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Tapinocephalus Assemblage Zone

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Tapinocephalus Assemblage Zone
Stratigraphic range: Middle Permian to Late Permian[1]
Tapinocephalus atherstonei
TypeBiozone
Unit ofAbrahamskraal Formation of the Beaufort Group
UnderliesPristerognathus Assemblage Zone
OverliesEodicynodon Assemblage Zone
Thicknessup to 6,561.68 feet (2,000 m)
Location
RegionNorthern, Western & Eastern Cape
Country South Africa
ExtentKaroo Basin
Type section
Named forTapinocephalus atherstonei
Named byWatson (1914), Keyser & Smith (1977-78), Kitching (1984)

The Tapinocephalus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the middle Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. The thickest outcrops, reaching approximately 2,000 metres (6,600 ft), occur from Merweville and Leeu-Gamka in its southernmost exposures, from Sutherland through to Beaufort West where outcrops start to only be found in the south-east, north of Oudshoorn and Willowmore, reaching up to areas south of Graaff-Reinet. Its northernmost exposures occur around the towns Fraserburg and Victoria West. The Tapinocephalus Assemblage Zone is the second biozone of the Beaufort Group.[2][3][4]

The name of the biozone refers to Tapinocephalus atherstonei, a large herbivorous tapinocephalid dinocephalian therapsid. It is characterised by the presence of this dinocephalian species along with the appearance of other advanced tapinocephalid dinocephalians, and the large pareiasaur Bradysaurus baini. It is also the first biozone of the series where the dicynodont, Diictodon feliceps, species first appear.

History

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The first fossils to be found in the Beaufort Group rocks that encompass the current eight biozones were discovered by Andrew Geddes Bain in 1856.[5] However, it was not until 1892 that it was observed that the geological strata of the Beaufort Group could be differentiated based on their fossil taxa. The initial undertaking was done by Harry Govier Seeley who subdivided the Beaufort Group into three biozones,[6] which he named (from oldest to youngest):

These proposed biozones Seeley named were subdivided further by Robert Broom between 1906 and 1909.[7] Broom proposed the following biozones (from oldest to youngest):

The rocks of the current Tapinocephalus Assemblage Zone were first included with those of the lower Eodicynodon Assemblage Zone under the name "Pareiasaurus beds" by Broom.[8][9] Years later Lieuwe Dirk Boonstra redefined the boundaries of the Tapinocephalus Assemblage Zone. As a young man Boonstra collaborated with Broom on research of dinocephalians.[10] After embarking on further study of dinocephalian fossils and their biostratigraphy, Boonstra defined the lower, middle, and upper sections of this biozone.[11][12][13][14] In the 1970s, Keyser and Smith proposed the renaming of the biozone to Dinocephalian Assemblage Zone. In 1984 James Kitching proposed to name the biozone after Tapinocephalus, which was accepted over Keyser and Smith’s proposal. However, the zoning of the biozone rocks remains as they were defined by Keyser and Smith.[15][16]

Lithology

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The Tapinocephalus Assemblage Zone correlates with the Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group. Outcrops of this biozone are known from the south-western and central margins of the Abrahamskraal Formation where it conformably overlies the Eodicynodon Assemblage Zone in its south-western localities. In its northern and eastern localities it inter-fingers with Ecca Group-aged deposits. This biozone is considered to be Middle Permian (Guadalupian) in age.[17]

The rocks of the Tapinocephalus Assemblage Zone consist mainly of maroon to greyish red or purple mudstone layers which exhibit blocky weathering at exposed outcrops. The mudstones contain calcareous nodules and sheet limestones, both are indicative of a warm and seasonally arid climate, revealing the presence of paleocalcretes and carbonate precipitation respectively in playa lakes. Paleosols are also commonly found in the mudstones, which indicates a lack of deposition for long periods of time. In some deposits the mudstone layers contain thin chert lenses which have been attributed to silicified tuff deposits. Alternating beds of light grey to dark greenish grey siltstone and greenish grey to light olive grey sandstones which weather to light orange grey. The siltstones frequently contain both symmetrical and asymmetrical ripple surfaces which indicate that paleocurrents traveled downstream in a northerly direction. Desiccation cracks which are infilled by fine sandstone are also found. The sandstones are fine-grained and mainly tabular, indicating that deposition of these sandstones was in a low-energy fluvial environment. The sandstones are capped in the upper sections of the biozone with mudstone clast conglomerates.[18][19]

