Cistecephalus Assemblage Zone
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The ''Cistecephalus'' Assemblage Zone is a
tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...
assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group, a majorly fossiliferous and geologically important geological group of the Karoo Supergroup in
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
. This biozone has outcrops located in the Teekloof Formation north-west of Beaufort West in the
Western Cape The Western Cape ( ; , ) is a provinces of South Africa, province of South Africa, situated on the south-western coast of the country. It is the List of South African provinces by area, fourth largest of the nine provinces with an area of , an ...
, in the upper Middleton and lower Balfour Formations respectively from Colesberg of the
Northern Cape The Northern Cape ( ; ; ) is the largest and most sparsely populated Provinces of South Africa, province of South Africa. It was created in 1994 when the Cape Province was split up. Its capital is Kimberley, South Africa, Kimberley. It includes ...
to east of Graaff-Reinet in the
Eastern Cape The Eastern Cape ( ; ) is one of the nine provinces of South Africa. Its capital is Bhisho, and its largest city is Gqeberha (Port Elizabeth). Due to its climate and nineteenth-century towns, it is a common location for tourists. It is also kno ...
. The ''Cistecephalus'' Assemblage Zone is one of eight biozones found in the Beaufort Group, and is considered to be Late Permian in age. The name of the biozone refers to '' Cistecephalus'', a small, burrowing dicynodont therapsid. It is characterized by the presence of this species, known especially from the upper sections of this biozone, and the first appearance of the dicynodont '' Aulacephalodon''.


History

The first
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s to be found in the Beaufort Group rocks that encompass the current eight biozones were discovered by Andrew Geddes Bain in 1856. 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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
. The initial undertaking was done by Harry Govier Seeley who subdivided the Beaufort Group into three biozones, which he named (from oldest to youngest): * Zone of "
Pareiasaur Pareiasaurs (meaning "cheek lizards") are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with osteoderms which covered large areas of the body. They first appeared in southern Pangea during the Middle Per ...
ians" * Zone of " Dicynodonts" * Zone of "highly specialized group of
theriodont The theriodonts (clade Theriodontia) are a major group of therapsids which appeared during the Middle Permian and which includes the gorgonopsians and the eutheriodonts, itself including the therocephalians and the cynodonts. Naming In 1876, ...
s" These proposed biozones Seeley named were subdivided further by
Robert Broom Robert Broom Fellow of the Royal Society, FRS FRSE (30 November 1866 6 April 1951) was a British- South African medical doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University ...
between 1906 and 1909. Broom proposed the following biozones (from oldest to youngest): * ''
Pareiasaurus ''Pareiasaurus'' (from , "cheek" and , "lizard") is an extinct genus of Pareiasauromorpha, pareiasauromorph reptile from the Permian period. It was a typical member of its family (biology), family, the pareiasaurids, which take their name from th ...
'' beds * '' Endothiodon'' beds * '' Kistecephalus'' beds * '' Lystrosaurus'' beds * '' Procolophon'' beds * '' Cynognathus'' beds These biozone divisions were approved by paleontologists of the time and were left largely unchanged for several decades. The '' Cistecephalus'' Assemblage Zone was first coined by
Robert Broom Robert Broom Fellow of the Royal Society, FRS FRSE (30 November 1866 6 April 1951) was a British- South African medical doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University ...
in 1906, where Broom referred to the rock layers '' Cistecephalus''
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s were found in as the "Kistecephalus beds". The biozone was originally assigned to a far more broader stratigraphic range between the uppermost occurrence of '' Endothiodon'' and the lowermost of '' Lystrosaurus''. Decades later, James Kitching revised the biostratigraphic ranges of the Beaufort Group. Kitching observed that '' Cistecephalus''
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s were most abundant in a narrow band at the very top of the biozone. He named this area the ''" Cistecephalus'' acme zone" or "'' Cistecephalus'' Band". Later, researchers sought to redefine the biozone again as '' Cistecephalus'' fossils are extremely rare apart from the uppermost portion. It was suggested that, due to the biozone containing the first appearance of '' Aulacephalodon'' and its fossils being found throughout, the biozone should be renamed to the ''Aulacephalodon'' Assemblage Zone. The biozone was then, for a brief time, renamed the '' Aulacephalodon- Cistecephalus'' Assemblage Zone. However, due to the biozone first being named after '' Cistecephalus'', the initial nomenclature of the biozone later overruled its renaming on historical grounds.


