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Vertebrate biozonation of the Beaufort Group with special reference to the western Karoo Basin
... In particular, the Abrahamskraal Formation can be distinguished from the underlying arenaceous deltaic sediments of the Waterford Formation (top of the Ecca Group) by the first appearance of red/purple mudstones considered to represent the first subaerial fluvial deposition and from the overlying Teekloof Formation based on the sandstone percentage, the presence of chert beds, and the abundance of purple mudstone [32]. The Abrahamskraal Formation is well developed in the southern and southwestern parts of the main Karoo Basin and consists of predominantly grey, bluish to greenish-grey, and olive-green mud-stone and siltstone with subordinate mottled, light grey, yellow-brown, greyish orange to greenish grey sandstone. ...
... The Abrahamskraal Formation has yielded diverse tetrapod fossils which belong to the Tapinocephalus Assemblage Zone [22,39]. The fauna comprises mostly therapsids (Dinocephalia, Dicynodontia, Therocephalia, Gorgonopsia, Biarmosuchia, basal Anomodontia) with less common reptiles (pareiasaurs and Eunotosaurus), rhinesuchid temnospondyls, and rare fish [32,37,38,[40][41][42][43]. Fossil plants are also present in silicified wood fragments, stems, and leaves, some of which are preserved in a growing position [34,44]. ...
... Different interpretations were carried out to explain the multiple fining-upwards cycles characterizing the mostly fine-grained Abrahamskraal Formation and the overlying Teekloof Formation, even ascribing them to astronomically forced cycles [49]. Most authors agree in considering this sedimentation to be typically fluvial [32,50]. These latter authors ascribed the Abrahamskraal Formation facies associations as related to dominantly highsinuosity channels and the Teekloof Formation facies as pertaining to floodplain deposits. ...
The Gansfontein palaeosurface (Fraserburg, Karoo, South Africa), which is correlated with the stratigraphic lowermost part of the continental Middle-Upper Permian Teekloof Formation, is revisited. This treasure trove of peculiar and exquisitely preserved sedimentary structures and invertebrate and vertebrate traces serves as a document of a set of fluvial paleoenvironments ranging from small ponds to marginal lacustrine and muddy riverine outer banks. It represents an isolated and relatively small "oasis" within the dominating sedimentary environments of the Teekloof Formation characterized by fine and medium-grained siliciclastics related to repeated higher-energy flooding events. The vertebrate traces include abundant therapsid trackways and, locally, tetrapod swimming traces. Tetrapod footprints show a very variable preservation in different areas of the palaeosurface, and it also changed based on the time of impression. Fish trails (Undichna) are relatively common. The invertebrate ichnofauna is comprised of abundant arthropod traces and horizontal burrows; however, the palaeosurface was not intersected by intense bioturbation. The occurrence of this scenario of abundant life reflects complex interaction among different tracemakers with the substrate and is evidence of a relatively quiet palaeoenvironment, which was suddenly submerged and sealed during a flooding event. Sedimentological and ichnological insights from such a palaeosurface, therefore, opens a rare window into Middle Permian ecosystems in southernmost Gondwana.
... Previous criteria for determining the contact range from the first appearance of reptilian fossil remains (Schwarz, 1896;Rogers et al., 1909), the first appearance of purplish shale or mudstone (e.g. Mountain, 1946;Keyser and Smith, 1979), the base of the first sandstone displaying an erosive contact (Loock and Grobler, 1988), and the base of the first prominent sandstone overlying the argillaceous Ecca Group (Rogers et al., 1909;Ryan, 1967;Zawada, 1988a;Zawada and Cadle, 1988;Groenewald, 1989;Muntingh, 1989Muntingh, , 1997. This has resulted in mismatch of the placement of the Table modified from Barbolini et al. (2016) with additional data from Viglietti (2016), Cole et al. (2016), and Smith et al. (2020). ...
... Because of this, current understanding of vertebrate distribution in the main Karoo Basin and mid-to late Permian Beaufort Group biostratigraphy is based mostly on results from the southern parts of the basin (e.g. Kitching, 1977;Keyser and Smith, 1979;Rubidge, 1995Rubidge, , 2005Mason, 2007;Rubidge et al., 2013;Mason et al., 2015;Smith et al., 2020). ...
... This study focuses on rocks of the Adelaide Subgroup, which comprises a succession of mudstones and sandstones generally interpreted as having been deposited in various terrestrial fluvial to lacustrine environments Johnson et al., 2006;Paiva, 2015). In the south-western part of the basin, the Adelaide Subgroup comprises sandstones and mudrocks of the Abrahamskraal and Teekloof formations ( Fig. 1), with the former characterised by the presence of a number of cherty beds and less red mudstone relative to the overlying Teekloof Formation (Keyser and Smith, 1979;SACS, 1980). In the south-eastern areas, it comprises the Abrahamskraal, Middleton and Balfour formations (Johnson, 1976;Day and Rubidge, 2014;Cole et al., 2016;Viglietti et al., 2017aViglietti et al., , 2017b. ...
The Karoo Supergroup of South Africa, internationally renowned for its almost continuous Carboniferous to Jurassic record of deposition in a foreland basin setting, hosts an unparalleled record of fossil tetrapods that provides unique insight into terrestrial biodiversity change over this extended period. Understanding of the litho-, bio- and chronostratigraphy of the Karoo Basin has greatly improved in recent years but most work has focused on the thicker and better-exposed rocks in the basinal foredeep. A core issue that has remained ambiguous is the stratigraphic placement of the diachronous Ecca-Beaufort contact, for which different criteria have been used during mapping in different parts of the main Karoo Basin. Comparison of biostratigraphy and contrasting lithological facies changes with those in the better-studied foredeep enabled us to revise the lithostratigraphy of the Ecca and Beaufort groups in the distal part of the main Karoo Basin. The presence of proximal marine facies associations in the distal sector conform with the definition of the Waterford Formation of the Ecca Group, so far recognised only in the southern foredeep. The upper contact of the Waterford Formation represents a change from a subaqueous to a subaerial delta plain depositional environment and marks the boundary between the Ecca and Beaufort groups, as in the south. This has consequences for Beaufort Group stratigraphic subdivision in the distal sector of the Karoo foreland basin.
... Tectonics and climate, the two main allogenic forcing mechanisms of continental deposition (Shanley and McCabe, 1994;Allen et al., 2002;Catuneanu, 2006), are fundamentally associated with the history and evolution of the Lower Beaufort Group in the main Karoo Basin (MKB) of South Africa (Figure 1). The overall tectonic and climatic settings of the basin in the Permian are thought to be fairly well understood (Keyser and Smith, 1978;Smith, 1979, Smith 1987Catuneanu et al., 1998, Catuneanu andBowker, 2001;Cole and Wipplinger, 2001;Catuneanu et al. 2005;Bordy et al., 2011). However, the intertwined impact of the two mechanisms on the Karoo sedimentation patterns is often difficult to determine at time scales < 10 6 years. ...
... 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 stratigraphic interval studied here ( Figure 1C) is from the Lower Beaufort Group and straddles the uppermost part of the Abrahamskraal and the lowermost Teekloof Formations in two regions of the southwestern and southern MKB (abbreviated here as SW-MKB and S-MKB, respectively, and further subdivided into W1, W2, and E study sectors- Figure 1). The studied succession ( Figure 1C) was described from the SW-MKB in sedimentological (Stear, 1978, Stear, 1980, Stear, 1983, Stear, 1985Smith, 1987, Smith, 1990Gulliford et al., 2014;Wilson et al., 2014), biostratigraphic, and taphonomic studies (Keyser and Smith, 1978;Loock et al., 1994;Smith, 1979, Smith, 1993. These studies have established that the deposition of this Permian succession occurred in a fluviolacustrine setting under a semi-arid climate. ...
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.
... Kitching nevertheless maintained his opinion, similar to Watson's, that the 'Old Endothiodon Zone' represented a local anomaly in Endothiodon abundance (Kitching, 1977). Keyser and Smith (1978) recognised two new biozones between the Tapinocephalus Zone and Cistecephalus Zone, which together covered much of the same stratigraphic interval as Broom's Endothiodon Zone: these were the older Pristerognathus/Diictodon Assemblage Zone and the younger Tropidostoma microtrema Assemblage Zone. These were later renamed the Pristerognathus and Tropidostoma Assemblage zones Keyser, 1995a, 1995b). ...
... The first occurrence of Endothiodon was considered by Keyser and Smith (1978) to occur around the same time as the first occurrence of Tropidostoma, which may have led them to draw the boundary of the Tropidostoma microtrema Assemblage Zone as far south as Beaufort West town; however, these authors later recognised that Endothiodon appeared lower in the section (Smith and Keyser, 1995a) and so depicted the strata surrounding Beaufort West as part of the underlying Pristerognathus Assemblage Zone. The Pristerognathus Assemblage Zone thus incorporated both the stratigraphic-range overlap of Endothiodon and scylacosaurid (viz. ...
... The upper subdivision of the Endothiodon Assemblage Zone proposed by Watson (1942), in which tusked dicynodonts of medium size occur, described a roughly similar assemblage to that which was later designated the Tropidostoma microtrema Assemblage Zone (Keyser and Smith, 1978). This assemblage zone has remained in use since. ...
