The ''Daptocephalus'' Assemblage Zone is a

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...

assemblage zone or

biozone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties of ...

found in the Adelaide Subgroup of the

Beaufort Group The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup in South Africa. It is composed of a lower Adelaide Subgroup and an upper Tarkastad Subgroup. It follows conformably after the Ecca Group and unconformably underlie ...

, a majorly

fossiliferous 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 preserved in ...

and geologically important geological Group of the

Karoo Supergroup The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a perio ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

.Rubidge, B. S. (1995). Biostratigraphy of the Beaufort Group (Karoo Supergroup). ''Biostratigraphic series''. This biozone has outcrops located in the upper

Teekloof Formation The Teekloof Formation is a geological formation that forms part of the Beaufort Group, one of the five geological groups that comprises the Karoo Supergroup in South Africa. The Teekloof Formation is the uppermost formation of Adelaide Subgroup ...

west of 24°E, the majority of the

Balfour Formation The Balfour Formation is a geological formation that is found in the Beaufort Group, a major geological group that forms part of the greater Karoo Supergroup in South Africa. The Balfour Formation is the uppermost formation of the Adelaide Subgro ...

east of 24°E, and the

Normandien Formation The Normandien Formation is a Triassic-age rock formation located in Free State, South Africa. It is where the fossils of Ericiolacerta, a subtaxa of Ericiolacertidae, were found. Fossil content Among others, these fossils were reported from t ...

in the north. It has numerous localities which are spread out from

Colesberg Colesberg is a town with 17,354 inhabitants in the Northern Cape province of South Africa, located on the main N1 road from Cape Town to Johannesburg. In a sheep-farming area spread over half-a-million hectares, greater Colesberg breeds many ...

in the

Northern Cape The Northern Cape is the largest and most sparsely populated province of South Africa. It was created in 1994 when the Cape Province was split up. Its capital is Kimberley. It includes the Kalahari Gemsbok National Park, part of the Kgalagadi T ...

, Graaff-Reniet to

Mthatha Mthatha , formerly Umtata, is the main city of the King Sabata Dalindyebo Local Municipality in Eastern Cape province of South Africa and the capital of OR Tambo District Municipality. The city has an airport, previously known as the K. D. Matanzi ...

in the

Eastern Cape The Eastern Cape is one of the provinces of South Africa. Its capital is Bhisho, but its two largest cities are East London and Gqeberha. The second largest province in the country (at 168,966 km2) after Northern Cape, it was formed in ...

, and from

Bloemfontein Bloemfontein, ( ; , "fountain of flowers") also known as Bloem, is one of South Africa's three capital cities and the capital of the Free State (province), Free State province. It serves as the country's judicial capital, along with legisla ...

Harrismith Harrismith is a large town in the Free State province of South Africa. It was named for Sir Harry Smith, a 19th-century British governor and high commissioner of the Cape Colony. It is situated by the Wilge River, alongside the N3 highway, abo ...

in the Free State. The ''Daptocephalus'' Assemblage Zone is one of eight biozones found in the

and is considered Late

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

(

Lopingian The Lopingian is the uppermost series/last epoch of the Permian. It is the last epoch of the Paleozoic. The Lopingian was preceded by the Guadalupian and followed by the Early Triassic. The Lopingian is often synonymous with the informal terms l ...

) in age. Its contact with the overlying ''Lystrosaurus'' Assemblage Zone marks the Permian-Triassic boundary. Previously known as the ''Dicynodon'' Assemblage Zone, the name of the biozone refers to ''

Daptocephalus ''Daptocephalus'' is an extinct genus of non- mammalian synapsid anomodont dicynodont, it which was found in Late Permian strata, in a biozone known precisely for the presence of fossils of this dicynodont, the ''Daptocephalus'' Zone, in the Ka ...

'', a medium-sized

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typicall ...

