserves hitherto unknown details of charassognathid endocranial and postcranial anatomy. A phylogenetic analysis of 111 morphological characters from 25 therapsid taxa (including 15 Permo-Triassic cynodonts) supports a sister-taxon relationship between Nshimbodon and Abdalodon, including them with Charassognathus in a monophyletic Charassognathidae, and placing the family near the base of Cynodontia. In addition to its phylogenetic importance, Nshimbodon provides evidence of correlated transformations in the feeding system, neck, and shoulder, which are consistent with novel mammal-like locomotor and feeding mechanics in the earliest cynodonts. Lastly, given previous reports of charassognathids in the Karoo Basin of South Africa, the occurrence of Nshimbodon indicates that charassognathids, like the basal cynodont Procynosuchus, were geographically widespread in southern Pangea by Lopingian times. Continued collecting in the Madumabisa Mudstone Formation will lead to a better understanding of the formation’s Permian cynodont diversity and biostratigraphy, as well as the biogeographic structure of southern Pangean vertebrate assemblages prior to the Permo-Triassic mass extinction.
http://zoobank.org/urn:lsid:zoobank.org:pub:143CE9D3-5742-4E92-B48F-164685F0907C
... The Langbergia-Garjainia Subzone (= subzone A) has typically been considered late Early Triassic (Olenekian) in age, whereas the Trirachodon-Kannemeyeria and Cricodon-Ufudocyclops Subzones (= subzones B and C) are usually considered to represent the early Middle Triassic (Anisian-early Ladinian) (Hancox, 2000;Kammerer et al., 2018;Wynd et al., 2018;Hancox et al., 2020; though see Ottone et al., 2014 for a radiometric date from the Puesto Viejo Group in Argentina suggesting that the uppermost portions of the Cricodon-Ufudocyclops Subzone could be as young as Carnian). The subzones differ in the presence and diversity of kannemeyeriiform taxa as well, with none present in the Langbergia-Garjainia Subzone (= subzone A); only Kannemeyeria simocephalus known from the Trirachodon-Kannemeyeria Subzone (= subzone B); and Ufudocyclops and Shansiodon present in the Cricodon-Ufudocyclops Subzone (= subzone C) (Hancox et al., 1995(Hancox et al., , 2013Rubidge, 2005;Kammerer et al., 2019). Since the recognition of a three-fold division within the Cynognathus AZ, there has been disagreement as to which subzone provides the best correlation to the upper Fremouw assemblage, with Sidor et al. (2007) suggesting the Langbergia-Garjainia Subzone (= subzone A), Abdala et al. (2005) and Hancox et al. (2020) suggesting the Trirachodon-Kannemeyeria Subzone (= subzone B), and Fröbisch (2009) suggesting the Trirachodon-Kannemeyeria and Cricodon-Ufudocyclops Subzones (= subzones B and C). ...
A kannemeyeriiform dicynodont is described on the basis of an occipital plate from the upper Fremouw Formation (Middle Triassic) Gordon Valley locality in the Beardmore Glacier region of Antarctica. The Antarctic specimen is comparable in size to Kannemeyeria simocephalus from the well-known Cynognathus Assemblage Zone of the Beaufort Group of South Africa, and represents the largest therapsid currently known from the upper Fremouw Formation. The presence of an occipital condyle with distinct contributions from the exoccipital and the basioccipital; a wide, tri-radiate occipital condyle; and a well-developed tympanic process of the paroccipital, which is situated below the level of the occipital condyle, represent a combination of character states hitherto unknown among Kannemeyeriiformes. Combined with the possible autapomorphic feature of slender, dorsoventrally elongate basal tubera, this may suggest the Antarctic specimen represents a new kannemeyeriiform taxon. This specimen represents the most complete, and only the fourth definitive, dicynodont specimen known from the upper Fremouw Formation, and the contradictory phylogenetic character data from these specimens adds support for the presence of multiple (at least two) kannemeyeriiform taxa within the upper Fremouw tetrapod assemblage. Taken together, these kannemeyeriiform specimens provide additional support for a correlation with the Cynognathus Assemblage Zone, particularly the Trirachodon-Kannemeyeria or Cricodon-Ufudocyclops subzones (= subzones B or C), as well as an Anisian or younger age for the upper Fremouw tetrapod fauna.
... Based on its fauna, Lucas (1998) ascribed the Heshanggou Formation to the Lootsbergian land-vertebrate faunachron, correlated to the Lystrosaurus Assemblage Zone of the Karoo Basin, thus confirming an Early Triassic age for the unit. According to Rubidge (2005), the age of Xilousuchus sapingensis and its associated vertebrate fauna must be older than early Anisian, thus further constraining the Heshanggou Formation to an Olenekian age (see also Nesbitt et al., 2010a). ...
The Permian-Triassic mass extinction (PTME, ca. 252 Mya) was one of the most severe biotic crises of the Phanerozoic, eliminating > 90% of marine and terrestrial species. This was followed by a long period of recovery in the Early and Middle Triassic which revolutionised the structure of both marine and terrestrial ecosystems, triggering the new ecosystem structure of the Mesozoic and Cenozoic. Entire new clades emerged after the mass extinction, including decapods and marine reptiles in the oceans and new tetrapods on land. In both marine and terrestrial ecosystems, the recovery is interpreted as stepwise and slow, from a combination of continuing environmental perturbations and complex multilevel interaction between species in the new environments as ecosystems reconstructed themselves. Here, we present a review of Early Triassic terrestrial tetrapod faunas, geological formations and outcrops around the world, and provide a semi-quantitative analysis of a data set of Early Triassic terrestrial tetrapods. We identify a marked regionalisation of Early Triassic terrestrial tetrapods, with faunas varying in both taxonomic composition and relative abundance according to palaeolatitudinal belt. We reject the alleged uniformity of faunas around Pangaea suggested in the literature as a result of the hothouse climate. In addition, we can restrict the-tetrapod gap‖ of terrestrial life in the Early Triassic to palaeolatitudes between 15°N and about 31°S, in contrast to the earlier suggestion of total absence of tetrapod taxa between 30°N and 40°S. There was fairly strong provincialism following the PTME, according to cluster analysis of a taxon presence matrix, entirely consistent with Early Triassic palaeobiogeography. Unexpectedly, the overall pattern for Early Triassic terrestrial tetrapod faunas largely reflects that of the Late Permian, suggesting that the recovery faunas in the Early Triassic retained some kind of imprint of tetrapod distributions according to palaeogeography and palaeoclimate, despite the near-total extinction of life through the PTME.