The Endothiodon Assemblage Zone is the third oldest tetrapod biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup). It is situated between the underlying Tapinocephalus and overlying Cistecephalus assemblage zones and in the southwestern part of the basin corresponds to the majority of the Poortjie and Hoedemaker members of the Teekloof Formation. It is characterised by the dicynodont genus Endothiodon, especially in the lower part of assemblage zone, and records early ecosystem recovery from the Capitanian mass extinction. It also contains the lowest occurrence in the Karoo Basin of cynodont therapsids, eutherocephalians, bidentalian dicynodonts, and diapsids. The biozone reaches a maximum thickness of around 250 m in the southwestern part of the basin. We propose a two-fold subdivision into a lower Lycosuchus - Eunotosaurus Subzone (equivalent to the upper two-thirds of the former Pristerognathus Assemblage Zone) and an upper Tropidostoma - Gorgonops Subzone (equivalent to the former Tropidostoma Assemblage Zone), with the contact defined by the first appearance of Tropidostoma dubium. The Endothiodon Assemblage Zone is terminated by the first appearance of Aulacephalodon bainii.
... Broom (1906aBroom ( , 1907Broom ( , 1909a formulated a more precise biostratigraphic division of the fossiliferous horizons of the Beaufort Group and in his scheme Seeley's Zone of specialised theriodonts was renamed the Cynognathus Zone, and this was accepted by Kitching (1970Kitching ( , 1972Kitching ( , 1977. Keyser and Smith (1978) introduced the terminology Kannemeyeria Assemblage Zone to replace the Cynognathus Zone. The dicynodont Kannemeyeria was preferred over Cynognathus as the zone's index fossil as the authors believed that Cynognathus was rare, and that it was impossible to accurately establish its biostratigraphic range. ...
... He subdivided the zone into a lower zone (A), in which Kannemeyeria and Erythrosuchus occurred together, and an upper zone (B), in which Kannemeyeria was absent and Erythrosuchus was extremely rare. This biostratigraphic range for Kannemeyeria was corroborated by Kitching (1977) and Cooper (1982), but refuted by Keyser and Smith (1978) who believed that Kannemeyeria occurred throughout the biozone. Cooper (1982) felt that Kannemeyeria was restricted to the lower half of the Burgersdorp Formation, and further suggested that the upper part of the Cynognathus Assemblage Zone, above the biostratigraphic range of Kannemeyeria, would eventually yield an advanced fauna, equivalent to his Tetragonias Zone fauna. ...
... He also considered the cynodont genera Cynognathus and Diademodon to occur throughout the range of the Cynognathus Assemblage Zone. It should be noted that these trends were for the Cynognathus Assemblage Zone as known at the time, and before the recognition of the lowermost and uppermost subzone faunas (Kitching, 1977;Keyser and Smith, 1978;Cooper, 1982). ...
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.
... As a result, Kitching's 'Daptocephalus Range Zone' was renamed the Dicynodon Assemblage Zone (DiAZ) by Keyser and Smith (1979) who introduced the assemblage zone concept to the Beaufort Group. Additionally, Keyser (1979) later adopted a scheme whereby two genera were used to define each assemblage which was ratified by SACS (1980) to conform to the International Sub-Comission on Stratigraphic Classification (Hedberg, 1976) regulations on stratigraphic nomenclature. ...
... As a result, Kitching's 'Daptocephalus Range Zone' was renamed the Dicynodon Assemblage Zone (DiAZ) by Keyser and Smith (1979) who introduced the assemblage zone concept to the Beaufort Group. Additionally, Keyser (1979) later adopted a scheme whereby two genera were used to define each assemblage which was ratified by SACS (1980) to conform to the International Sub-Comission on Stratigraphic Classification (Hedberg, 1976) regulations on stratigraphic nomenclature. Thus, the DiAZ became the Dicynodon lacerticeps-Whaitsia Assemblage Zone for a brief period, but updated recommendations by the ISSC (Salvador, 1994) meant Beaufort Group assemblage zones should revert to the use of a single genus in the name for the zone. ...
... In his full description of the new biozone Kitching (1977) used the range of Daptocephalus as the index fossil for his original 'Daptocephalus Range Zone'. This biozone was subsequently redefined as the Dicynodon Assemblage Zone by Keyser and Smith (1979) because of the then accepted, and later published synonymy of Daptocephalus leoniceps with Dicynodon lacerticeps (Cluver and Hotton, 1981). This was formally accepted by SACS as the Dicynodon-Theriognathus Assemblage Zone (Keyser 1979) to be later shortened to Dicynodon Assemblage Zone (Kitching, 1995). ...
The name Daptocephalus Assemblage Zone (DaAZ) is re-instated for vertebrate assemblages of the uppermost Permian strata (Balfour, upper Teekloof, and Normandien formations) of South Africa’s main Karoo Basin (MKB). This involved taxonomic revision of the dicynodontoid “Dicynodon” sensu lato, reviving Daptocephalus leoniceps, and revising the stratigraphic ranges of co-occurring index taxa (Theriognathus microps, Procynosuchus delaharpeae) of the Dicynodon Assemblage Zone (DiAZ) as it was known. This work has demonstrated the appearance of index taxa below the stratigraphically defined DiAZ. Moreover, the first appearance of Lystrosaurus maccaigi and Moschorhinus kitchingi in the upper reaches of the biozone calls for the establishment of a two-fold subdivision of the current DaAZ into lower (Dicynodon-Theriognathus) and upper (Lystrosaurus maccaigi-Moschorhinus) subzones. The biostratigraphic utility of Daptocephalus and other South African dicynodontoids outside of the MKB is limited due to basinal endemism at the species level and varying temporal ranges of dicynodontoids globally. Accordingly, their use is recommended only for correlation within the Karoo Basin at this stage.
... It was the first recognition of the impoverished fauna that would later be identified as the result of the Capitanian extinction event Day et al., 2018). Keyser and Smith (1978) noted that Boonstra's divisions were not workable biostratigraphic units and that the upper and lower divisions of the Tapinocephalus Assemblage Zone were indistinguishable without extensive collecting. Therefore, they did not formalise them and considered both together to constitute their 'Dinocephalian Assemblage Zone'. ...
... This was a reasonable solution, as Tapinocephalus itself is represented by only a few specimens, but it did not conform to the regulations of the International Commission on Stratigraphy and so the name Tapinocephalus-Bradysaurus Assemblage Zone was chosen instead (Keyser, 1979). The uppermost part of the original Tapinocephalus Zone, corresponding to the same stratigraphic interval identified by Rossouw and de Villiers (1953), was, conversely, detached from the Dinocephalian Assemblage Zone and placed into a new biozone: the Pristerognathus-Diictodon Assemblage Zone (Keyser and Smith, 1978). Shortly thereafter, collecting efforts in the lowest Beaufort strata revealed that the Dinocephalian Assemblage Zone did not extend down to the base of the Beaufort Group, and was in fact preceded by an older assemblage designated the Eodicynodon-Tapinocaninus Assemblage Zone (Rubidge, 1990). ...
... The Dinocephalian Assemblage Zone as described by Keyser and Smith (1978) was practically unchanged by Smith and Keyser (1995), although the name was formally reverted to the Tapinocephalus Assemblage Zone. These authors attempted to plot the ranges of individual taxa within the biozone but most suffered from considerable uncertainty. ...
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.
... Finer lithostratigraphic subdivisions of the lower Beau- fort into formations and members were developed in the latter half of the 20th century (Johnson 1976;Keyser & Smith 1979;Stear 1980;Turner 1981;Le Roux 1985;Jordaan 1990), during which time the biostratigraphy was further revised and formally linked to lithostratigraphic units (Kitching 1977;Keyser & Smith 1979;Rubidge 1995). In the southwestern part of the basin, these relationships are based mostly on collections along the Nuweveld Mountains extending west from Beaufort West and south towards the Swartberg Mountains; this was a result of the extensive vertical exposures along the escarpment and the relative ease of correlating horizons, and was also driven by desire for biostratigraphic constraints on the uranium- bearing sandstones of Poortjie Member, which crops out along much of the escarpment. ...
... Finer lithostratigraphic subdivisions of the lower Beau- fort into formations and members were developed in the latter half of the 20th century (Johnson 1976;Keyser & Smith 1979;Stear 1980;Turner 1981;Le Roux 1985;Jordaan 1990), during which time the biostratigraphy was further revised and formally linked to lithostratigraphic units (Kitching 1977;Keyser & Smith 1979;Rubidge 1995). In the southwestern part of the basin, these relationships are based mostly on collections along the Nuweveld Mountains extending west from Beaufort West and south towards the Swartberg Mountains; this was a result of the extensive vertical exposures along the escarpment and the relative ease of correlating horizons, and was also driven by desire for biostratigraphic constraints on the uranium- bearing sandstones of Poortjie Member, which crops out along much of the escarpment. ...
... Day et al. 2018), and because fossils from the Victoria West district, collected mostly by the Geological Survey, represent a considerable proportion of late Permian fossil occurrence data from the western Karoo. Because the biostratigraphic succession of the Karoo provides the most complete record for terrestrial vertebrates between the late Guadalupian and the Middle Triassic (Broom 1906;Watson 1914;Kitching 1970;Keyser & Smith 1979;Rubidge 1995;Lucas 1998Lucas , 2006Lucas , 2017, any confusion over the age (and/or host assemblage zone) of fossils in the Victoria West area has the potential to bias analyses of tetrapod diversity in the mid-late Permian, if these data are included. In order to clarify the situation from a biostratigraphic perspective, we conducted fieldwork in the vicinity of Biesiespoort railway siding and reviewed the published literature to determine the assemblage zones present, as well as their local stratigraphic extent. ...