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

. It is characterized by the presence of this species in co-occurrence with ''

Theriognathus microps ''Theriognathus'' (from Greek therion: beast, mammal, Greek, gnathos, “jaw,” +us, pronounced THEH-ree-OG-nah-thuss) is an extinct genus of therocephalian therapsid belonging to the family Whaitsiidae, known from fossils from South Africa, Z ...

'', and ''

Dicynodon lacerticeps ''Dicynodon'' ("two dog-teeth") is a genus of dicynodont therapsid that flourished during the Permian, Upper Permian Period (geology), period. Like all dicynodonts, it was herbivore, herbivorous animal. This reptile was toothless, except for prom ...

.''

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 preserved ...

s to be found in the

rocks that encompass the current eight

s were discovered by

Andrew Geddes Bain Andrew Geddes Bain (baptised 11 June 1797 – 20 October 1864), was a South African geologist, road engineer, palaeontologist and explorer. Life history The only child of Alexander Bain and Jean Geddes, both of whom died when Bain was still a ...

in 1856. However, it was not until 1892 that it was observed that the geological strata of the

could be differentiated based on their

taxa In biology, a taxon (back-formation from ''taxonomy''; plural 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 nam ...

. The initial undertaking was done by

Harry Govier Seeley Harry Govier Seeley (18 February 1839 – 8 January 1909) was a British paleontologist. Early life Seeley was born in London on 18 February 1839, the second son of Richard Hovill Seeley, a goldsmith, and his second wife Mary Govier. When his fat ...

who subdivided the

into three

s, 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 scutes which covered large areas of the body. They first appeared in southern Pangea during the Middle Permian, ...

ians" * Zone of "

Dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typicall ...

s" * 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, Rich ...

s" These proposed biozones Seeley named were subdivided further by

Robert Broom Robert Broom FRS FRSE (30 November 1866 6 April 1951) was a British- South African doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University of Glasgow. From 1903 to 1910, he ...

between 1906 and 1909.

Broom A broom (also known in some forms as a broomstick) is a cleaning tool consisting of usually stiff fibers (often made of materials such as plastic, hair, or corn husks) attached to, and roughly parallel to, a cylindrical handle, the broomstick. I ...

proposed the following

s (from oldest to youngest): * ''

Pareiasaurus ''Pareiasaurus'' is an extinct genus of pareiasauromorph reptile from the Permian period. It was a typical member of its family, the pareiasaurids, which take their name from this genus. Fossils have been found in the Beaufort Group. Descript ...

'' beds * ''

Endothiodon ''Endothiodon'' (/ɛndoʊθiːoʊdɔːn/ "inner tooth" from Greek endothi (ἔνδοθῐ), "within", and odon (ὀδών), "tooth", most likely named for the characteristic of the teeth being placed internally to the maxillaBoos A. S., Schultz C ...

'' beds * '' Kistecephalus'' beds * ''

Lystrosaurus ''Lystrosaurus'' (; 'shovel lizard'; proper Greek is λίστρον ''lístron'' ‘tool for leveling or smoothing, shovel, spade, hoe’) is an extinct genus of herbivorous dicynodont therapsids from the late Permian and Early Triassic epochs (a ...

'' beds * ''

Procolophon ''Procolophon'' is a genus of lizard-like procolophonid parareptiles that first appeared in the Early Triassic (Induan) of South Africa, Brazil, and Antarctica. It persisted through the Permian–Triassic extinction event, but went extinct in th ...

'' beds * ''

Cynognathus ''Cynognathus'' is an extinct genus of large-bodied cynodontian therapsids that lived in the Middle Triassic. It is known from a single species, ''Cynognathus crateronotus''. ''Cynognathus'' was a long predator closely related to mammals and ha ...