... This glacial succession is overlain by the Beaufort Group, which is dominated by aggradational floodplain deposits (Smith et al. 1993) and subdivided into the Abrahamskraal, Middleton, Balfour, Katberg, and Burgersdorp formations (Fig. 1). Due to the homogeneity of lithologies and, until recently, a dearth of geochronometric or paleomagnetic data on which to subdivide the succession, changes in vertebrate biostratigraphy have been used to correlate deposits across the basin (Rubidge 1995(Rubidge , 2005. The upper member of the Balfour Formation, the Palingkloof Member, is reported to span the vertebratedefined Permian-Triassic Boundary (PTB), whereas the overlying Katberg Formation is considered Lower Triassic ( Fig. 1; Smith and Botha-Brink 2014). ...
The fully continental succession of the Beaufort Group, Karoo Basin, South Africa, has been used in the development of environmental models proposed for the interval that spans the contact between the Daptocephalus to Lystrosaurus Assemblage Zones, associated by some workers with the end-Permian extinction event. An aridification trend is widely accepted, yet geochemical data indicate that the majority of in situ paleosols encountered in this interval developed in waterlogged environments. To date, the presence of calcic paleosols in the latest Permian can be inferred only from the presence of calcite-cemented pedogenic nodules concentrated in fluvial channel-lag deposits. Here, we report on the first empirical evidence of in situ calcic Vertisols found in the upper Daptocephalus Assemblage Zone near Old Wapadsberg Pass, one of eight classic localities in which the vertebrate turnover is reported in the Karoo Basin. Seven discrete intervals of calcic Vertisols, exposed over a very limited lateral extent, occur in an ∼ 25 m stratigraphic interval. Estimates of mean annual temperature and mean annual precipitation are calculated from geochemical measurements of one paleosol, and these estimates indicate that the prevailing climate at the time of pedogenesis was seasonally cold and humid. Correlation with adjacent stratigraphic sections indicates that the late Permian landscape experienced poorly drained and better-drained phases, interpreted to reflect a climate that varied between episodically dry and episodically wet. In contrast to a paleoenvironmental reconstruction of unidirectional aridification from strata in the Wapadsberg Pass region, this study provides new evidence for a wetting trend towards the Daptocephalus–Lystrosaurus Assemblage-Zone boundary.
... Recent research has demonstrated the importance of Karoo fossils for global stratigraphic correlation and for the conceptualization of basin development models (e.g., Catuneanu, Hancox, and Rubidge 1998;Hancox 1998;Neveling 2002;Rubidge 2005). The discovery of datable ash beds that can be linked to biozone-defining fossils has considerably enhanced research possibilities by providing high-resolution radiometric ages for the Permian biozones (Rubidge et al. 2013;Day et al. 2015;Gastaldo et al. 2015Gastaldo et al. , 2020, and thus opening up a way to ascertain rates of evolution in fossil tetrapod lineages (Roopnarine et al. 2017) , as well as the timing and duration of extinction events (e.g. ...
... By comparison with the Russian therapsid fauna of the Ocher complex, the age of the Eodicynodon Assemblage Zone is considered to be Wordian (Rubidge, 2005). Radiometric dates from the Karoo have not yet provided constraints on the age of the Eodicynodon Assemblage Zone. ...
The 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.
... Based on these new age assessments, time-equivalent stratigraphic units of the MAZ (though usually lacking shared index taxa) could include: McCoy Brook Formation and Newark Basin, Canada (Fedak et al., 2015); Portland Formation, Hartford Rift Basin (Hubert et al., 1992) (Rubidge, 2005;Smith et al., 2007Smith et al., , 2012Bomfleur et al., 2011;Sciscio et al., 2017a). ...
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 first 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 reflect effects of the end-Triassic extinction event (ETE).
... This is one of the oldest therapsid assemblages of the world. The age of the fauna is regarded as Roadian (Liu et al., 2009) or Wordian (Olroyd and Sidor, 2017;Rubidge, 2005), older than 266 Ma. ...
... The most important Middle Triassic vertebrate yielding horizon in Gondwana is the Manda Formation of Tanzania (Cox, 1991;Lucas, 1998); it has produced a large number of Middle Triassic vertebrates. The other horizons are the Omingonde Formation of Namibia (Keyser, 1973;Pickford, 1995;Abdala and Smith, 2009), the N'tawere Formation of Zambia (Catuneanu et al., 2005;Rubidge, 2015), the Arcadia Formation, and the Hawkesbury and Wianamatta formations of Australia (Banks, 1978;Warren, 2012). Jain et al. (1964) considered the age of Yerrapalli Formation as late Early Triassic or possibly early Middle Triassic. ...
... Por el contrario, el sector inferior de la Fm. Elliot, de edad equivalente, registra dinosaurios sauropodomorfos y terápsidos, sumando en los sectores superiores de la formación, el registro de pseudosuquios crocodilomorfos y dinosaurios terópodos (Rubidge, 2005) (Fig. 3). ...
... The Karoo-aged basins of southern and eastern Africa have provided fossils of critical importance in shaping our understanding of Permo-Triassic vertebrate evolution, shedding light on the emergence of crocodiles, dinosaurs, mammals and turtles, among many other groups (Kitching and Raath, 1984;Rubidge, 2005). Most of this material has been collected from within the main Karoo Basin, but important collections have also been made in other areas, including the Ruhuhu Basin of Tanzania and the Luangwa Basin of Zambia (e.g., Sidor and Nesbitt, 2018). ...
Correlations between continental sequences within the Karoo-aged basins of southern and eastern Africa are difficult due to the dearth of shared index fossils and a lack of radioisotopic dates for key formations. Here we describe four sites along the southeastern shoreline of Lake Kariba, Zimbabwe, within the Mid-Zambezi Basin, that yield material of phytosaurs (Archosauromorpha: Phytosauria) from within the informal Tashinga Formation (Upper Karoo Group). These phytosaur remains are the first to be recovered from sub-Saharan mainland Africa, representing a major geographic range extension for this group into high southern latitudes. Furthermore, an LA-ICPMS maximum depositional age of 209.2 ± 4.5 Ma (late Norian/early Rhaetian) derived from detrital zircons provides the first absolute age estimate for any of these sites. The phytosaurs are associated with lungfish and metoposaurid amphibians, forming part of a terrestrial-aquatic dominated biota, a previously undocumented biome from the Late Triassic of southern Africa.