The relationship between the tetrapod assemblage zones of the South African Karoo Basin and the lithostratigraphic divisions of the
Beaufort Group is well-established, and provides an independent means of dating fossil occurrences. However, this relationship may
not be consistent across the basin; a discrepancy exists between the historical tetrapod assemblages in the vicinity of Victoria West,
Northern Cape Province, and the expected tetrapod assemblage zones based on mapped geology. In order to examine this disconnect,
we collected fossils at two localities close to Biesiespoort railway station, a locality that was visited on a number of occasions by Robert
Broom. Our fossil samples support the biostratigraphic determinations of Broom and thus confirmthat the stratigraphic extent of the
biozones at these localities differs from their type areas further south. The reasons for this are unclear but could be related to the northward
younging of the lithological units, implying complex depositional processes, or result from difficulties in mapping. Nevertheless,
caution should be exercised when using mapped geology near Victoria West as a guide to the age of fossils found there.
... Soon after Kitching's (1977) publication, Keyser & Smith (1977) published another biostratigraphic subdivision of the Beaufort Group, which for the first time was closely integrated with their proposed lithostratigraphic units. This was primarily aimed at the southwest of the Karoo basin but earlier mapping in the east by Keyser (1973) had already revealed a link between the lowest appearance of Cistecephalus and a unit called the Oudeberg sandstone in the region of Graaff-Reinet. ...
... The 'Daptocephalus Zone', while maintaining its integrity, was renamed the Dicynodon Assemblage Zone (AZ) because the former genus was in the process of being synonymized with the latter (Cluver & Hotton 1981). The name 'Cistecephalus Zone' was discarded due to its confusing history of use, as well as its uneven occurrence; instead, Keyser & Smith (1977) considered Aulacephalodon baini to be a far superior index fossil and so adopted the name without much change in the stratigraphic extent of the biozone. ...
... They also supported this designation with lithological characteristics. Keyser & Smith (1977) also formally subdivided the Tapinocephalus AZ for the first time, based partly on the work of Rossouw & de Villiers (1953) and of Boonstra (1969). The upper division of Boonstra (1969) was now considered separate and renamed the Pristerognathus/ Diictodon Assemblage Zone, defined by the abundance of these genera there in the absence of dinocephalians. ...
The interest in the fossil remains of the Beaufort Group and their stratigraphic significance goes back as far as the earliest geological studies in South Africa in the early 19th century. By the 1890s, the understanding of fossil distributions in the sedimentary rocks of the Karoo allowed the formulation of the first tetrapod biostratigraphic subdivisions. Since the beginning of the 20th century, the highest resolution subdivisions of the mostly undifferentiated fluvial sediments of the Beaufort Group have been biostratigraphic. More recent biostratigraphic studies in the Lower Beaufort Group have been crucial in understanding terrestrial ecological change in the Middle and Late Permian, and continue to be a leading area of research in South Africa palaeontology.
... Middle Permian (Wordian to Capitanian) age indicated by vertebrate (therapsid) fossils (Rubidge, 1995(Rubidge, , 2005Smith and Keyser, 1995a) and published U-Pb dates of ~268 to 264 Ma for juvenile magmatic zircons from tuff beds located in the lower Abrahamskraal Formation at Ouberg Pass, west of Sutherland (Lanci et al., 2013), and a date of 261.24 from a tuff bed in the upper part of the Abrahamskraal Formation (formerly Koonap Formation) on the farm Uintjies Vlakte 118 some 20 km west-northwest of Jansenville ( Figure 1; Geological Survey, 1993; Rubidge et al., 2013). The lower boundary of the formation becomes younger towards the east (Mason et al., 2015;Modesto et al., 2001) and northeast (Keyser and Smith, 1979;Rubidge, 2005) and is overlapped by the Middleton Formation in the vicinity of Petrusville (Figure 1). ...
... Vertebrate fossils are reasonably common in the mudstones. The fauna comprises diverse tetrapods (mostly therapsids [Dinocephalia, Dicynodontia, Therocephalia, Gorgonopsia, Biarmosuchia, basal Anomodontia] with minor Parareptilia [pareiasaurs and Eunotosaurus], rhinesuchid temnospondyls and rare basal synapsids) and occasional fish (Keyser and Smith, 1979;Rubidge, 1995;Keyser, 1995a, 1995b;Jirah and Rubidge, 2014). Two faunal assemblage zones are present: (1) Eodicynodon characterised by the presence of Eodicynodon and Tapinocaninus, which occur within the lowermost part of the formation in the extreme south (Rubidge, 1995) and cover a maximum stratigraphic thickness of 1104 m (Jirah and Rubidge, 2014); (2) Tapinocephalus characterised by the presence of Tapinocephalus and Bradysaurus and the absence of Eodicynodon and Tapinocaninus, occurring throughout the formation over a maximum thickness of 1441 m (Jirah and Rubidge, 2014) with the exception of the lower part of the formation in the extreme south. ...
... Glossopteris leaf impressions are abundant in the formation east of longitude 24°E (Mason, 2007). Lamellibranchs have been found in the basal part of the formation south of Beaufort West (Palaeanodonta; Rossouw, 1970) and higher in the succession elsewhere (Palaeomutela; Keyser and Smith, 1979;Smith and Keyser, 1995a). Bioturbation is common in mudrock and trace fossils include Planolites and Undichnus (fish trails). ...
The Middle Permian Abrahamskraal Formation is the lowermost formation of the lower Beaufort Group (Adelaide Subgroup, Karoo Supergroup) in the main Karoo Basin. It has been amalgamated with the lithologically similar and age-equivalent Koonap Formation and now occupies the entire southern part of the main Karoo Basin. It consists of greenish-grey and less common reddish-brown mudrock and subordinate light grey fine-grained sandstone, arranged in fining-upward, 1st to 3rd order cycles that range in thickness from a few metres to a few tens of metres. It reaches a maximum thickness in the southwest part of the basin (2200 to 2565 m) and thins northeastward with younging of the lower contact with the underlying Ecca Group and overlap of the overlying Middleton Formation onto the Ecca Group in the vicinity of Petrusville. The Abrahamskraal Formation contains several arenaceous zones in the southwest part of the basin, which increase in thickness towards a source area located along the southwest margin of the basin. The sedimentary facies represent deposition on a vast alluvial plain with lateral and downstream accretionary sand bodies in fluvial channels and floodbasin and subordinate lacustrine muds and silts in the extensive interchannel areas. Biostratigraphically, the Abrahamskraal Formation falls within the Tapinocephalus Assemblage Zone. However, along the southwestern margin of the basin, this zone is underlain by the Eodicynodon Assemblage Zone.
... This small herbivorous, long-bodied and short-legged, non-mammalian synapsid was, at times, a common inhabitant of the Permian floodplains of the Karoo yet at other times Diictodon was much rarer (e.g. Day et al., 2015;Keyser and Smith, 1979;Smith et al., 2012). Smith (1993) used systematic prospecting of continuous cliff section outcrops to assess the taphonomic and sedimentological biases that influenced bone burial and preservation in the various floodplain facies of the Hoedemaker Member. ...
... Therefore, the relative abundance of the various fossil taxa preserved in this facies should more closely reflect their relative abundance in the once-living community. Keyser and Smith (1979) conducted systematic fossil prospecting aimed at quantifying the relative abundance of fossils of all but the rarest taxa in each of the lower Beaufort biozones. Through this work they were able to highlight examples of collector bias in the South African collections. ...
In the late 1980's the discovery of late Permian helical burrow casts containing articulated skeletons of the small herbivorous therapsid Diictodon feliceps led to conjecture that they may have been used for oviposition/parturition and shelter for infants. Here we present new fossil evidence in support of this interpretation and discuss the possibility that some of the burrows were specially excavated as brood chambers. A re-investigation of the original helical burrow site recovered several more burrow casts containing scattered yet still-associated skeletons of Diictodon. Mechanical preparation of a complete terminal chamber revealed a disarticulated but anatomically-associated adult Diictodon skeleton along with a single tiny (5 mm long) humerus of an infant dicynodont. Nearby outcrops yielded a second association of an adult Diictodon skull (skull length 93 mm) on top of a tiny semi-articulated Diictodon skull and skeleton (skull length 19 mm) with a second infant mandible and a skeleton of the gracile therocephalian Ictidosuchoides longiceps. Synchrotron imaging of this putative burrow-fill confirmed that the humeral morphology of the infant skeleton closely matches the tiny humerus in the unequivocal burrow cast. The common occurrence of Diictodon remains within the casts, combined with their specialized limbs for digging and histological data that indicates uninterrupted growth to ca. 70% of adult size, strongly suggests that they dug underground primarily for thermo-regulation. Moreover, our new fossil evidence of behaviourally-associated neonate and adult Diictodon within these structures indicates that the terminal portions of underground burrows were facultatively used as brood chambers.