The depositional environment of the Tapinocephalus Assemblage Zone was formed by sedimentary material being deposited in the Karoo Basin (a retro-arc foreland basin) by vast, low-energy alluvial plains flowing northwards from a southerly source area in the rising Gondwanide mountains. The Gondwanides were the result of crustal uplift that had previously begun to take course due to subduction of the Palaeo-pacific plate beneath the Gondwanan Plate. Orogenic pulses from the growing Gondwanides mountain chain and associated subduction created accommodation space for sedimentation in the Karoo Basin where the deposits of the Tapinocephalus Assemblage zone, and all other succeeding assemblage zone deposits, were deposited over millions of years.[20][21]

Paleontology

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Bradysaurus baini

The Tapinocephalus Assemblage Zone is characterized by the presence of Tapinocephalus atherstonei and Bradysaurus baini. Vertebrate fossils found in this biozone are not especially common, however are most commonly discovered as articulated single specimens within or associated with the calcareous nodules in the mudstone layers.[22] As the name for this biozone suggests, it is renowned by paleontologists for its diverse Dinocephalian fossil species where almost all members of this family – the Anteosauridae, Titanosuchidae, and Tapinocephalidae – are represented.[23] Example species from these families are Anteosaurus magnificus, Jonkeria boonstrai, and Tapinocephalus atherstonei respectively. Other notable dinocephalian species which have been discovered from this biozone are the advanced tapinocephalids Struthiocephalus whaitsi and Moschops capensis, and the unusual Styracocephalus platyrhynchus.[24][25] Unfortunately dinocephalian fossils are frequently found disarticulated with much of their postcrania missing.[26]

Despite the rarity of fossils, the fossil taxa that have been found from the Tapinocephalus Assemblage Zone are extremely diverse. Parareptile species such as the pareiasaur, Bradysaurus, and the perplexing putative pantestudine Eunotosaurus africanus are confined to this biozone.[27] One of the few pelycosaur species found in South African deposits, Elliotsmithia longiceps,[28] and the biarmosuchian Hipposaurus boonstrai are likewise found, including a variety of basal gorgonopsid,[29][30] anomodont,[31][32] and therocephalian species.[33] The dicynodont Diictodon feliceps first appeared in this biozone and remained ubiquitous until the Permian-Triassic boundary.[34] Other dicynodont species found include Robertia broomiana and Pristerodon brachyops. Finally, fossils of temnospondyl amphibians such as Rhinesuchoides tenuiceps,[35] remains of the fish Namaichthys digitata, invertebrate fossils of molluscs, invertebrate trackways and burrows, vertebrate footprints of therapsids, and a variety of plant fossils, namely of Glossopteris, Dadoxylon, and Schizoneura, have been recovered.

Correlation

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Many dinocephalian species that are found in the Tapinochephalus Assemblage Zone have been found in formations in different countries which correlate in age. As dinocephalian fossils are only known from Middle Permian (Guadalupian) deposits, dinocephalians are good biostratigraphic markers for this period. Dinocephalian fossils, along with other therapsid species found in the Tapinocephalus Assemblage Zone, have been recovered from the Rio do Rasto Formation from the Paraná Basin in Brazil[36] and from the Madumabisa Mudstone in Zambia.[37][38]