... However, individual pareiasaur specimens from the Tapinocephalus AZ cannot currently be securely identified based on the current diagnoses, descriptions and literature, with the result that most specimens recovered have historically been, and continue to be, assigned to the genus Bradysaurus as a waste-basket taxon. This hampers our understanding of Middle Permian biodiversity (Rubidge, 2005;Nicolas, 2007;Van der Walt et al., 2011;Day, 2013;Rubidge et al., 2013Rubidge et al., , 2016Day et al., 2015). The Lower Beaufort fossil record contains evidence of an extinction event on land at the end of the Capitanian (Guadalupian), and the main victims were dinocephalian therapsids and pareiasaurs (Day, 2013;Day et al., 2015). ...
Pareiasaurs were globally distributed, abundant, herbivorous parareptiles of the Middle to Late Permian, with the basal-most members found in the Middle Permian of South Africa. These basal taxa were particularly abundant and went extinct at the end of the Gaudalupian (Capitanian) at the top of the Tapinocephalus Assemblage Zone. Currently four taxa are recognized in this group: Bradysaurus seeleyi, B. baini, Nochelesaurus alexanderi and Embrithosaurus schwarzi, but they are all poorly understood. We here present the first detailed cranial description and updated diagnosis for Embrithosaurus schwarzi. No cranial autapomorphies were identified. However, Embrithosaurus schwarzi is a distinct taxon in this group, based on its unique dentition and using a combination of cranial features. It has nine marginal cusps on all maxillary and mandibular teeth, and wider maxillary teeth than in the co-occurring taxa, due to the marginal cusps being arranged more regularly around the crown, and the apex of the crown lacking the long, central, three-cusped trident. Our updated phylogenetic analysis recovers the four Middle Permian South African taxa as a monophyletic group for the first time, which we call Bradysauria, comprising a clade including Embrithosaurus, Bradysaurus baini and a polytomy including Nochelesaurus and Bradysaurus seeleyi.
... Although tooth assemblages are rare in Middle Triassic terrestrial strata, recent fieldwork (2007,2008,2012,2015,2017) in the Manda Beds of the Ruhuhu Basin, Tanzania (Sidor & Nesbitt, 2017), has revealed a rich assemblage of archosauriforms known from postcrania and partial crania, including teeth ( Nesbitt et al., 2010Nesbitt et al., , 2014Smith et al., 2018). Specifically, these teeth come from the middle and upper Lifua Member bone accumulations ( Smith et al., 2018), except one tooth (NMT RB831) which comes from the lower bone accumulation (Nesbitt et al., 2017;Smith et al., 2018), which are thought to be Anisian in age (Rubidge, 2005) but may be as young as early Carnian ( Ottone et al., 2014;Marsicano et al., 2016;Peecook et al., 2018;Wynd et al., 2018). If the Anisian age is correct, then this is one of the oldest diverse archosauriform faunas known that is also represented by specimens from historical collections (Butler et al., 2010(Butler et al., , 2018Nesbitt et al., 2010Nesbitt et al., , 2013Nesbitt et al., , 2014Nesbitt et al., , 2017Barrett, Nesbitt & Peecook, 2015). ...
Following the Permo–Triassic mass extinction, Archosauriformes—the clade that includes crocodylians, birds, and their extinct relatives outside crown Archosauria—rapidly diversified into many distinct lineages, became distributed globally, and, by the Late Triassic, filled a wide array of resource zones. Current scenarios of archosauriform evolution are ambiguous with respect to whether their taxonomic diversification in the Early–Middle Triassic coincided with the initial evolution of dietary specializations that were present by the Late Triassic or if their ecological disparity arose sometime after lineage diversification. Late Triassic archosauriform dietary specialization is recorded by morphological divergence from the plesiomorphic archosauriform tooth condition (laterally-compressed crowns with serrated carinae and a generally triangular lateral profile). Unfortunately, the roots of this diversification are poorly documented, with few known Early–Middle Triassic tooth assemblages, limiting characterizations of morphological diversity during this critical, early period in archosaur evolution. Recent fieldwork (2007–2017) in the Middle Triassic Manda Beds of the Ruhuhu Basin, Tanzania, recovered a tooth assemblage that provides a window into this poorly sampled interval. To investigate the taxonomic composition of that collection, we built a dataset of continuous quantitative and discrete morphological characters based on in situ teeth of known taxonomic status (e.g., Nundasuchus , Parringtonia : N = 65) and a sample of isolated teeth ( N = 31). Using crown heights from known taxa to predict tooth base ratio (= base length/width), we created a quantitative morphospace for the tooth assemblage. The majority of isolated, unassigned teeth fall within a region of morphospace shared by several taxa from the Manda Beds (e.g., Nundasuchus , Parringtonia ); two isolated teeth fall exclusively within a “ Pallisteria ” morphospace. A non-metric multidimensional scaling ordination ( N = 67) of 11 binary characters reduced overlap between species. The majority of the isolated teeth from the Manda assemblage fall within the Nundasuchus morphospace. This indicates these teeth are plesiomorphic for archosauriforms as Nundasuchus exhibits the predicted plesiomorphic condition of archosauriform teeth. Our model shows that the conservative tooth morphologies of archosauriforms can be differentiated and assigned to species and/or genus, rendering the model useful for identifying isolated teeth. The large overlap in tooth shape among the species present and their overall similarity indicates that dietary specialization lagged behind species diversification in archosauriforms from the Manda Beds, a pattern predicted by Simpson’s “adaptive zones” model. Although applied to a single geographic region, our methods offer a promising means to reconstruct ecological radiations and are readily transferable across a broad range of vertebrate taxa throughout Earth history.
... These fossils reveal that the upper Tapinocephalus and/or Pristerognathus Assemblage Zones are present in the Koonap Formation in the study area. The presence of fossils of the Tapinocephalus Assemblage Zone in the lower Koonap Formation, and the absence of Eodicynodon, implies that the Ecca-Beaufort contact youngs towards the northeast and reflects a northeasterly prograding shoreline in response to tectonic development, as previously documented for the basin (Rubidge et al., 2000;Rubidge, 2005). ...