... Tetrapod fossils were not considered to be present in the immediately underlying strata of the Ecca Group (Hatch and Corstorphine, 1909), but several tetrapod fossil discoveries in the early 20th Century in strata that were attributed to the Ecca appeared to refute this (Broom 1905, Broom 1913, Brink and Kitching, 1951 [see Rossouw (1955) regarding the latter], Kingsley, 1977). The biostratigraphic position of these fossils was at first uncertain but later biostratigraphers, including Kitching (1977) and Keyser and Smith (1978) accepted the Tapinocephalus or Dinocephalian Assemblage Zone as the lowermost biozone of the Beaufort Group, with its lower boundary corresponding to the contact between the Waterford Formation (Ecca Group) and Abrahamskraal Formation (Beaufort Group) (Keyser and Smith, 1978). At that stage the contact between the Ecca and Beaufort groups was taken at the first maroon mudrocks (Haughton et al., 1953;Mountain, 1946, Rossouw andDe Villiers, 1952). ...
... Tetrapod fossils were not considered to be present in the immediately underlying strata of the Ecca Group (Hatch and Corstorphine, 1909), but several tetrapod fossil discoveries in the early 20th Century in strata that were attributed to the Ecca appeared to refute this (Broom 1905, Broom 1913, Brink and Kitching, 1951 [see Rossouw (1955) regarding the latter], Kingsley, 1977). The biostratigraphic position of these fossils was at first uncertain but later biostratigraphers, including Kitching (1977) and Keyser and Smith (1978) accepted the Tapinocephalus or Dinocephalian Assemblage Zone as the lowermost biozone of the Beaufort Group, with its lower boundary corresponding to the contact between the Waterford Formation (Ecca Group) and Abrahamskraal Formation (Beaufort Group) (Keyser and Smith, 1978). At that stage the contact between the Ecca and Beaufort groups was taken at the first maroon mudrocks (Haughton et al., 1953;Mountain, 1946, Rossouw andDe Villiers, 1952). ...
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.
... Kannemeyeriiforms, which formed the major Triassic radiation of dicynodonts, also first appear in the African record in the Cynognathus AZ (Keyser and Cruickshank, 1979). Within the Cynognathus AZ, a highly characteristic fauna has long been recognized, consisting of the eucynodonts Cynognathus and Diademodon and the kannemeyeriiform Kannemeyeria (Keyser and Smith, 1978;Keyser, 1979;Kitching, 1984;. The shared presence of these three taxa in other basins has been used to correlate the Cynognathus AZ with other Gondwanan faunas, namely, the Smith, 2009), the Manda Beds in Tanzania (Cruickshank, 1965;Wynd et al., 2018), and the lower Ntawere Formation in Zambia (Brink, 1963;Angielczyk et al., 2014;Peecook et al., 2018). ...
... Although the Cynognathus-Diademodon-Kannemeyeria assemblage was historically considered to range throughout Cynognathus AZ rocks in South Africa (Keyser and Smith, 1978), beginning in the 1990s more detailed stratigraphic research began to question the uniformity of this assemblage zone (although Cynognathus does seem to be present throughout; see Abdala et al., 2005b). Hancox et al. (1995) proposed division of the Cynognathus AZ into three subzones (informally labeled A, B, and C) based on temnospondyl distribution and argued that most of the known Cynognathus, Diademodon, and Kannemeyeria material from South Africa pertains to Subzone B. Subsequent research has supported the faunal distinction between these subzones. ...
A new taxon of kannemeyeriiform dicynodont, Ufudocyclops mukanelai, is described based on a well-preserved skull from Subzone C of the Cynognathus Assemblage Zone, which are the youngest strata (probably Middle Triassic) of the Beaufort Group (uppermost Burgersdorp Formation) in South Africa. Ufudocyclops mukanelai is diagnosed by its autapomorphic intertemporal morphology: the intertemporal bar in this taxon is ‘X’-shaped—broad anteriorly and posteriorly but distinctly ‘pinched’ at mid-length and bears a deep, triangular depression immediately behind the enormous pineal foramen. The new kannemeyeriiform can also be diagnosed by the presence of a laterally expanded jugal plate beneath the orbit, and highly discrete, ovoid nasal bosses separated by a broad, unornamented median portion of the premaxilla and the nasals. Two partial dicynodont skulls from this subzone, previously identified as specimens of the otherwise Tanzanian taxon Angonisaurus, are also referable to U. mukanelai. Removal of these specimens from the hypodigm of Angonisaurus eliminates a crucial point of correlation between Cynognathus Subzone C and the Manda Beds of Tanzania and suggests that Subzone C preserves a distinct, endemic fauna, not just a southern extension of the better-known Middle–Late Triassic tetrapod faunas from Tanzania and Zambia. Inclusion of Ufudocyclops in a phylogenetic analysis of anomodonts recovers it as an early stahleckeriid, the first record of this clade from the Cynognathus Assemblage Zone.
... Smith (1995) first described a Permian-Triassic boundary section from what has been referred to in the literature as the Bethulie locality in the Free State Province. At that point in time, the stratigraphic ranges of the Daptocephalus (Dicynodon) and Lystrosaurus AZ faunas were thought to be non-concurrent (Keyser, 1981;Keyser and Smith, 1978), even though Hotton (1967) reported overlap in the stratigraphic ranges of the index taxa. This latter observation was confirmed by the biostratigraphic ranges presented by Smith (1995, his Fig. 3). ...
... Yet, vertebrate ranges still are considered sufficient for the identification of three extinction and one "early recovery" phases in the boundary interval. Kitching (1971Kitching ( , 1977 was the first to circumscribe the Daptocephalus Zone which was renamed, shortly thereafter, as the Dicynodon lacerticeps AZ by Keyser and Smith (1978). These authors considered Daptocephalus to represent a junior synonym of Dicynodon lacerticeps and later researchers, following the scheme in Rubidge (1995), referred to the Dicynodon AZ in subsequent PTB studies (Smith, 1995;Ward et al., 2000Ward et al., , 2005Smith and Botha-Brink, 2014). ...
The stratigraphic section at Bethulie, South Africa, is reported to contain the vertebrate-defined Permian–Triassic boundary succession in the terrestrial realm of the Karoo Basin. The model of vertebrate turnover, from the Daptocephalus to Lystrosaurus Assemblage Zones, tightly constrains the boundary sequence to a short stratigraphic interval where siltstone color begins to change from greenish gray to grayish red, the latter color interpreted to be a consequence of aridification. The biological response to this facies change has been termed “the Great Dying,” and the sedimentary rocks that are preserved are ascribed to a playa lake depositional setting. This drying event is believed to be contemporaneous across the basin, although previous studies have shown that the facies appears at multiple horizons at all purported Permian–Triassic boundary sections in the basin.
... As the uppermost 30 m of the Palingkloof Member is exposed on Maanhaar, the Permo-Triassic boundary may be located some 5-10 m below the base of the koppie. The Early Triassic age of the Barendskraal exposures is supported by the presence of characteristic pedogenic horizons, subvertical Taenidium invertebrate burrow casts, and the vertebrate taxa Lystrosaurus, Prolacerta and Proterosuchut>, all of which are typical of Early Triassic Lystrosaurus Assemblage Zone deposits of the Karoo Basin (Kitching 1977;Keyser & Smith 1979;Smith & Ward 2001). ...
... Fairydale, Bethulie District) in which strata of both the Palingkloof Member and Katberg Formation are exposed (Kitching 1977;Smith & Ward 2001). Nevertheless, fossils of Procolophon appear to be rare in the lower part of the Lystrosaurus Assemblage Zone, but increase in abundance toward the upper reaches of the biozone (Keyser & Smith 1979;Neveling 2002). On the other hand, there is no evidence for the occurrence of the basal procolophonoid Owenetta in the upper part of the Lystrosaurus biozone (contra , whereas its presence in the lower part of the biozone, as postulated by Kitching (1977), is now firmly established by its occurrence in the PalingkloofMember at Barendskraal (Fig. 1 ). ...
A diverse amniote fauna has been recovered from Lower Triassic Lystrosaurus Assemblage Zone exposures on the farm Barendskraal, near Middelburg in Eastern Cape Province, South Africa. The fauna includes the dicynodont therapsid Lystrosaurus sp., the therocephalian therapsids Tetracynodon darti, Moschorhinus kitchingi and Ericiolacerta parva, the archosauromorph reptiles Proterosuchus fergusi and Prolacerta broomi, and the procolophonoid reptiles Owenetta kitchingorum, Sauropareion anoplus and Saurodectes rogersorum. The locality is remarkable in that although it is fossil-rich, Lystrosaurus fossils do not appear to be as abundant as elsewhere in this assemblage zone, and the diversity of taxa at Barendskraal (at least nine species) is surpassed only by that of the famous Harrismith Commonage locality in the northeastern Free State province (at least 13 species). However, the fauna at Harrismith Commonage is typical of most other Lystrosaurus biozone localities in being dominated numerically by Lystrosaurus. Study of the tetrapod taxa from Barendskraal is providing new insights into procolophonoid phylogeny and survivorship across the Permo-Triassic boundary, as well as the stratigraphic ranges of various taxa in the Lower Triassic deposits of the Karoo Basin.
... 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.