See also

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References

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  1. ^ Rubidge, B.S.; Kitching, J.W. (2003). "A new burnetiamorph (Therapsida: Biarmosuchia) from the Lower Beaufort Group of South Africa". Palaeontology. 46 (1): 199–210. doi:10.1111/1475-4983.00294.
  2. ^ Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy. Biostratigraphic Series 1. Pretoria, Council for Geoscience.
  3. ^ van der Walt, Merrill; Day, Michael; Rubidge, Bruce; Cooper, Antony; Netterberg, Inge (2010-12-31). "A new GIS-based biozone map of the Beaufort Group (Karoo Supergroup), South Africa". Palaeontologia Africana. 45: 1–6.
  4. ^ Jirah, Sifelani; Rubidge, Bruce S. (2014-12-01). "Refined stratigraphy of the Middle Permian Abrahamskraal Formation (Beaufort Group) in the southern Karoo Basin". Journal of African Earth Sciences. 100: 121–135. doi:10.1016/j.jafrearsci.2014.06.014. ISSN 1464-343X.
  5. ^ Bain, Andrew Geddes (1845-02-01). "On the Discovery of the Fossil Remains of Bidental and other Reptiles in South Africa". Quarterly Journal of the Geological Society. 1 (1): 317–318. doi:10.1144/GSL.JGS.1845.001.01.72. ISSN 0370-291X. S2CID 128602890.
  6. ^ Seeley, H. G. (1895). "Researches on the Structure, Organization, and Classification of the Fossil Reptilia. Part IX., Section 4. On the Gomphodontia". Philosophical Transactions of the Royal Society of London B. 186: 1–57. doi:10.1098/rstb.1895.0001. JSTOR 91793.
  7. ^ Broom, R. (January 1906). "V.—On the Permian and Triassic Faunas of South Africa". Geological Magazine. 3 (1): 29–30. doi:10.1017/S001675680012271X. ISSN 1469-5081. S2CID 129265956.
  8. ^ Broom, R., 1906. V.—On the Permian and Triassic Faunas of South Africa. Geological Magazine, 3(1), pp.29-30.
  9. ^ Broom, R., 1912, December. On some new fossil reptiles from the Permian and Triassic beds of South Africa. In Proceedings of the Zoological Society of London (Vol. 82, No. 4, pp. 859-876). Oxford, UK: Blackwell Publishing Ltd.
  10. ^ Boonstra, L.D. and Broom, R., 1936. Some features of the cranial morphology of the tapinocephalid deinocephalians. Bulletin of the AMNH; v. 72, article 2.
  11. ^ Boonstra, Lieuwe D. (1938-03-01). "A Report on some Karroo Reptiles from the Luangwa Valley, Northern Rhodesia". Quarterly Journal of the Geological Society. 94 (1–4): 371–384. doi:10.1144/GSL.JGS.1938.094.01-04.14. ISSN 0370-291X. S2CID 129931146.
  12. ^ Boonstra, L.D. (1963-05-01). "Early dichotomies in the Therapsids". South African Journal of Science. 59 (5). ISSN 0038-2353.
  13. ^ Boonstra, L.D., 1968. The braincase, basicranial axis and median septum in the Dinocephalia.
  14. ^ Boonstra, L.D., 1969. The fauna of the Tapinocephalus Zone (Beaufort beds of the Karoo).
  15. ^ Keyser, A.W. and Smith, R.M.H., 1978. Vertebrate biozonation of the Beaufort Group with special reference to the western Karoo Basin. Geological Survey, Department of Mineral And Energy Affairs, Republic of South Africa.
  16. ^ Keyser, A.W., 1979. A review of the biostratigraphy of the Beaufort Group in the Karoo Basin of South Africa. Geocongress, Geological Society of South Africa, 2, pp.13-31.