Rocks of the Late Carboniferous to Early Jurassic aged Karoo Supergroup of South Africa preserve a sedimentary succession, deposited in a retro-arc foreland setting. This succession documents environmental change from glacial-marine, through full marine to continental fluvial and aeolian environments, culminating in rift associated continental flood basalt extrusions. The Karoo Basin is internationally renowned for its wealth of fossil tetrapods, enabling the establishment of a reliable and useful biostratigraphic framework which has international applicability for correlation of Permian-Triassic tetrapod-bearing continental deposits. The transition from marine to continental deposition in the Karoo has been the subject of much recent research, particularly in regard to the position of the Ecca-Beaufort contact. Our study indicates for the first time that in the south-eastern part of the basin, as for the rest of the basin, this transition comprises three separate facies associations deposited respectively in the prodelta, subaqueous delta plain and subaerial delta plain environments. The Tapinocephalus Assemblage Zone is the lowermost vertebrate biozone in the Koonap Formation indicating that the Ecca-Beaufort boundary is diachronous in the southern part of the basin, younging towards the east. This supports the easterly to northeasterly prograding shoreline model previously proposed for the Ecca-Beaufort transition and provides new insight on the distribution of the earliest land-living vertebrates in the south-eastern Karoo Basin.
... (B) Stratigraphic distribution of Diademodontidae (in yellow) and Trirachodontidae (in blue-purple), with Diademodon in pale yellow, Titanogomphodon in dark yellow, Langbergia in pale blue, Cricodon in blue sky, Trirachodon in dark blue, Sinognathus in light purple and Beishanodon in dark purple. Stratigraphic extension of geological units based on Liu, Ramezani & Li (2018) for the Ermaying Formation, Gao et al. (2010) and Niu et al. (2018) for the Hongyanjing Formation, Rubidge (2005) for the Cynognathus Assemblage Zone, Wynd et al. (2018) for the Manda Beds and the Upper Omingonde, Ntawere and Fremouw formations, and Ottone et al. (2014) for the Río Seco de la Quebrada Formation. Stars denote the U-PB geochronologic ages of 243.53 Ma from Liu, Ramezani & Li (2018) for the upper Ermaying Formation in China, and 235.82 ...
Gomphodont cynodonts were close relatives of mammals and one of the Mesozoic lineages of cynodont therapsids that became extinct at the end of the Triassic. Gomphodonts were omnivorous to herbivorous animals characterized by labiolingually expanded postcanines, which allowed tooth-to-tooth occlusion. The morphology of the upper and lower postcanines presents important means of distinguishing among major lineages within Gomphodontia, that is, Diademodontidae, Trirachodontidae, and Traversodontidae, but the dentition of most Diademodontidae and Trirachodontidae remain poorly documented. Here, we present a comprehensive description of the dentition of each diademodontid and trirachodontid species, as well as detailed illustrations of each dental unit, after firsthand examination of material and 3D reconstructions of postcanine teeth. Based on dental morphology, Trirachodon berryi and "Trirachodon kannemeyeri," considered as separate taxa by some authors are here interpreted as representing different ontogenetic stages of the same species. Likewise, Sinognathus and Beishanodon, thought to belong to non-cynognathian cynodonts and traversodontids by some authors, are referred to Trirachodontidae and Gomphodontia based on dental characters, respectively. Finally, we propose a standardized list of terms and abbreviations for incisors, canines, and postcanines anatomical entities, with the goal of facilitating future descriptions and communication between researchers studying the gomphodont dentition. Subjects Evolutionary Studies, Paleontology
... Records from northern Africa are critical to answering this question, yet remain relatively poorly known in comparison to elsewhere across the continent and Gondwana as a whole (Fig. 1). In particular, the extensive Mesozoic sedimentary strata of Ethiopia are well-positioned to help address the biogeographic effects of the break-up of Pangaea, but the vertebrate fossil assemblages from these units are not well sampled compared to other African faunas, such as the Triassic-Jurassic of southern Africa (e.g., Olsen and Galton, 1984;Knoll, 2004Knoll, , 2005Rubidge, 2005;Sidor et al., 2013) and Morocco (e.g., Dutuit, 1976;Jalil, 1999;Jalil and Peyer, 2007;Tourani et al., 2000;Allain and Aquesbi, 2008;Allain et al., 2004Allain et al., , 2007Kammerer et al., 2012), and the Late Jurassic of Tendaguru, Tanzania (e.g., Janensch, 1914Janensch, , 19221961;Russell et al., 1980;Galton, 1988;Heinrich, 1991Heinrich, , 1998, 2001Heinrich et al., 2001;Aberhan et al., 2002;Arratia et al., 2002;Remes, 2007Remes, , 2009Mannion et al., 2019). This under-sampled "African Gap" (O' Connor et al., 2006;Roberts et al., 2010) is vital for a comprehensive understanding of Mesozoic Pangaea because this area is near the actively rifting Gondwana-Laurasia margin in the Tethys, and records warm and semi-arid low-paleolatitude regions in a hothouse world (cf. ...
Ethiopia preserves extensive Mesozoic non-marine sedimentary sequences, but dinosaur fossils are exceptionally rare. The record is limited to a handful of theropod and ornithischian teeth from the Upper Jurassic Mugher Mudstone of the eastern margin of the Northwest Plateau, which has otherwise produced a diverse vertebrate fossil assemblage including actinopterygians, dipnoans, testudineans, crocodyliforms, and mammaliaforms. Here, we report the discovery of the first confirmed sauropod dinosaur from Ethiopia. The tooth BST VP-1/1 comes from a fine-to medium-grained, pebble and clast-rich zone with concentrated lenses of vertebrate microfossils in the lower part of the Mugher Mudstone. BST VP-1/1 is broad crowned, complete to the root, and slightly ellipsoidal midway in cross-section proximally toward the root. The distal half of the tooth has a chisel like appearance. BST VP-1/1 is planar lingually, convex labially, and narrows apically. These features compare closely with those of early macronarians, such as Giraffatitan brancai from the penecontemporaneous Tendaguru Formation in Tanzania. This specimen demonstrates the presence of sauropods in Ethiopia for the first time, and indicates that macronarians were widespread in East Africa during the Late Jurassic Epoch.
... Early burnetiamorphs coexisted with tapinocephalids but were much smaller in body size (Rubidge and Sidor 2001). The diverse but relatively shortlived tapinocephalid clade is restricted to the Guadalupian (~260 Ma; middle Permian, Barghusen, 1975;Rubidge, 2005;Kammerer, 2009;Olroyd & Sidor, 2017), whereas burnetiamorphs persisted until the end of the Permian, with 11 genera currently recognized (Day et al. 2018). Importantly, burnetiamorphs developed a wide range of bony adornments on their skulls, including crests, bosses, and dome-like thickenings, which can be tied to their relatively speciose fossil record (Padian & Horner, 2011;Sidor et al. 2017). ...