... In their vertebrate biozonation of the Western Karoo Basin, Keyser & Smith (1979) proposed re-naming Boonstra's lower and middle Tapinocephalus AZ together as the Dinocephalian zone, for which both Bradysaurus bombidens and Embrithosaurus schwarzi were designated as characteristic fossil taxa. Both genera were considered to also be present in the overlying Pristerognathus/Diictodon AZ, though at much lower abundance. ...
Pareiasaurs were relatively abundant, globally distributed, herbivorous parareptiles of the mid to late Permian. The basal-most forms, all members of the Bradysauria, are restricted to the Guadalupian (mid-Permian) of South Africa and went extinct in the late Capitanian near the top of the Tapinocephalus Assemblage Zone. Currently four species are recognised in this group: Bradysaurus seeleyi, B. baini, Embrithosaurus schwarzi and Nochelesaurus alexanderi. Those taxa have historically been poorly defined and based on a limited number of specimens, leaving the taxonomic diversity of the group open to doubt and limiting their utility in biostratigraphy. Here we present our fourth and final contribution designed to improve the understanding of this group of pareiasaurs by providing a taxonomic and phylogenetic review, updated stratigraphic ranges and updated diagnoses for each taxon of the Bradysauria. Bradysaurus seeleyi is synonymised with Bradysaurus baini, resulting in three valid mid-Permian pareiasaur taxa: Bradysaurus baini, Embrithosaurus schwarzi and Nochelesaurus alexanderi. Our cladistic analysis of cranial and postcranial characters supports the monophyly of Bradysauria with five synapomorphies. Embrithosaurus schwarzi is recovered as the sister taxon to a clade containing Bradysaurus baini and Nochelesaurus alexanderi. By identifying 157 pareiasaur specimens in fossil collections we show that the Bradysauria are stratigraphically restricted to the Abrahamskraal Formation of the Beaufort Group and suggest a staggered appearance. Bradysaurus baini is first to appear, followed by Nochelesaurus alexanderi, and lastly by Embrithosaurus schwarzi. All three taxa perished during the Capitanian mass extinction, and have their highest occurrences near the top of the Abrahamskraal Formation.
Keywords: Bradysauria; Capitanian; Guadalupian; Pareiasauria; Tapinocephalus Assemblage Zone.
... Vertebrate assemblage zones were assigned either to the Permian or Triassic based on early-twentieth century interpretations of Broom (1906Broom ( , 1911. These assemblage zones were used by numerous workers (e.g., Keyser and Smith, 1978;Rubidge, 1995) during a time when no numerical age information existed for the rocks in the basin. That condition has changed in the past decade, and the ages of several biozones are now better defined by high-resolution, U-Pb chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) zircon ages (Rubidge et al., 2013;Day et al., 2015;Gastaldo et al., 2015Gastaldo et al., , 2020a. ...
The contact between the Daptocephalus to Lystrosaurus declivis (previously Lystrosaurus) Assemblage Zones (AZs) described from continental deposits of the Karoo Basin was commonly interpreted to represent an extinction crisis associated with the end-Permian mass-extinction event at ca. 251.901 ± 0.024 Ma. This terrestrial extinction model is based on several sections in the Eastern Cape and Free State Provinces of South Africa. Here, new stratigraphic and paleontologic data are presented for the Eastern Cape Province, in geochronologic and magnetostratigraphic context, wherein lithologic and biologic changes are assessed over a physically correlated stratigraphy exceeding 4.5 km in distance. Spatial variation in lithofacies demonstrates the gradational nature of lithostratigraphic boundaries and depositional trends. This pattern is mimicked by the distribution of vertebrates assigned to the Daptocephalus and L. declivis AZs where diagnostic taxa of each co-occur as lateral equivalents in landscapes dominated by a Glossopteris flora. High-precision U-Pb zircon (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) age results indicate maximum Changhsingian depositional dates that can be used as approximate tie points in our stratigraphic framework, which is supported by a magnetic polarity stratigraphy. The coeval nature of diagnostic pre- and post-extinction vertebrate taxa demonstrates that the L. declivis AZ did not replace the Daptocephalus AZ stratigraphically, that a biotic crisis and turnover likely is absent, and a reevaluation is required for the utilization of these biozones here and globally. Based on our data set, we propose a multidisciplinary approach to correlate the classic Upper Permian localities of the Eastern Cape Province with the Free State Province localities, which demonstrates their time-transgressive nature.
... Boonstra (1969) went further and suggested that very few species were present in the uppermost part of the Tapinocephalus AZ and that pareiasaurs and dinocephalians were not present at all. In their stratigraphic review of the Beaufort Group, Keyser and Smith (1978) detached these uppermost strata and recognized the extinction of the dinocephalians as the upper boundary of their Dinocephalian AZ, which they correlated with a chert horizon about 120 m below the base of the Poortjie Member (Teekloof Formation). Smith and Keyser (1995) considered the top of the Dinocephalian AZ, then renamed the Tapinocephalus AZ, to occur closer to the base of the Poortjie Member, and it was this horizon that was first linked with Capitanian mass extinction (Retallack et al., 2006). ...
The Beaufort Group of the main Karoo Basin of South Africa records two major extinction events of terrestrial vertebrates in the late Palaeozoic. The oldest of these has been dated to the late Capitanian and is characterized by the extinction of dinocephalian therapsids and bradysaurian pareiasaurs near the top of Tapinocephalus Assemblage Zone. Faunal turnover associated with the extinction of dinocephalians is evident in vertebrate faunas from elsewhere in Pangaea but it can be best studied in the Karoo Basin, where exposures of the upper Abrahamskraal and lower Teekloof formations allow continuous sampling across the whole extinction interval. Here we present field data for several sections spanning the Capitanian extinction interval in the southwestern Karoo and discuss recent work to establish its timing, severity, and causes. A large collections database informed by fieldwork demonstrates an increase in extinction rates associated with ecological instability that approach that of the end-Permian mass extinction, and shows significant turnover followed by a period of low diversity. Extinctions and recovery appear phased and show similarities to diversity patterns reported for the end-Permian mass extinction higher in the Beaufort sequence. In the Karoo, the late Capitanian mass extinction coincides with volcanism in the Emeishan Large Igneous Province and may have been partly driven by short-term aridification, but clear causal mechanisms and robust links to global environmental phenomena remain elusive.
... Recent vertebrate palaeontological studies on the K5 Formation confirmed the previous findings, and revealed a new Endothiondon species (Macungo et al. 2020) and a new dicynodont species Niassodon mfumukasi (Castanhinha et al. 2013). According to the zonation of Keyser and Smith (1978), these can be correlated either with the Tropidostoma-Endothiodon or the Aulacephalodon-Cistecephalus assemblage zone of the lower Beaufort Group of South Africa. A diagenetic concretion collected from the K5 Formation was sampled for U/Pb geochronology, and the age obtained was 258 ± 10 Ma, indicating a Lopingian (late Permian) age (Norconsult Consortium 2007). ...
... Broom (1906) was the first to assign specimens of Lystrosaurus to the Triassic and placed the underlying biozones, including the interval now encompassing the Daptocephalus AZ (Viglietti et al., 2016), into the Late Permian. His sixfold biozonation (Broom, 1911) was revised by Kitching (1971Kitching ( , 1977, with subsequent modifications by Keyser and Smith (1978) and Keyser (1979), and were accepted by the South African Committee for Stratigraphy as formal nomenclature (South African Committee for Stratigraphy [SACS], 1980). Subsequently, this nomenclature was expanded (Rubidge, 1995) to an eightfold biozonation system and, again, refined during a recent review . ...
The stable carbon- and oxygen-isotope values derived from in situ pedogenic carbonate-cemented nodules and vertebrate apatite in the Daptocephalus and overlying Lystrosaurus Assemblage Zones of the Balfour Formation, Karoo Basin, South Africa, have formed the basis for previous interpretations of a unidirectional climate trend toward hyper-aridity across the biozone boundary. This assemblage-zone boundary has been considered by many authors to be equivalent to the Permian–Triassic boundary in the basin. To better understand the climate under which these vertebrate assemblages existed, we have analyzed the carbon- and oxygen-stable isotopes of pedogenic carbonate nodules sampled from fourteen horizons of intraformational pedogenic nodular conglomerate (PNC) at Old Lootsberg Pass, a classic locality at which the Permian–Triassic boundary is reported. Analysis of these refractory soil constituents provides insight into the climate under which these “ghost” soils formed, where no other physical record of their existence is found in the stratigraphy. A positive correlation between δ¹³CVPDB and δ¹⁸OVSMOW values of micrite cements is defined by analyses of carbonate nodules taken from a measured stratigraphic thickness of ∼200 m, which spans the biozone boundary as currently defined. For samples taken from the same lag deposit, similar and relatively narrow ranges of isotope values are encountered. Samples cluster into two isotopic groups. The values in the first group cluster more tightly in all sampled nodules (δ¹³CVPDB −2.3 to −6.5‰; δ¹⁸OVSMOW 13.8–15.1‰), and are interpreted to indicate that these originated from paleosols that formed under similar climate controls. Values from the second sample group display a wider variance between analyses (δ¹³CVPDB −5.2 to 14.0‰; δ¹⁸OVSMOW 8.8–15.5‰). These nodules are interpreted to indicate that they originated under polygenetic soil-forming conditions representing the reworking of either: (1) more than one paleosol, the calcite-cemented nodules of which represent precipitation under both closed and open-system controls; or (2) one or more compound-composite paleosols. Stable-isotope trends based on PNCs analyzed, thus far, demonstrate an overall shift over time in the ghost landscapes. More seasonally dry soils formed under a climate that can be characterized as warm/dry accompanied by lower precipitation in the lower part of the section. In contrast, soils in the upper part of the section formed under cool and moist conditions, with increased precipitation near the biozone boundary. Hence, latest Permian climate associated with the more seasonally dry landscapes demonstrate a trend toward cooler and wetter conditions, which is opposite to the trend widely held in the literature.