  17. ^ Day, Michael Oliver; Rubidge, Bruce Sidney (2014-12-01). "A brief lithostratigraphic review of the Abrahamskraal and Koonap formations of the Beaufort Group, South Africa: Towards a basin-wide stratigraphic scheme for the Middle Permian Karoo". Journal of African Earth Sciences. 100: 227–242. doi:10.1016/j.jafrearsci.2014.07.001. ISSN 1464-343X.
  18. ^ Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy. Biostratigraphic Series 1. Pretoria, Council for Geoscience.
  19. ^ Oliver, Day, Michael (2014-03-04). Middle Permian continental biodiversity changes as reflected in the Beaufort Group of South Africa: a bio- and lithostratigraphic review of the Eodicynodon, Tapinocephalus and Pristerognathus assemblage zones (Thesis).{{cite thesis}}: CS1 maint: multiple names: authors list (link)
  20. ^ Hancox, P.J; Rubidge, B.S (2001-01-01). "Breakthroughs in the biodiversity, biogeography, biostratigraphy, and basin analysis of the Beaufort group". Journal of African Earth Sciences. 33 (3–4): 563–577. doi:10.1016/S0899-5362(01)00081-1. ISSN 1464-343X.
  21. ^ Rubidge, Bruce S.; Day, Michael O.; Barbolini, Natasha; Hancox, P. John; Choiniere, Jonah N.; Bamford, Marion K.; Viglietti, Pia A.; McPhee, Blair W.; Jirah, Sifelani (2016), "Advances in Nonmarine Karoo Biostratigraphy: Significance for Understanding Basin Development", Origin and Evolution of the Cape Mountains and Karoo Basin, Springer International Publishing, pp. 141–149, doi:10.1007/978-3-319-40859-0_14, ISBN 9783319408583
  22. ^ Canoville, A. and Chinsamy, A., 2017. Bone Microstructure of Pareiasaurs (Parareptilia) from the Karoo Basin, South Africa: Implications for Growth Strategies and Lifestyle Habits. The Anatomical Record, 300(6), pp.1039-1066.
  23. ^ Atayman, S., Rubidge, B.S. and Abdala, F., 2009. Taxonomic re-evaluation of tapinocephalid dinocephalians. Palaeontologia africana, 44, p.88Á90. Link: https://core.ac.uk/download/pdf/39675877.pdf#page=88
  24. ^ Rubidge, Bruce; VAN DEN HEEVER, J.A (1997-01-01). "Morphology and systematic position of the dinocephalian Styracocephalus platyrhynchus (Amniota: Therapsida)". Lethaia. 30: 157–168. doi:10.1111/j.1502-3931.1997.tb00457.x.
  25. ^ Rubidge, Bruce S.; Sidor, Christian A. (2002-07-08). "On the cranial morphology of the basal therapsids Burnetia and Proburnetia (Therapsida: Burnetiidae)". Journal of Vertebrate Paleontology. 22 (2): 257–267. doi:10.1671/0272-4634(2002)022[0257:otcmot]2.0.co;2. ISSN 0272-4634. S2CID 86207308.
  26. ^ Day, Michael O.; Güven, Saniye; Abdala, Fernando; Jirah, Sifelani; Rubidge, Bruce; Almond, John (April 2015). "Youngest dinocephalian fossils extend the Tapinocephalus Zone, Karoo Basin, South Africa". South African Journal of Science. 111 (3–4): 1–5. doi:10.17159/sajs.2015/20140309. ISSN 0038-2353.
  27. ^ Lyson, Tyler R.; Bever, Gabe S.; Scheyer, Torsten M.; Hsiang, Allison Y.; Gauthier, Jacques A. (2013-06-17). "Evolutionary Origin of the Turtle Shell". Current Biology. 23 (12): 1113–1119. doi:10.1016/j.cub.2013.05.003. ISSN 0960-9822. PMID 23727095.
  28. ^ Reisz, Robert R.; Dilkes, David W.; Berman, David S (1998-09-15). "Anatomy and relationships ofElliotsmithia longicepsBroom, a small synapsid (Eupelycosauria: Varanopseidae) from the late Permian of South Africa". Journal of Vertebrate Paleontology. 18 (3): 602–611. doi:10.1080/02724634.1998.10011087. ISSN 0272-4634.
