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
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
calcareousnodules 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
chertlenses which have been attributed to
silicifiedtuff 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
mudstoneclastconglomerates.[18][19]
The depositional environment of the Tapinocephalus Assemblage Zone was formed by
sedimentary material being deposited in the
Karoo Basin (a
retro-arcforeland 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]
^Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy. Biostratigraphic Series 1. Pretoria, Council for Geoscience.
^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.
ISSN1464-343X.
^Broom, R., 1906. V.—On the Permian and Triassic Faunas of South Africa. Geological Magazine, 3(1), pp.29-30.
^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.
^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.
^Boonstra, L.D., 1968. The braincase, basicranial axis and median septum in the Dinocephalia.
^Boonstra, L.D., 1969. The fauna of the Tapinocephalus Zone (Beaufort beds of the Karoo).
^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.
^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.
^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:
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^Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy. Biostratigraphic Series 1. Pretoria, Council for Geoscience.
^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.
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^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,
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^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.
^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.
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^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,
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^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.
^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.
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^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.
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^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.
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