... 5a), Sangusaurus parringtonii (e.g., Angielczyk et al., 2018), and Kannemeyeria simocephalus (e.g., Renaut, 2000). Hammer (1995) originally correlated the fauna of the upper Fremouw Formation to the Cynognathus Assemblage Zone of the South African Beaufort Group, which has long been characterized by the presence of the eucynodonts Cynognathus and Diademodon, and the kannemeyeriiform dicynodont Kannemeyeria (Keyser and Smith, 1978;Rubidge, 1995;Kammerer et al., 2019). This was based primarily on the presence of AMNH FARB 24403, as well as material referred to Cynognathus and Diademodontidae (Hammer, 1995). ...
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.
... The extensive records of well-preserved terrestrial fossil vertebrate biozones that establish temporal-spatial resolution for the fluvio-deltaic Beaufort Group (Keyser and Smith, 1979;Kitching, 1977;Rubidge, 1995;Smith and Keyser, 1995) is unfortunately not achievable for the lacustrine to marine Ecca Group. The Ecca Group is characterized by few age-diagnostic fossils and generally poorly preserved palynomorphs due to marine conditions (Visser, 1989(Visser, , 1997, metamorphic effects of the Cape Fold Belt and thermal effects of dolerite intrusions that are related to extrusion of the Drakensberg Group (Barbolini et al., 2018). ...
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.
... This concept was expanded by Broom (1906aBroom ( , 1906bBroom ( , 1907Broom ( , 1909, who proposed a six-fold biostratigraphic zonation for the Beaufort Group based on genera that, with slight modification (Hotton and Kitching 1963), was accepted by most for the next sixty years (Von Huene 1925;Du Toit 1954). Subsequent collecting in the Karoo Basin allowed for further revision of the Beaufort biostratigraphy (Kitching 1970, 1977, Keyser and Smith 1979Keyser 1979;SACS 1980) and included the Elliot and Clarens formations of the upper Stormberg Group (Kitching and Raath 1984). In 1995, BSR edited a multi-authoured volume commissioned by the South African Commission for Stratigraphy that formalised the Beaufort Group biozones as assemblage zones defined by the co-occurrence of three or more index taxa, but for simplicity named after only one (Rubidge 1995). ...
... Petrographic studies have shown that siliciclastic rocks can be used to identify the source area (provenance) as well as related geological processes responsible for deposition (Basu et al., 1975;Dickinson et al., 1983;Johnson, 1991;Bordy et al., 2004). Studies of the Balfour Formation were carried out by Johnson (1976Johnson ( , 1991, Keyser and Smith (1978), Kitching (1977Kitching ( , 1995, Visser and Dukas (1979), Smith (1995), Haycock et al. (1997), Hiller and Stavrakis (1984), Rubidge et al. (2000) and Catuneanu and Elango (2001) from various angles viz. Paleontology, stratigraphy, sedimentology and lithofacies but despite these studies, the mineralogical compositions of these sediments and their sources are still poorly understood. ...
... Anderson and Cruickshank (1978) referred to it as the 'Kannemeyeria/Diademodon empire' of the Karoo and drew correlations to the lower Ntawere assemblage. Kitching (1984) referred to it as the Cynognathus-Diademodon Assemblage Zone and Keyser and Smith (1978) as the Kannemeyeria-Diademodon Assemblage Zone. The 'empire' was the most productive region of the CAZ, subzone B, and all the vertebrate assemblages that correlated with it via the shared presence of Cynognathus, Diademodon, and/or Kannemeyeria (Kitching, 1977;Hancox et al., 1995;Rubidge, 2005, Smith et al., 2012. ...
The two vertebrate fossil assemblages from the ?Middle Triassic Ntawere Formation have been known since the 1960s, but little new work has been done since the description of novel taxa in the 1960s and 1970s. Three recent field seasons have increased vertebrate diversity in the upper Ntawere assemblage and expanded biostratigraphic connections between the lower and upper Ntawere assemblages and assemblages in fossiliferous basins across southern Pangea. The upper Ntawere contains hybodontoid sharks, ptychoceratodontid lungfish, large- and small-bodied stereospondyl amphibians (Cherninia, ‘Stanocephalosaurus,’ Batrachosuchus, a new taxon), stahleckeriid dicynodonts (Sangusaurus, Zambiasaurus), traversodontid and trirachodontid cynodonts (Luangwa, a new species, Cricodon), and at least four archosauromorphs, including a large loricatan pseudosuchian, a shuvosaurid poposauroid, and silesaurid dinosauriforms (Lutungutali), whereas the lower Ntawere contains the cynodonts Cynognathus and Diademodon and species of the dicynodont Kannemeyeria. The lower and upper Ntawere assemblages have been correlated with the middle and upper subzones of the Cynognathus Assemblage Zone of the Karoo Basin, South Africa, into a network of connections between assemblages in modern day Tanzania, Argentina, Brazil, Namibia, Antarctica, and India. Although lower Ntawere correlations are reinforced by the occurrence of Cynognathus, new observations from the upper Ntawere, in combination with field work in Tanzania, Namibia, and Brazil, have shifted the geographic focus of biostratigraphic connection away from the Karoo later in the Triassic. A recent radiometric date from Argentina from below the horizon correlated with both the Karoo and the lower Ntawere places these, and all higher assemblages, into the Carnian Stage of the Late Triassic.
Citation for this article: Peecook, B. R., J. S. Steyer, N. J. Tabor, and R. M. H. Smith. 2018. Updated geology and vertebrate paleontology of the Triassic Ntawere Formation of northeastern Zambia, with special emphasis on the archosauromorphs; pp. 8–38 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).
... The lack of extensive limb material available for Seeley's (1895) original description set the stage for confusion between Cynognathus and another large-bodied cynognathian, Diademodon tetragonus, found in the same beds (Seeley, 1894;Brink, 1963;Kitching, 1977Kitching, , 1995Keyser and Smith, 1979). Although apomorphies of each genus can be recognized, they are exclusively craniodental (i.e., shape of the postcanine teeth or lambdoidal crest), with much of the remaining postcranial anatomy considered to be remarkably similar (Jenkins, 1971;Hopson and Kitching, 1972;Martinelli et al., 2009). ...
Cynognathus crateronotus is a species of large carnivorous cynodont, first named and best known from the Triassic Burgersdorp Formation (Beaufort Group, Karoo Basin) of South Africa. Fossils of the genus have also been reported from the upper Fremouw Formation of Antarctica, the Upper Omingonde Formation of Namibia, and the Río Seco de la Quebrada Formation of Argentina. Without associated cranial material, however, distinguishing the postcrania of Cynognathus from that of the closely related cynognathian, Diademodon tetragonus, has proven difficult. Here we provide a more comprehensive diagnosis for Cynognathus crateronotus and describe two novel occurrences. First, parts of a medium-sized individual were recovered from a scrambled mass of dental and semiarticulated postcranial material from the lower Ntawere Formation of Zambia, a horizon that previously produced fossils of Diademodon and Kannemeyeria. Second, a large individual was collected from a recently discovered locality within the lower part of the Lifua Member of the Manda Beds of Tanzania. A large proportion of the postcranial skeleton, along with some craniodental remains, was found ex situ in a sandy streambed just downstream from a quarry that has produced the dicynodont Dolichuranus, an azendohsaurid archosauromorph, and the avemetatarsalian Teleocrater rhadinus. The widespread occurrence of Cynognathus across southern Pangea demonstrates its utility as a biostratigraphic marker, but recently published radiometric age estimates from Argentina suggest that either the genus persisted for over 10 million years or African strata traditionally interpreted as Middle Triassic are better understood as Late Triassic in age.
Citation for this article: Wynd, B. M., B. R. Peecook, M. R. Whitney, and C. A. Sidor. 2018. The first occurrence of Cynognathus crateronotus (Cynodontia: Cynognathia) in Tanzania and Zambia, with implications for the age and biostratigraphic correlation of Triassic strata in southern Pangea; pp. 228–239 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).
... It comprises repetitive sandstone and mudrock-rich intervals that vary in lateral and vertical distribution and thickness and were deposited by very large (>500 km) continental fluvial systems (Smith, 1993;Smith et al., 1993;Catuneanu et al., 1998;Catuneanu and Elango, 2001). Most geological research on the Beaufort Group has focussed on the sedimentology of stratabound uranium occurrences (Kubler, 1977;Turner, 1985;Cole and Wipplinger, 2001) and its eight vertebrate biozones defined by the stratigraphic distribution of synapsid and other tetrapod fauna for which the Beaufort Group is world renowned (Keyser, 1979;Keyser and Smith, 1979;Rubidge et al., 1995;Day, 2013;Viglietti et al., 2016). Biozones have highlighted two significant faunal turnovers in the Beaufort Group co-incident with the end-Guadalupian (Day et al., 2015) and end-Permian extinction events (Smith, 1995;Botha and Smith, 2006;Smith et al., 2012;Botha-Brink et al., 2014;Smith and Botha-Brink, 2014;Gastaldo et al., 2015). ...