Lithology

The '' Cistecephalus'' Assemblage Zone is located in the lower portion of the Teekloof Formation west of 24°E, in the upper Middleton Formation and lower Balfour Formation east of 24°E. These formations all fall within the Adelaide Subgroup of the Beaufort Group, sediments of which were formed in a large retroarc
foreland basin A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithospher ...
in southwestern
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
. The sedimentary rocks are mainly
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
, mudrock layers containing mudstone, siltstone, and fine sandstone. The sandstones are thought to have been deposited in broad
alluvial Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...
plains where low- sinuosity streams flowed, while the mudrock accumulated on the
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
s that flanked these streams. The majority of the
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s in the biozone are found in these interchannel mudrock layers as animal remains that came to rest on the floodplains were quickly buried by alluvial sediments washed downstream. Articulated fossils are not commonly found. However, isolated skulls are fairly common and are usually found encased in
calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...
nodules. Fossils not encased in nodules are often fragmented. In addition, Jurassic-aged dolerite sheet and dike
intrusions In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of Intrusive rock, intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety o ...
into the Beaufort Group have affected the uniformity in colour and texture of the biozone rocks in areas. This includes the colour of the fossilized bones, which range from a smooth, white appearance to being nearly black depending on their proximity to the dolerite
intrusions In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of Intrusive rock, intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety o ...
.


Paleontology

The '' Cistecephalus'' biozone is well known for its diversity of
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...
, especially of therapsid species. It is arranged into lower and upper zones due to the appearance or frequency of certain fossils. The lower zones are characterized by the first appearance of the dicynodont species '' Aulacephalodon'' and ''
Oudenodon ''Oudenodon'' is an extinct genus of dicynodont. It was common throughout southern Africa during the Late Permian. Several species of ''Oudenodon'' are known. Both ''O. bainii'', the type species, and ''O. grandis'' are known from South Africa ...
''. Other species found are the
Biarmosuchia Biarmosuchia is an extinct clade of non-mammalian synapsids from the Permian. Biarmosuchians are the most basal group of the therapsids. They were moderately-sized, lightly built carnivores, intermediate in form between basal sphenacodont " pel ...
n therapsid ''
Herpetoskylax ''Herpetoskylax'' is an extinct genus of biarmosuchian therapsids which existed in South Africa. The type species is ''Herpetoskylax hopsoni''.Sidor, C.A., and Rubidge, B.S. (2006). "''Herpetoskylax hopsoni'', a new biarmosuchian (Therapsida: Bia ...
'', Burnetiamorph species namely '' Lemurosaurus'', and numerous Gorgonopsian species such as '' Lycaenops'', '' Rubidgea'', and '' Dinogorgon''. In addition species of Dicynodonts such as '' Endothiodon'' and '' Diictodon'',
Therocephalia Therocephalia is an extinct clade of therapsids (mammals and their close extinct relatives) from the Permian and Triassic periods. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their te ...
ns,
Pareiasaur Pareiasaurs (meaning "cheek lizards") are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with osteoderms which covered large areas of the body. They first appeared in southern Pangea during the Middle Per ...
s, and rare occurrences of parareptiles such as '' Owenetta'' and '' Milleretta'' have been found in the upper zones. The
temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...
amphibian '' Rhinesuchus'', and some fish and plant species have also been found. A dicynodont track way is also known in an outcrop of the biozone east of Graaff-Reinet. '' Cistecephalus'' fossils are rare until the uppermost portion of the biozone where the "'' Cistecephalus'' Band" is located.


Correlations

Correlations in
biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology ...
have been made with the '' Cistecephalus'' zone to geological formations outside of
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
. An '' Endothiodon'' snout was discovered in the Rio do Rasto Formation in
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
, and '' Cistecephalus'' fossils have been found in Madumabisa Mudstone in
Zambia Zambia, officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa. It is typically referred to being in South-Central Africa or Southern Africa. It is bor ...
. Recently, a new cistecephalid dicynodont was discovered in the Kundaram Formation of the Pranhita-Godavari Valley in
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
. The zone also correlates with the Malokinelskaya and Vyazovskaya Formations of Russia.


See also

* List of fossiliferous stratigraphic units in South Africa * Geology of South Africa * Fremouw Formation


References

{{reflist South African assemblage zones Permian South Africa Wuchiapingian