Thickened, pachyostotic skulls are best known in pachycephalosaur dinosaurs, but evolved convergently in Permian burnetiamorphs as well as in some other stem‐mammal groups and Triassic archosauromorphs. Until now, only pachycephalosaur domes have been histologically sampled to reveal patterns of bone tissue microstructure and growth. Using computed tomography and osteohistology, we serially thin‐sectioned one of the smallest burnetiamorph skull caps ever recovered (estimated skull length = 10 cm), as well as an individual nearly twice as large, and here report the first cranial histological data from this clade. We recognize four highly vascularized histological zones visible in coronal thin‐sections, only one of which shares morphological similarities with the tripartite zonation previously reported in pachycephalosaur domes. Zone A forms the endocranial region of the skull cap and records disorganized primary osteons in a fibrolamellar complex. Zone B preserves a border of compact, avascular layers of parallel‐fibered bone surrounding an interior of partially remodeled vascular canals. Interestingly, the outline of Zone B resembles the shape of an incipient skull roof. Zone C forms the thickest portion of the skull cap and is composed of fast‐growing woven bone with minimal osteonal development. The superficial Zone D has a matrix of predominantly woven bone with narrower primary vascular canals than in deeper regions of the skull caps. Unlike in pachycephalosaurs, where primary vascular porosity is thought to decrease through ontogeny, both burnetiamorph skull caps preserve a thick Zone C of highly vascularized tissue. Additionally, the remnants of sutures are visible as radial struts that taper superficially, leaving no trace on the surface of the skull. Even in the smallest individual, the sutures are closed ectocranially, which is unusual, given that some large, presumably adult pachycephalosaur domes preserve open sutural gaps. Although pachycephalosaur and burnetiamorph skull domes are superficially similar, histological analysis reveals differences in their vascularity and construction that imply multiple evolutionary pathways to form an elaborate pachyostotic dome.
... However representatives are also known from the Madumabisa Formation in Zimbabwe (Boonstra, 1946;Lepper et al., 2000;Munyikwa, 2001), the Ruhuhu Formation of the Songea Group in Tanzania (Simon et al., 2010), the Madumabisa Mudstone Formation of the Mid Zambezi Basin in Zambia (Sidor et al., 2014), the Rio do Rasto Formation of the Paraná Basin in Brazil (Cisneros et al., 2012;Langer, 2000), the Ocher and Ischeevo deposits from the Kazanian of Cis-Uralian Russia (Tchudinov, 1983) and from the Xidagou Formation at Dashankou, Yumen in western Gansu, China (Cheng and Ji, 1996;Cheng and Li, 1997). In addition to being the largest therapsids from the Guadalupian, dinocephalians were also the first large tetrapods to live on land in Gondwana (Rubidge, 1995(Rubidge, , 2005Rubidge et al., 2019), shedding light on the early evolution of gigantic body masses in basal synapsids. ...
... Although tooth assemblages are rare in Middle Triassic terrestrial strata, recent fieldwork (2007,2008,2012,2015,2017) in the Manda Beds of the Ruhuhu Basin, Tanzania (Sidor & Nesbitt, 2017), has revealed a rich assemblage of archosauriforms known from postcrania and partial crania, including teeth (Nesbitt et al., 2010(Nesbitt et al., , 2014Smith et al., 2018). Specifically, these teeth come from the middle and upper Lifua Member bone accumulations (Smith et al., 2018), except one tooth (NMT RB831) which comes from the lower bone accumulation (Nesbitt et al., 2017;Smith et al., 2018), which are thought to be Anisian in age (Rubidge, 2005) but may be as young as early Carnian (Ottone et al., 2014;Marsicano et al., 2016;Peecook et al., 2018;Wynd et al., 2018). If the Anisian age is correct, then this is one of the oldest diverse archosauriform faunas known that is also represented by specimens from historical collections (Butler et al., 2010(Butler et al., , 2018Nesbitt et al., 2010Nesbitt et al., , 2013Nesbitt et al., , 2014Nesbitt et al., , 2017Barrett, Nesbitt & Peecook, 2015). ...
Mass extinctions provide a biological “reset” often linked to subsequent biological radiations, generating a repeated macroevolutionary pattern. The End-Permian Mass Extinction, largest of the “Big Five,” decimated ecosystems and environments. Following the extinction, archosaurs (group including birds, crocodylians, and their extinct relatives) rapidly evolved into numerous distinct species, expanded globally, and, by the Late Triassic, had filled a wide array of niches. It is unclear if the species diversification of archosaurs in the Early and Middle Triassic was co-incident with the ecological specializations present by the Late Triassic, or if ecological disparity occurred after lineage splitting. One measure of ecology in the fossil record is teeth which have a direct link to ecology through diet, although Early and Middle Triassic tooth assemblages are rare, limiting utilization of tooth morphology during this critical time. However, recent fieldwork (2007, 2017) in the Middle Triassic Manda Beds of the Ruhuhu Basin, Tanzania has revealed a tooth assemblage that partially fills this gap. To reconstruct the species composition of the assemblage we used teeth within jaws of known taxonomic assignment (e.g., Nundasuchus, Parringtonia, and one undescribed species) and expanded with 31 isolated teeth of unknown species affiliation. We analyzed this dataset using both continuous measurements (PCA) and discrete tooth characters (non-metric multidimensional scaling, NMDS) using the softwares R and PAST. Continuous measurements (observations = 71) produced a linear relationship of tooth height predicting tooth base ratio (=base length/base width). Using this relationship we generated a morphospace in which the majority of isolated teeth fell within a zone of overlap shared by several Manda species (four of five taxa). Several isolated teeth fall outside of the known taxa morphospace and two teeth fall exclusively within the space of Pallisteria though this may be the result of size. The discrete NMDS method (observations = 67) of eleven binary characters removed the potential influence of size and reduces overlap among species (significant overlap in two of five taxa). The majority of the isolated teeth fall within the Nundasuchus morphospace and two are within Pallisteria morphospace. The significant overlap of tooth shape among species and overall similarities indicate that ecological diversification lagged behind species diversification in archosaurs, a pattern predicted in Simpson’s 1944 “adaptive zones” model. Though this represents a single locality, the methods used herein offer a promising lens to reconstructing ecological radiations and are readily transferable across a broad range of Earth history.