... The bathymetric conditions of this interior seaway changed from deep marine during the Dwyka-lower Ecca interval, to shallow marine during the upper Ecca time (Visser and Lock, 1978). Biostratigraphic correlations across the main Karoo Basin using palynomorphs in the Ecca Group (McRae, 1992) and vertebrate fossils in the Beaufort Group (Kitching, 1977;Keyser and Smith, 1979) have highlighted the diachroneity of most of the lithostratigraphic units within these strata. ...
Basin subsidence analysis, employing the backstripping method, indicates that fundamentally two different basin-generating mechanisms controlled Tanqua depocentre development in SW Karoo Basin. The subsidence curves display initial dominantly decelerating subsidence, suggesting an extensional and thermal control possibly in a strike-slip setting during the depocentre formation. Subsequent accelerating subsidence with time, on the other hand, suggests that the dominant control on the depocentre formation in SW Karoo was flexure of the lithosphere. Based on these observations on the subsidence curves, it is, therefore, possible to recognise the first stage of positive inflexion (~ 290 Ma) as the first stage of Tanqua depocentre formation.
Petrographic study shows that most of the studied sandstones of the Tanqua depocentre at depth of ~ 7.5 Km were subjected to high pressure due to overlying sediments. They are tightly-packed as a result of grain adjustment made under such pressure and eventually the development of sutured contacts. It is clear that compaction (i.e. grain deformation and pressure solution) occurred on the sediments. This led to total intergranular porosity reduction of the quartz-rich sediments and dissolution of the mineral grains at intergranular contacts under non-hydrostatic stress and subsequent re-precipitation in pore spaces.
Furthermore, siliciclastic cover in the Tanqua depocentre expanded from minimal values in the early Triassic (Early to Late Anisian) to a maximum in the middle Permian (Wordian -Roadian). This accompanied a global falling trend in eustatic sea-level and favoured by a compressional phase involving a regional shortening due to orogenic thrusting and positive inflexions (denoting foreland basin formation). The estimate of sediment volume obtained in this study for the Permian Period reached a maximum in the middle Permian and is, therefore, consistent with published eustatic sea-level and stress regime data. This new data are consistent with a diachronous cessation of marine incursion and closure of Tanqua depocentre, in relation to a compressional stress regime in Gondwana interior during the late Palaeozoic.
... The origin of this scheme can be traced to that of Broom (1906), who proposed a sixfold subdivision and presumed the Lystrosaurus beds (i.e., the Lystrosaurus AZ in the modern scheme) to be Early Triassic in age; all preceding units were considered Permian. The assignment of these lower biozones, of which the Dicynodon Assemblage Zone (AZ) is the youngest (Keyser and Smith 1978), received wide acceptance (Rubidge 1995;Rubidge et al. 2013). In contrast, the Triassic age of the Lystrosaurus AZ had been questioned, but most workers by the 1980s, agreed with its assignment to the earliest Triassic (see summary in Neveling 2004). ...
The Karoo Basin has long been considered to contain the type stratigraphic succession for the terrestrial expression of the end-Permian mass extinction. A detailed extinction model, based on biostratigraphic and geologic data, has proposed rapid environmental change that coincides with a vertebrate biozone boundary, which was postulated to have been caused by increased aridity. Our sedimentologic, geochronologic, palaeomagnetic, and geochemical data collected from reported boundary sections, show that the link between the floral and faunal turnover and marine end-Permian event is tenuous. A review of existing, as well as our own palaeontological data, interpreted within a robust stratigraphic and sedimentologic framework, further indicate that ecological change was more subtle and protracted than currently modeled, and reflects the complex way in which the ancient Karoo landscape responded to changes in several extrinsic factors.
... Petrographic studies have shown that siliciclastic rocks can be used to identify the source area (provenance) as well as related geological processes responsible for deposition (Basu et al., 1975;Dickinson et al., 1983;Johnson, 1991;Bordy et al., 2004). Studies of the Balfour Formation were carried out by Johnson (1976Johnson ( , 1991, Keyser and Smith (1978), Kitching (1977Kitching ( , 1995, Visser and Dukas (1979), Smith (1995), Haycock et al. (1997), Hiller and Stavrakis (1984), Rubidge et al. (2000) and Catuneanu and Elango (2001) from various angles viz. Paleontology, stratigraphy, sedimentology and lithofacies but despite these studies, the mineralogical compositions of these sediments and their sources are still poorly understood. ...
... Kitching (1977) used Da. leoniceps as the index fossil for the original manifestation of the biozone (called the Daptocephalus Zone in that paper), which was only renamed Dicynodon Assemblage Zone by Keyser and Smith (1979) because of the assumed synonymy of Daptocephalus with Dicynodon (Cluver and Hotton, 1981). Now that Daptocephalus has been resurrected, the original name of this unit should be restored. ...
... In this framework, the ''unproductive'' values represent areas covered with soil or vegetation, areas with no relief, or unsampled areas (see King 1991 for details). There are potential problems with the outcrop data provided by King (1991): First, the total outcrop data was collected from a relatively low-resolution map with the assemblage zone boundaries of Keyser and Smith (1979) superimposed on it. Second, the total outcrop values include areas where the Beaufort Series is overlain by Cenozoic rocks or soil. ...
This study investigates diversity patterns of Synapsida in the Permian-Triassic sequence of the Karoo Basin, South Africa. Permian-Triassic synapsids represent the dominant terrestrial tetrapods of their time and play a central role in assessing the impact of the end-Permian mass extinction on terrestrial ecosystems. On the regional scale of the Karoo Basin, synapsid diversity shows a mid-Permian extinction and a pronounced extinction event at the end of the Permian, whereas the subclades of Synapsida exhibit clade-specific diversity patterns. Taxonomic diversity estimates (TDEs) of Synapsida and its subclades are not significantly correlated with outcrop area for the complete time series. However, after exclusion of the Lystrosaurus Assemblage Zone from all data series, the TDEs of the majority of synapsid subclades show statistically significant strong positive correlations with outcrop area. Nonetheless, diversity residuals, resulting from modeled diversity estimates, exhibit clade-specific patterns with varying support for a mid-Permian event and strong support for an end-Permian extinction. The results confirm studies at the global scale and imply that synapsid diversity in the Karoo Basin is at least partially biased by the Permian-Triassic terrestrial rock record. Moreover, Anomodontia, the most speciose clade of non-mammalian synapsids, is not the sole driver of the synapsid diversity signal. Instead, there seems to be a general synapsid pattern, with each subclade diverging from this pattern to varying degrees for clade-specific reasons. Thus, despite the obvious rock record bias, the end-Permian extinction maintains its major impact on synapsid diversity and therefore on the composition and structure of past and present terrestrial ecosystems.
The Cynognathus Assemblage Zone (AZ) has been recognized for more than 100 yr and is one of the most durable tetrapod biostratigraphic concepts of the Triassic. Long treated as a single biostratigraphic unit, the Cynognathus AZ is now divided into three subzones (in ascending order), A, B and C. The South African Cynognathus AZ can be correlated across Pangea to tetrapod assemblages in Algeria, and Zambia. Various index taxa found in the subzones of the Cynognathus AZ in the Karoo basin provide multiple and reinforcing correlations, and independent age constraints combined with marine records of Parotosuchus associated with ammonoids indicate that subzone A is of Olenekian age, primarily Spathian, but perhaps as old as part or all of the Smithian. The early Anisian age of subzone B lacks robust support and is largely based on its stratigraphic position in the Karoo basin between late Olenekian (subzone A) and late Anisian (subzone C) assemblages. In China a subzone B assemblage of the lower Ermay-ing Formation is overlain by a late Anisian assemblage of the upper Ermaying Formation correlative to sub-zone C. The Russian Eryosuchus fauna, which is very likely of Anisian age, is at least in part correlative with subzone B, and palynostratigraphy in Australia also indicates an Anisian age for strata (Ashfield Slate) that contain subzone B and C tetrapods. Correlation of subzone C to the later Anisian is primarily supported by a radioisotopic age from China that indicates a subzone C tetrapod assemblage is ~ 243 Ma. The beginning of Perovkan time is close to the beginning of the Anisian, so the Nonesian is the time equivalent to subzone A, and subzones B and C are of Perovkan age. Nevertheless, how close the base of subzone B of the Cynognathus AZ may be to the base of the Anisian is not clear, and a stronger basis is needed to identify the beginning of the Anisian and the beginning of the Perovkan land-vertebrate faunachron in the time interval represented by subzone B of the Cynognathus AZ.