'' beds These

divisions were approved by paleontologists of the time and were left largely unchanged for several decades. The ''Daptocephalus'' Assemblage Zone was first named after the

'' Daptocephlaus leoniceps'' by

James Kitching James William Kitching (6 February 1922 – 24 December 2003) was a South African vertebrate palaeontologist and regarded as one of the world’s greatest fossil finders. Career His work in the southern hemisphere, including Antarctica, led ...

due to the high prevalence, and localized appearance, of this species. However, the name of the biozone was changed to the ''Dicynodon'' Assemblage Zone as it was argued that ''

'' was in fact a juvenile of ''

Dicynodon ''Dicynodon'' ("two dog-teeth") is a genus of dicynodont therapsid that flourished during the Upper Permian period. Like all dicynodonts, it was herbivorous animal. This reptile was toothless, except for prominent tusks, hence the name. It probab ...

''. In addition it was thought that ''

'' was a more suitable taxon for global biostratigraphic correlation of other Karoo-aged basins, namely to those 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, although it is typically referred to as being in Southern Africa at its most cent ...

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

, and

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

. In recent years, with new paleontological finds and updated logging of geological formations and biostratigraphy of the

Karoo Basin The Karoo Supergroup is the most widespread stratigraphy, stratigraphic unit in Africa south of the Kalahari Desert. The group (stratigraphy), supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Pennsylvan ...

, it was found that there has been some taxonomic confusion with ''

'' fossils. In addition, recent taxonomic studies have shown that ''

'' is indeed its own species, and is only found within the confines of the biozone. Subsequently it was renamed the ''Daptocephalus'' Assemblage Zone.

Lithology

The ''Daptocephalus'' Assemblage Zone is located only in the upper Balfour formation and lower Normandien formation east of 24°E. These formations all fall within the Adelaide Subgroup of the

, 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 south-western

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

. The biozone is subdivided into the lower ''

Theriognathus ''Theriognathus'' (from Greek therion: beast, mammal, Greek, gnathos, “jaw,” +us, pronounced THEH-ree-OG-nah-thuss) is an extinct genus of therocephalian therapsid belonging to the family Whaitsiidae, known from fossils from South Africa, Z ...

'' subzone and the upper ''

Moschorhinus ''Moschorhinus'' is an extinct genus of therocephalian in the family Akidnognathidae with only one species: ''M. kitchingi''. It was a carnivorous synapsid which has been found in the Late Permian to Early Triassic of the South African Karoo Supe ...

'' subzone. This satisfies the appearance of '' Lystrosaurus maccaigi'' below the ''Lystrosaurus'' Assemblage Zone boundary, and the disappearance of the lower subzone taxa ''

'', ''

'', and '' Procynosuchus delaharpeae''. At the time of sedimentary deposition, the

Karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe !Orakobab or Khoemana word ''ǃ’Aukarob'' "Hardveld") is a semi-desert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its ext ...

retroarc foreland system was in an overfilled phase, and purely terrestrial sediments occupied the

at this time. Two fining-upward sequences are observed in the sedimentary

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

of ''

'' biozone, bounded by a second-order subaerial

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

. These

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s comprise greenish-grey

mudrock Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too ...

with

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

lenses A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

in the lower to middle sections of the

, which are indicative of a low-energy fluvial environments with meandering rivers. It is in these rocks that

s are most commonly found. As the biozone reaches its termination, its contact with the overlying Katberg Formation marks a sharp change in the lithology. The sedimentary rocks change to being sandstone-rich with these sandstone bodies commonly appearing within outcrops of brownish-red

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

and reddish

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

. The appearance and proliferation of these sandstone deposits marks the change to braided river systems where sands were only deposited with the finer sediments being washed further downstream. Fossil abundance and preservation quality does not change across the boundary, however, species abundance does due to the extinction event, and also the preservational style of the fossils. More isolated skulls are found in the Permian, whereas in the earliest Triassic, curled up complete skeletons are more common as are bonebeds. These lithological and taphonomic changes are used as evidence for the sudden drying of the climate associated with the Permian-Triassic extinction event.

Paleontology

The lower to middle zones of the ''Daptocephlaus'' Assemblage Zone display a great diversity of vertebrate fauna. These include its current type species ''

'' and other

s such as the ubiquitous ''

Diictodon ''Diictodon'' is an extinct genus of pylaecephalid dicynodont. These mammal-like synapsids lived during the Late Permian period, approximately 255 million years ago. Fossils have been found in the ''Cistecephalus'' Assemblage Zone of the Mad ...