... yuani [¼ 'Chasmatosaurus' yuani]) and a newly defined monophyletic Prolacertidae to consist of Prolacerta broomi from South Africa and Antarctica and Kadimakara australiensis from Australia (Bartholomai, 1979;Colbert, 1987: Ezcurra andButler, 2015). Importantly, the taxa remaining in the taxonomically updated Proterosuchidae are from strata associated with the Permo-Triassic boundary in the uppermost Permian (Vyazniki Biotic Assemblage of Russia) and lowermost Triassic (Palingkloof Member of the Balfour Formation of South Africa, Jiucaiyuan Formation of China; Golubev, 2000;Lucas, 2001;Rubidge, 2005;Nesbitt et al., 2015), indicating that the absence of a Proterosuchus-like taxon from well-sampled lower Fremouw localities is unsurprising given its likely correlation with the portion of the LAZ tens of meters above the PTB (see below). Ezcurra (2016) found Early Triassic taxa that had been previously considered 'proterosuchian' in different positions relative to the newly defined Proterosuchidae: Tasmaniosaurus triassicus from Australia was found as sister to Archosauriformes, whereas Kalisuchus rewanensis from Australia and Chasmatosuchus (C. ...
Triassic-aged fossil vertebrates have been sporadically collected from the Fremouw Formation, central Transantarctic Mountains, since their initial discovery in the late 1960s, giving paleontologists insight into high-latitude faunas in the wake of the end-Permian mass extinction event. On a recent expedition (2010–2011), a small reptile skeleton was collected from Graphite Peak, which we present here alongside novel geological data and interpretations taken on site. Antarctanax shackletoni, gen. et sp. nov., is known from a partial postcranial skeleton including cervical and dorsal vertebrae, a humerus, and both pedes. Important morphological information includes well-defined laminae and deep fossae on cervicodorsal vertebrae. The new taxon can be differentiated from previously known Fremouw Formation reptiles (e.g., Prolacerta, Procolophon), as well as those from the Karoo Basin, South Africa (e.g., Mesosuchus, Proterosuchus, Euparkeria). Our inclusion of A. shackletoni in phylogenetic analyses of early amniotes finds it as an archosauriform archosauromorph, increasing known archosauriform diversity in the Early Triassic. The fauna of the lower Fremouw Formation traditionally has been considered to represent a subset of the Lystrosaurus Assemblage Zone of the Karoo Basin, with differences largely a result of pronounced differences in sampling intensity. However, a review of recent changes to the fauna, as well as a reassessment of occurrences based on older literature, indicates that significant discrepancies, including the co-occurrences of taxa known from both earlier and later in time and the presence of endemic forms in Antarctica, exist between the faunas of the Lystrosaurus Assemblage Zone and lower Fremouw Formation.
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Citation for this article: Peecook, B. R., R. M. H. Smith, and Christian A. Sidor. 2019. A novel archosauromorph from Antarctica and an updated review of a high-latitude vertebrate assemblage in the wake of the end-Permian mass extinction. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1536664.
The study reported on here was conducted to assess the impacts of historic coal mining activities at Elitheni Colliery in South Africa. Five boreholes and five water ponds were sampled during the summer of 2010 and winter of 2011. Physical characteristics (pH, EC, TDS) and hydrochemical characteristics (Na + , K + , Ca 2+ , Mg 2+ , HCO3-, Cl-, SO4 2-, F-, Pb and Fe) of the water were determined. To assess the suitability of the water for irrigation purposes, parameters such as total hardness, sodium absorption ratio (SAR), percentage sodium (% Na), residual sodium carbonate (RSC), permeability index (PI) and Mg ratio were calculated. The pH of the water ranged from 6.87 to 8.91, and electrical conductivity (EC) was between 4.5 and 94 mS/m. Total dissolved solids (TDS) ranged from 178 to 470 mg/L; spatial variations in TDS attest to variations in lithological composition, activities and prevailing hydrological regimes. HCO3-and SO4 2-were the dominant anions, while Na + was the dominant cation. Na-K-SO4 and Na-HCO3 were the dominant hydrochemical facies. Fe content was high in borehole water due to the oxidation of pyrite. On the basis of the calculated SAR, % Na, RSC, Mg ratio and salt content, it was concluded that the water can be used for irrigation purposes. The water quality analysis provided no conclusive evidence that historical mining activities have had any significant impact on the acidification of water resources in Elitheni Colliery. However, further studies are required to ascertain the ability of the aquatic environment and surrounding rocks to buffer any acid generated.
We investigate the bone histology of multiple skeletal elements of dinocephalian taxa from the middle Permian Tapinocephalus Assemblage Zone of the Karoo Basin of South Africa. The results show that the cortex is predominantly composed of fibrolamellar bone, suggesting rapid osteogenesis for these basal non-mammalian therapsids. However, in a few skeletal elements, growth marks interrupt the deposition of the fibrolamellar bone tissue, indicating periodic arrests in growth. Ontogenetic differences are observed among the specimens studied: the majority have fibrolamellar bone deposited up to the peripheral margin of the bone wall, indicating continuous fast growth right up to the time of death, while a few specimens have avascular lamellar bone tissue with multiple, closely spaced rest lines, indicating maturity and a slowing down of growth prior to death. Several taxon-specific histological variations in terms of orientation of vascular canals and primary osteons, incidence of growth marks, and extent of secondary medullary reconstruction suggest slight differences in growth trajectories between the different taxa. The skeletal elements of the herbivorous taxa (Keratocephalus, Moschops and Struthiocephalus) and the omnivorous Jonkeria, previously studied, are characterized by a thick cortex, and extensively developed medullary spongiosa, suggestive of semi-aquatic habits. In contrast, the femoral histology of the carnivorous Anteosaurus suggests that it was more terrestrial.
We present results of rock and paleomagnetic magnetic analyses of a ~671 m-thick continuous vertical drill core(KZF-1) that intersect the lower Ecca Group (early-mid Permian) of the southwestern Karoo Basin, South Africa. Rock magnetic and optic microscopy experiments indicate monoclinic pyrrhotite and single-domain magnetite in the mudstones, shales, and siltstones as carriers of characteristic remanent magnetization (ChRM), which is likely a post-detrital remanent magnetization. Stepwise demagnetization and removal of low-coercivity and thermally less stable magnetizations reveal the preservation of a dual polarity ChRM in 90 samples. These are used to construct a magnetostratigraphic profile for the core that is dominantly reversed polarity with four short normal polarity subchrons. Correlation with published U-Pb SHRIMP and CA TIMS ages and the proposed composite reference section for the Early Permian allows us to propose an Artinskian (281 Ma) to Kungurian (276 Ma) age for the lower Ecca Group rocks. Our magnetostratigraphic profile can be tied in with published profiles from the mid to Upper Ecca Group to produce the first composite profile that spans all of the Ecca Group in the southwestern region of the Karoo Basin.