The Burgersdorp Formation of South Africa is a richly fossiliferous rock sequence at the top of the Permian–Triassic Beaufort Group and is known for its abundance of Early–Middle Triassic vertebrate remains, particularly cynodonts. Fossils from the Burgersdorp Formation are referred biostratigraphically to the Cynognathus Assemblage Zone (CAZ), which is further divided into three subzones: Langbergia - Garjainia, Trirachodon - Kannemeyeria , and Cricodon-Ufudocyclops . Each subzone is characterised by the presence of a distinct species of trirachodontid, a group of gomphodont cynodonts found relatively abundantly throughout the CAZ, with the lower two subzones characterised by the medium-sized trirachodontids Langbergia and Trirachodon . The uppermost part of the formation, the Cricodon-Ufudocyclops subzone, yields trirachodontids of larger size. The majority of these trirachodontid specimens have previously been referred to Cricodon metabolus , a taxon also known from the Manda Beds of Tanzania and the Ntawere Formation of Zambia. Here we identify one of the specimens (BP/1/5538) previously referred to Cricodon as a new taxon, Guttigomphus avilionis . Guttigomphus can be distinguished from other gomphodont cynodonts by features of the upper postcanine teeth, such as an asymmetric crown in occlusal view (crown narrower along the lingual margin than the labial). Our phylogenetic analysis recovers Guttigomphus as a basal member of Trirachodontidae, outside of the clade including Cricodon , Langbergia and Trirachodon .
The Permo‐Triassic vertebrate assemblage zones (AZs) of South Africa's Karoo Basin are a standard for local and global correlations. However, temporal, geographical and methodological limitations challenge the AZs reliability. We analyse a unique fossil dataset comprising 1408 occurrences of 115 species grouped into 19 stratigraphic bin intervals from the Cistecephalus, Daptocephalus, Lystrosaurus declivis and Cynognathus AZs. Using network science tools we compare six frameworks: Broom, Rubidge, Viglietti, Member, Formation, and one suggesting diachroneity of the Daptocephalus/Lystrosaurus AZ boundary (Gastaldo). Our results demonstrate that historical frameworks (Broom, Rubidge) still identify the Karoo AZs. No scheme supports the Cistecephalus AZ, and it probably comprises two discrete communities. The Lystrosaurus declivis AZ is traced across all frameworks, despite many shared species with the underlying Daptocephalus AZ, suggesting that the extinction event across this interval is not a statistical artefact. A community shift at the upper Katberg to lower Burgersdorp formations may indicate a depositional hiatus which has important implications for regional correlations, and Mesozoic ecosystem evolution. The Gastaldo model still identifies a Lystrosaurus and Daptocephalus AZ community shift, does not significantly improve recent AZ models (Viglietti), and highlights important issues with some AZ studies. Localized bed‐scale lithostratigraphy (sandstone datums), and singleton fossils cannot be used to reject the patterns shown by hundreds of fossils, and regional chronostratigraphic markers of the Karoo foreland basin. Metre‐level occurrence data suggests that 20–50 m sampling intervals capture Karoo AZs, unifying the use of metre‐level placements of singleton fossils to delineate biozone boundaries and make regional correlations.
The late Permian (Lopingian) Cistecephalus Assemblage Zone (CiAZ) of the Karoo Supergroup in South Africa has recently been radiometrically-dated to range from 256 to 255 My. It encompasses approximately one million years of the late Wuchiapingian epoch, at a time when the ancient intra-continental lowlands of southern Gondwana had fully recovered from the end-Guadalupian mass extinction. The diverse Cistecephalus Assemblage Zone fauna is dominated by the small herbivorous dicynodonts Diictodon, Pristerodon and the molelike Cistecephalus, along with a range of larger dicynodont herbivores including Oudenodon, Aulacephalodon, Rhachiocephalus, Dinanomodon and rare Endothiodon. The attendant large carnivores include the gorgonopsians Aelurognathus, Rubidgea, and Smilesaurus, while smaller carnivores are represented by eutherocephalians (e.g., Ictidosuchoides, Ictidosuchops) and small gorgonopsians (e.g., Aloposaurus, Scylacocephalus). Of the parareptiles, the large-bodied taxon Pareiasaurus is most common, with the diminutive pareiasaurs Anthodon, Nanoparia, and Pumiliopareia making their first appearance. Lithostratigraphically, the biozone for the most part coincides with the arenaceous Oukloof and lower Steenkampsvlakte members in the western sub-basin and the equivalent Oudeberg and lower Daggaboersnek members in the east, where it reaches its maximum thickness of 300 m. The Cistecephalus Assemblage Zone thins westwards to 120 m at Teekloof Pass, and eastwards to approximately 100 m near the town of Fort Beaufort.
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.
Four substantial tetrapod extinctions have been identified during the Permian, but only one of these is an apparent mass extinction. Analyses of global compilations of the family-level diversity of Permian tetrapods have been confounded by incorrect and compiled correlations. Instead, analyzing diversity patterns at the genus level in “best sections” identifies only one apparent mass extinction of Permian tetrapods. Much evolutionary turnover took place among tetrapods during the latter part of the early Permian and had been identified as a single mass extinction at the Artinskian-Kungurian boundary. However, the only stratigraphically dense tetrapod record of the late early Permian, from the southwestern USA, indicates a succession of extinctions spread out from Redtankian through Littlecrontonian (Kungurian) time, not a single mass extinction. Olson's gap remains a hiatus in the global record of Permian tetrapods equivalent to part of the Kungurian-Roadian. Across the gap, eupelycosaur-dominated assemblages were replaced by therapsid-dominated assemblages, but the claim that this is associated with a mass extinction (“Olson's extinction”) has been based on compressing all of the extinctions of the Redtankian-Littlecrotonian and Olson's gap into one event. Recognition of Olson's gap does not preclude the possibility of an extinction at the early-middle Permian boundary (“Olson's extinction”). However, the gap in the tetrapod fossil record makes it impossible to establish the magnitude, precise timing and structure of the extinctions that took place across Olson's gap.
The most extensive Permian tetrapod (amphibian and reptile) fossil records from the western USA (New Mexico to Texas) and South Africa have been used to define 11 land vertebrate faunachrons (LVFs). These are, in ascending order, the Coyotean, Seymouran, Mitchellcreekian, Redtankian, Littlecrotonian, Kapteinskraalian, Gamkan, Hoedemakeran, Steilkransian, Platbergian and Lootsbergian. These faunachrons provide a biochronological framework with which to assign ages to, and correlate, Permian tetrapod fossil assemblages. Intercalated marine strata, radioisotopic ages and magnetostratigraphy were used to correlate the Permian LVFs to the standard global chronostratigraphic scale with varying degrees of precision. Such correlations identified the following significant events in Permian tetrapod evolution: a Coyotean chronofaunal event (end Coyotean); Redtankian events (Mitchellcreekian–Littlecrotonian); Olson's gap (late Littlecrotonian); a therapsid event (Kapteinskraalian); a dinocephalian extinction event (end Gamkan); and a latest Permian extinction event (Platbergian–Lootsbergian boundary). Problems of incompleteness, endemism and taxonomy, and the relative lack of non-biochronological age control continue to hinder the refinement and correlation of a Permian timescale based on tetrapod biochronology. Nevertheless, the global Permian timescale based on tetrapod biochronology is a robust tool for both global and regional age assignment and correlation. Advances in Permian tetrapod biochronology will come from new fossil discoveries, more detailed biostratigraphy and additional alpha taxonomic studies based on sound evolutionary taxonomic principles.
The dicynodont anomodont Odontocyclops whaitsi , from the Late Permian Madumabisa Mudstone of Zambia, is redescribed and its phylogenetic relationships are considered. The genus is characterized by a two autapomorphies, elongate nasal bosses and a concave dorsal surface of the snout; it also possesses wide exposure of the parietals on the intertemporal skull roof, the presence of a postcaniniform crest, the absence of a labial fossa, and the presence of a dorsal process on the anterior ramus of the epipterygoid footplate. In addition, newly recognized specimens collected in South Africa extend the known geographic range of the genus and allow description of the humerus and scapula for the first time. Cladistic analysis of a data set including Odontocyclops and 18 other well-known South African dicynodont genera does not support the hypothesis that Odontocyclops is a close relative of Dicynodon or of Triassic dicynodonts such as Kannemeyeria. Instead, a close relationship with Oudenodon and Rhachiocephalus is proposed. The presence of Odontocyclops in South Africa and Zambia makes it potentially valuable for more precise biostratigraphic correlation between the sediments of the Karoo Basin and the Luangwa Valley.
Since the first discovery of a fragmentary amphibian jaw at Graphite Peak in 1968 (Barrett et al. 1968), five expeditions have searched for terrestrial vertebrate fossils in the Transantarctic Mountains (Elliot et al. 1970, Colbert 1982, Cosgriff et al. 1978, Hammer et al 1986, 1987). During this interval, 11 productive sites (Fig. 5.1) in the central portion of the range, near the Beardmore and Shackleton Glaciers, have been identified. Other areas explored that have not yielded vertebrates include the Allan Hills near the Dry Valleys of Southern Victoria Land and sections of Northern Victoria Land. (Hammer and Zawiskie 1982, Hammer 1987).
Measured sections through Middle Beaufort sandstones exposed in a shallow syncline to the southwest of East London and again to the northeast of the city, have revealed upper flat-bed lamination with associated primary current lineation to be the dominant sedimentary structure. This is mostly associated with trough cross-bedded units. These and the generally coarse-grained nature of the sandstone, with scattered pebbles, are taken to represent deposition from swift-flowing, shallow, ephemeral braided streams on the distal reaches of an alluvial fan. Typical sequences and facies models based on Markov analysis are presented for the sections. Correlation of these Middle Beaufort sandstones with the Katberg Sandstone of the Winterberg area to the west is tested and found to be valid.-from Authors
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.
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