  29. ^ Kammerer, Christian F. (2013-09-21), "A Redescription of Eriphostoma microdon Broom, 1911 (Therapsida, Gorgonopsia) from the Tapinocephalus Assemblage Zone of South Africa and a Review of Middle Permian Gorgonopsians", Early Evolutionary History of the Synapsida, Vertebrate Paleobiology and Paleoanthropology, Springer Netherlands, pp. 171–184, doi:10.1007/978-94-007-6841-3_11, ISBN 9789400768406
  30. ^ Kammerer, C.F., Smith, R.M., Day, M.O. and Rubidge, B.S., 2015. New information on the morphology and stratigraphic range of the mid‐Permian gorgonopsian E riphostoma microdon Broom, 1911. Papers in Palaeontology, 1(2), pp.201-221.
  31. ^ Cisneros, Juan Carlos; Abdala, Fernando; Jashashvili, Tea; de Oliveira Bueno, Ana; Dentzien-Dias, Paula (July 2015). "Tiarajudens eccentricus and Anomocephalus africanus, two bizarre anomodonts (Synapsida, Therapsida) with dental occlusion from the Permian of Gondwana". Royal Society Open Science. 2 (7): 150090. doi:10.1098/rsos.150090. ISSN 2054-5703. PMC 4632579. PMID 26587266.
  32. ^ Angielczyk, Kenneth D.; Rubidge, Bruce S.; Day, Michael O.; Lin, Florence (2016-02-06). "A reevaluation ofBrachyprosopus broomiandChelydontops altidentalis, dicynodonts (Therapsida, Anomodontia) from the middle PermianTapinocephalusAssemblage Zone of the Karoo Basin, South Africa". Journal of Vertebrate Paleontology. 36 (2): e1078342. doi:10.1080/02724634.2016.1078342. ISSN 0272-4634. S2CID 130520407.
  33. ^ Boonstra, L.D., 1965. The girdles and limbs of the Gorgonopsia of the Tapinocephalus Zone. Annals of the South African Museum, 48(13), pp.237-249.
  34. ^ ANGIELCZYK, KENNETH D.; RUBIDGE, BRUCE S. (September 2010). "A new pylaecephalid dicynodont (Therapsida, Anomodontia) from the Tapinocephalus Assemblage Zone, Karoo Basin, Middle Permian of South Africa". Journal of Vertebrate Paleontology. 30 (5): 1396–1409. doi:10.1080/02724634.2010.501447. ISSN 0272-4634. S2CID 129846697.
  35. ^ Damiani, Ross J. (2004-01-01). "Temnospondyls from the Beaufort Group (Karoo Basin) of South Africa and Their Biostratigraphy". Gondwana Research. 7 (1): 165–173. doi:10.1016/S1342-937X(05)70315-4. ISSN 1342-937X.
  36. ^ Boos, A.D.S.; Kammerer, C.F.; Schultz, C.L.; Paes Neto, V.D. (2015-11-01). "A tapinocephalid dinocephalian (Synapsida, Therapsida) from the Rio do Rasto Formation (Paraná Basin, Brazil): Taxonomic, ontogenetic and biostratigraphic considerations". Journal of South American Earth Sciences. 63: 375–384. doi:10.1016/j.jsames.2015.09.003. ISSN 0895-9811.
  37. ^ Sidor, Christian A.; Angielczyk, Kenneth D.; Smith, Roger M. H.; Goulding, Adam K.; Nesbitt, Sterling J.; Peecook, Brandon R.; Steyer, J. Sébastien; Tolan, Stephen (2014-06-07). "Tapinocephalids (Therapsida, Dinocephalia) from the Permian Madumabisa Mudstone Formation (Lower Karoo, Mid-Zambezi Basin) of southern Zambia". Journal of Vertebrate Paleontology. 34 (4): 980–986. doi:10.1080/02724634.2013.826669. ISSN 0272-4634. S2CID 128431441.
  38. ^ Sidor, Christian (2015-04-09). "The first biarmosuchian from the upper Madumabisa Mudstone Formation (Luangwa Basin) of Zambia". Palaeontologia Africana. 49: 1–7.
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