The astounding diversity of life that we see today is the product of species multiplication and morphological divergence through geological time. Evidence from the fossil record shows that this evolutionary radiation has not occurred at an even rate. Instead, relatively short-lasting phases of evolution have produced the major radiations that are seen in many taxonomic groups, such as flowering plants during the late Cretaceous. This volume surveys patterns of major evolutionary radiation and their possible causes.
Book synopsis:"In the last twenty years or so there has been an upsurge in the study of Palaeozoic fishes for solving geological problems, both in areas of biostratigraphy and biogeography. This has resulted in an explosion of data, much of it so new that it will take years for all the recent discoveries to be published. This book has resulted to fill the need to provide up-to-date summaries of global work in progress showing the application of both macroscopic and microscopic remains of Palaeozoic vertebrates to geological correlations, and to refinement of global palaeogeographic reconstructions."--from the Preface. This book offers the first detailed treatment of palaeozoic vertebrates for use in correlations and in biogeographic studies. With thirteen chapters of systematic analysis of biostratigraphic and biogeographic data, it includes invaluable summaries of current research as well as new and significant contributions to the fields of geology and evolutionary biology. With charts and figures that show many of the important fossils discussed in the text, as well as stratigraphic, location, and taxonomic indexes, the book will interest palaeontologists, stratigraphers, and other earth scientists concerned with the early history of life on earth.
The possible origin of birds from either theropod dinosaurs, primitive archosauromorphs or crocodilomorphs has previously been postulated. In this paper, aspects of the morphology of the braincases of a relevant example of each of these possible ancestors, Syntarsus, Euparkeria and Sphenosuchus, were compared with those of birds. As a result, an alternative hypothesis to the theropod and crocodilomorph origin of birds is proposed, supported by a number of synapomorphies shared by birds, Euparkeria and Archaeopteryx. -Author
Fragmentary remains of a new heterodontosaurid species, comparable to Heterodontosaurus Crompton and Charig, were discovered in concretions in the Laguna Colorada Formation, a Late Triassic continental sequence in Santa Cruz Province, Argentina. The material consists of a weathered, left posterior maxillary fragment with dentition, and, tentatively, an isolated caniniform with anterior and posterior serrations. The preserved three maxillary teeth bear flat wear facets, and are columnar and closely packed. The anterior and posterior surfaces of the crowns are in contact, a feature considered a synapomorphy of Heterodontosaurus and Lycorhinus from the Early Jurassic upper Stormberg Group of southern Africa. As in Heterodontosaurus tucki Crompton and Charig, the maxillary teeth lack a cingulum or a constriction separating crown and root, and the wear facets of adjoining teeth form a single, continuous surface. However, the posterior maxillary teeth bear more. numerous and narrower ridges on their labial surfaces than those of H. tucki. This new record of a heterodontosaurid extends the temporal range of this group of small ornithischians and, considering the phylogeny of ornithischians as now understood, indicates an extensive phyletic diversification of these dinosaurs in the Late Triassic.
The Triassic reptile Euparkeria has been frequently given a pivotal position in interpretations of the evolution of archosaurs. Most recently, Welman (1995) has argued from braincase data that Euparkeria is more closely related to birds than are either theropod dinosaurs or crocodilians - a conclusion clearly at odds with the current orthodoxy. The braincase of a single specimen of Euparkeria is described in detail and compared with previous descriptions and with the braincases of other diapsids. Variations among the known specimens are documented. The homology of various braincase structures are reassessed in light of the study by Welman (1995). We argue that the braincase of Euparkeria has an undivided metotic fissure, an incompletely ossified medial wall of the otic capsule, a well-defined ‘semilunar depression’, and posteroventrally positioned foramina in the parabasisphenoid for the entrance of the cerebral branches of the internal carotid arteries. It lacks enclosure of the Eustachian system in bone, well-developed tympanic sinuses, or a well-defined recess for the lagena. A review of braincase morphology in extinct and extant diapsids suggests that braincase features of Euparkeria are largely plesiomorphic for Archosauria. The evolutionary relationships between Euparkeria and extant archosaurs (birds and crocodilians) are considered by reviewing braincase morphology in extant and extinct diapsids. No shared derived characters could be found that support the resolutions (crocodilians (Euparkeria+ birds)) or (birds (Euparkeria+ crocodilians)). Three derived characters shared by extant archosaurs support the resolution (Euparkeria (crocodilians + birds)), but only the presence of laterally positioned foramina in the parabasisphenoid for the entrance of the cerebral branches of the internal carotid arteries appears to represent strong evidence. The other two features are a degree of ossification (of the medial wall of the otic capsule) that exhibits some homoplasy among archosaurs, and an absence (of the ‘semilunar depression’), and therefore do not represent particularly robust hypotheses of homology. Our interpretation of the braincase of Euparkeria is fully congruent with the consensus among recent explicit phylogenetic analyses that this taxon is close to, but not a member of, the archosaur crown group. Birds and crocodilians share a number of other derived similarities (subdivided metotic fissure, elongated and tubular cochlear recess, enclosed Eustachian system, extensive tympanic sinuses, quadrate-prootic articulation) that are probably not homologous because of their absence in a number of non-avian dinosaurs and crocodilian-line crown-group archosaurs.
Two new mastodonsaurid temnospondyls are described from the Early to Middle Triassic Cynognathus Assemblage Zone of the Upper Beaufort Group (Karoo Basin) of South Africa. Paracyclotosaurus morganorum, sp. nov. is based on a partial skull from the uppermost part of the Cynognathus Assemblage Zone (Subzone C; late Anisian) in the southern Karoo Basin, and is the first occurrence of the genus Paracyclotosaurus outside of India and Australia. Jammerbergia formops, gen. et sp. nov. is based on a partial skull, presumably from Subzone B (early Anisian) of the Cynognathus Assemblage Zone, and is distinctive in its unique suite of primitive and derived characters. Although the intrarelationships of mastodonsaurids remain largely unresolved, the two most recent analyses are similar in the identification of an ‘advanced’ mastodonsaurid clade whose members are characterized by laterally directed tabular horns. Jammerbergia probably belongs within this clade, albeit within a basal position. Jammerbergia and Paracyclotosaurus share the synapomorphy of large, antero-posteriorly expanded tabulare, and may represent sister taxa. The Cynognathus Assemblage Zone is characterized by three subzones of differing ages and faunas, with no overlap in the temnospondyls between the subzones.