'', ''

Dinanomodon ''Dinanomodon'' is a genus of dicynodont from Late Permian (Changhsingian) of the ''Lystrosaurus'' Assemblage Zone, Katberg Formation, and ''Cistecephalus'' Assemblage Zone, Balfour Formation Beaufort Group, Karoo Basin of South Africa ...

'', and ''

Pristerodon ''Pristerodon'' is an extinct genus of dicynodont therapsid from the Late Permian of South Africa, Zambia and India. Paleobiology Brain and senses ''Pristerodon'' were among the earliest land animals able to hear airborne sound as opposed to ...

''. Various species of burnetiamorph

Biarmosuchia Biarmosuchians are an extinct clade of non-mammalian synapsids from the Permian. They are the most basal group of the therapsids. All of them were moderately-sized, lightly-built carnivores, intermediate in form between basal sphenacodont "pelyc ...

ns and Rubidgenae

Gorgonopsia Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skull, a ...

ns are also found.

Therocephalia Therocephalia is an extinct suborder of eutheriodont therapsids (mammals and their close relatives) from the Permian and Triassic. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their te ...

n species such as '' Moschorhinus kitchingi'' and the earliest

cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...

'' Charassognathus gracilis'' also appear.

Parareptile Parareptilia ("at the side of reptiles") is a subclass or clade of basal sauropsids (reptiles), typically considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds). Parareptiles first arose near the ...

species, namely

captorhinids Captorhinidae (also known as cotylosaurs) is an extinct family of tetrapods, traditionally considered primitive reptiles, known from the late Carboniferous to the Late Permian. They had a cosmopolitan distribution across Pangea. Description C ...

, the Younginiforme ''

Youngina ''Youngina'' is an extinct genus of diapsid reptile from the Late Permian Beaufort Group (''Tropidostoma''-''Dicynodon'' zones) of the Karoo Red Beds of South Africa. This, and a few related forms, make up the family Younginidae, within the Orde ...

'', and a variety of

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order (biology), order of small to giant tetrapods—often considered Labyrinthodontia, primitive amphi ...

amphibians, fishes, and plant fossils such as ''

Glossopteris ''Glossopteris'' tymology: from Ancient Greek γλῶσσα (glôssa, " tongue ") + πτερίς (pterís, " fern ")is the largest and best-known genus of the extinct Permian order of seed ferns known as Glossopteridales (also known as Arberia ...

'' are likewise found. The upper zones as the Permian-Triassic boundary approaches, there is a marked drop in species diversity as the Permian-Triassic extinction event began to take its course.

Age and correlations

The ''Daptocephalus'' Assemblage Zone dates to approximately 254.5 to 251 Ma, and correlates with the Kutuluksaya and Kulchomovskaya Formations of Russia, and with the lower

Buena Vista Formation The Buena Vista Formation is a Late Permian/Early Triassic geologic formation of the Cerro Largo Department in northeastern Uruguay. The fluvial sandstones and mudstones preserve temnospondyl and archosaur fossils. Description The Buena Vi ...

of the

Paraná Basin The Paraná Basin ( pt, Bacia do Paraná, es, Cuenca del Paraná) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande d ...

, South America.Ezcurra, 2016, p.8

References

Bibliography

* {{cite journal , last=Ezcurra , first=Martín D , year=2016 , title=The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms , url=https://peerj.com/articles/1778.pdf , journal=

PeerJ ''PeerJ'' is an open access peer-reviewed scientific mega journal covering research in the biological and medical sciences. It is published by a company of the same name that was co-founded by CEO Jason Hoyt (formerly at Mendeley) and publisher Pet ...

, volume=4e1778 , doi=10.7717/peerj.1778 , doi-access=free , access-date=2019-03-14 South African assemblage zones Permian South Africa Changhsingian

History

Lithology

Paleontology

Age and correlations

See also

References

Bibliography