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30-482: 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. The first fossils to be found in

60-403: A type section designated as a stratotype . These stratotypes are named according to the typical taxon (or taxa) that are found in that particular biozone. The boundary of two distinct biostratigraphic units is called a biohorizon . Biozones can be further subdivided into subbiozones , and multiple biozones can be grouped together in a superbiozone in which the grouped biozones usually have

90-416: A minor unit in a formation of rock, similar to a member but not generally spread out over a large geographical area. In this usage, the lentil thins out towards its edges. Lenticular bedding is a special form of rock interbedded mudrock and cross-laminated rippled sandstone . The lenses or ripples in lenticular beds are discontinuous in all directions. This article related to petrology

120-495: 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 . The depositional environment of the Tapinocephalus Assemblage Zone

150-494: A related characteristic. A succession of biozones is called biozonation . The length of time represented by a biostratigraphic zone is called a biochron . The concept of a biozone was first established by the 19th century paleontologist Albert Oppel , who characterized rock strata by the species of the fossilized animals found in them, which he called zone fossils. Oppel's biozonation was mainly based on Jurassic ammonites he found throughout Europe, which he used to classify

180-458: A small portion of fossils are preserved, a biozone does not represent the true range of that species in time. Moreover, ranges can be influenced by the Signor-Lipps effect , meaning that the last "disappearance" of a species tends to be observed further back in time than was actually the case. Lens (geology) In geology , a lens or lentil is a body of ore or rock that is thick in

210-415: A taxon (or taxa). There are two types of range zones: A taxon-range zone is simply the biozone defined by the first ( first appearance datum or FAD ) and last ( last appearance datum or LAD ) occurrence of a single taxon. The boundaries are defined by the lowest and highest stratigraphic occurrence of that particular taxon. Taxon-range zones are named after the taxon in it. A concurrent-range zone uses

240-449: A taxon and the lowest occurrence of its descendant. Lineage zones are different from most other biozones because they need that the segments its bounded by are successive segments of an evolutionary lineage. This makes them similar to chronostratigraphical units - however, lineage zones, being a biozone, are restricted by the actual spatial range of fossils. Lineage zones are named for the specific taxon they represent. An assemblage zone

270-404: Is a biozone defined by three or more different taxa, which may or may not be related. The boundaries of an assemblage zone are defined by the typical, specified fossil assemblage's occurrence: this can include the appearance, but also the disappearance of certain taxa. Assemblage zones are named for the most characteristic or diagnostic fossils in its assemblage. An abundance zone, or acme zone ,

300-409: Is a biozone that is defined by the range in which the abundance of a particular taxon is highest. Because an abundance zone requires a statistically high proportion of a particular taxon, the only way to define them is to trace the abundance of the taxon through time. As local environmental factors influence abundance, this can be an unreliable way of defining a biozone. Abundance zones are named after

330-445: Is defined by the zone fossils it contains. These may be a single taxon or combinations of taxa if the taxa are relatively abundant, or variations in features related to the distribution of fossils. The same strata may be zoned differently depending on the diagnostic criteria or fossil group chosen, so there may be several, sometimes overlapping, biostratigraphic units in the same interval. Like lithostratigraphic units, biozones must have

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360-478: 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

390-718: 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. The rocks of

420-560: 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 taxa . The initial undertaking was done by Harry Govier Seeley who subdivided the Beaufort Group into three biozones , which he named (from oldest to youngest): These proposed biozones Seeley named were subdivided further by Robert Broom between 1906 and 1909. Broom proposed

450-592: The Permian-Triassic boundary . Other dicynodont species found include Robertia broomiana and Pristerodon brachyops . Finally, fossils of temnospondyl amphibians such as Rhinesuchoides tenuiceps , 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. Many dinocephalian species that are found in

480-700: The Rio do Rasto Formation from the Paraná Basin in Brazil and from the Madumabisa Mudstone in Zambia . 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 the surrounding rock. A biostratigraphic unit

510-432: 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

540-578: The calcareous nodules in the mudstone layers. 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. 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

570-507: 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

600-548: The pareiasaur , Bradysaurus , and the perplexing putative pantestudine Eunotosaurus africanus are confined to this biozone. One of the few pelycosaur species found in South African deposits, Elliotsmithia longiceps , and the biarmosuchian Hipposaurus boonstrai are likewise found, including a variety of basal gorgonopsid , anomodont , and therocephalian species. The dicynodont Diictodon feliceps first appeared in this biozone and remained ubiquitous until

630-419: The advanced tapinocephalids Struthiocephalus whaitsi and Moschops capensis , and the unusual Styracocephalus platyrhynchus . Unfortunately dinocephalian fossils are frequently found disarticulated with much of their postcrania missing. Despite the rarity of fossils, the fossil taxa that have been found from the Tapinocephalus Assemblage Zone are extremely diverse. Parareptile species such as

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660-415: The appearance of one taxon, and the lower boundary the appearance of another taxon. A lineage zone, also called a consecutive range zone , are biozones which are defined by being a specific segment of an evolutionary lineage. For example, a zone can be bounded by the highest occurrence of the ancestor of a particular of a taxon and the lowest occurrence of its descendant, or between the lowest occurrence of

690-524: 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 . 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 . After embarking on further study of dinocephalian fossils and their biostratigraphy, Boonstra defined

720-704: 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. 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

750-443: The lower, middle, and upper sections of this biozone. 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. The Tapinocephalus Assemblage Zone correlates with

780-404: The middle and thin at the edges, resembling a convex lens in cross-section. To thin out in all directions is to "lens out", also known as "lensing". The adjectives "lenticular" and "lentiform" are used to describe lens-like formations. Lenticle is a synonym for lentil, but may also refer to a fragment of rock that is lens-shaped. "Lenticule" is used for small lentil. A lentil may also refer

810-413: The overlapping range of two taxa, with low boundary defined by the appearance of one taxon and high boundary defined by the disappearance of the other taxon. Concurrent-range zones are named after both of the taxa in it. An interval zone is defined as the body of strata between two bio-horizons, which are arbitrarily chosen. For example, a highest-occurrence zone is a biozone with the upper boundary being

840-419: The period into 33 zones (now 60). Alcide d'Orbigny would further reinforce the concept in his Prodrome de Paléontologie Stratigraphique , in which he established comparisons between geological stages and their biostratigraphy. The International Commission on Stratigraphy defines the following types of biozones: Range zones are biozones defined by the geographic and stratigraphic range of occurrence of

870-586: The taxon that is the most abundant within its range. A great variety of species can be used in establishing biozonation. Graptolites and ammonites are some of the most useful as zone fossils, as they preserve well and often have relatively short biozones. Microfossils , such as dinoflagellates , foraminiferans , or plant pollen are also good candidates because they tend to be present even in very small samples and evolve relatively rapidly. Fossils of pigs and cannabis can be used for biozonation of Quaternary rocks as they were used by hominids . As only

900-594: 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

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