An assemblage of five fully-articulated juvenile skeletons of Youngina has been recovered from the Late Permian strata of the south-western Karoo Basin. They are preserved in overbank mudrocks of the Hoedemaker Member 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. -from Authors
The smaller Endothiodontidae were taxonomically revised in order to achieve a finer biostratigraphic tool for the subdivision of the Adelaide Subgroup of the Beaufort Group. The cranial morphology of Pristerodon mackayi Huxley is described and the variability of the various features used in the taxonomic subdivision of the smaller endothiodonts are discussed in some detail. Particular attention was given to variability of the dentition. The taxonomy of the group was approached from the point of view that a number of fossils from a limited area and stratigraphic range constitute a sample of a once living population of animals and that the variation encountered in such a sample reflects the variability of a once living biospecies. A series of 20 skulls were selected to compare the holotypes of the 49 described species of small endothiodonts. It was concluded that the vast majority of the described species are junior synonyms of Pristerodon mackayi Huxley. Many taxa were considered to be nomina dubia because of inadequate type specimens. -from Author
The structure and functioning of the dicynodont jaw system are described. A pivoting action of the lower jaw around the palate posteromedian to the caniniform processes is as basic to the jaw movement as is the well-known double-convex jaw articulation. The sequence of origin of the characteristic features of the dicynodonts is analysed cladistically; this demonstrates the patterns of association of these characters into functional character-complexes. The structures of the palate and lower jaw, and their functional integration in feeding, are described and illustrated in standard format. Five different lineages of dicynodont can be identified: Eodicynodon: the robertoids (including Diictodon); the dicynodontoids (including Dicynodon and the majority of the large dicynodont genera of the Permian and Triassic) the endothiodontoids (including Prodicynodon [= 'Chelydontops'] and Pristerodon), and the emydopoids (including Cistecephalus, Myosaurus and Kingoria). Eodicynodon or a similar form could have been ancestral to the other four lineages. The robertoids probably fed upon the stems and rkizomes of equisetaleans, while the varied dicynodontoids probably fed upon the varied glossopterid seed-ferns. The endothiodontoids, too, were probably herbivorous, but many, perhaps all, of the small emydopoids were burrowing and may have been omnivorous. The dicynodonts were probably ectothermal, and the dicynodontoids may have migrated to warmer latitudes in the winter. Only c. 20 genera of Karoo dicynodont are now recognized as valid, and it is suggested that this fauna is now almost completely known. Their distribution in the Karoo biozones is reviewed and correlated with environmental changes. The Permian ancestors of the Triassic dicynodonts, including Lystrosaurus, probably lived on higher, drier ground, and were therefore already adapted to the more fibrous food that spread into the basins as the climate became drier in the Triassic. (C) 1997 The Linnean Society of London.
A new capitosaurid temnospondyl from the upper part of the Cynognathus Assemblage Zone of the Permo-Triassic Beaufort Group represents the first occurrence of the genus Paracyclotosaurus in South Africa. The discovery, in the southern part of the Karoo Basin, represents part of a new fauna considered to be of Anisian (early Middle Triassic) age. Paracyclotosaurus is also known from the Middle Triassic of Australia and India, and its discovery in the Cynognathus Assemblage Zone suggests a late Anisian age for the upper part of this biozone.
The Gondwana Sequence in the northern part of the Pranhita-Godavari Valley consists of four formations of the Lower Gondwana and seven formations of the Upper Gondwana. The gross lithological characters and mappability are considered as the major criteria for delineating the formations. The name Kamthi Formation which has been used by different authors in different senses, is here used in the sense of Sengupta (1970). The rocks between the Barakar and this Kamthi are divided into four lithozones for limitations of mappability. Although some of these lithozones have earlier been designated as formations, at present not sufficient information is available to justify this. Only two breaks, both within the Upper Gondwana, are found to be present: there is no recognisable break between the Lower and the Upper Gondwana. A summary of this succession is presented in tabular form taking into account the words of earlier authors. The alternative views that are radically different from the one presented here are also discussed briefly. The usefulness of plant megafossils and fossil vertebrates in understanding the stratigraphy is discussed briefly and their role in determining the possible geological ages of some of the formations is mentioned. The vertebrate fauna from a number of formations is listed. At least seven formations are fossiliferous as far as vertebrates are concerned. Of these, two belonging to the Triassic and one belonging to the Jurassic are quite well-documented. The other four are less well known, but serve as very useful time markers. All these vertebrate-bearing formations can be correlated with co-eval rocks elsewhere in the world. The difficulty of correlating continental deposits is realized and keeping this in view a tentative correlation is presented.
We have now positively identified a number of specimens of the formerly exclusively South American Stereosternum tumidum in the Great Karoo Basin of South Africa, and an osteological study has shown Mesosaurus tenuidens and M. braziliensis to be conspecific. The occurrence of the same mesosaurid species in the Southern African and South American Gondwana is of importance for 2 reasons: it constitutes the earliest record of a shared reptile species on different Gondwana continents, and it is the first record of a reptile species shared by Southern Africa and South America. Even the widespread genus Lystrosaurus, known from South Africa, Antarctica, India and China, has not yet been discovered in South America in spite of the recent discovery of other, only slightly older African genera such as Pareiasaurus and Procolophon in Brazil.-from Authors
Size-related differences have previously been considered to be important in distinguishing the four proterosuchian archosauromorph species described from South Africa. Previous authors hypothesized that these differences were due to allometric growth. In this study, a statistical analysis of 85 parameters measured in 12 skulls, including all the type specimens, has been carried out. The results show that all the specimens can be fitted into a growth series. Variation in the the growth rate of parts of the proterosuchid skull and the possible function significance of such allometric growth patterns are investigated. -from Authors
Palacrodon browni Broom 1906 (=Fremouwsaurus geludens Gow 1992) is a small enigmatic diapsid reptile from the Cynognathus Assemblage Zone of South Africa and Antarctica whose dentition is very similar to that of coeval procolophonids.
Until now, no therapsid was known with any certainty from Malagasy. The present specimen discovered in 1948, but never described, is the first record of a complete dicynodont skull from this country. A description of the skull is given and it is referred to a new species of the genus Oudenodon. The rarity of dicynodonts in Malagasy may be because of environmental differences from the adjoining landmass of Africa. -Authors
Predatory therapsids from the Ezhovo locality (Otcher Faunal Assemblage, Late Permian; Fore-Urals) are revised. Eotitanosuchus olsoni, Biarmosuchus tener, and Ivantosaurus ensifer are shown to be synonyms. B. tener is considered to be the senior synonym. A new species Biarmosuchus tchudinovi (Sokol locality, Udmurtia) is described. The family Eotitanosuchidae is considered to be a member of the order Titanosuchia, superorder Dinocephalia.