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Calodiscidae
The Calodiscidae Kobayashi, 1943 'nom. transl.'' Öpik, 1975 ''ex'' Calodiscinae Kobayashi, 1943are a family of trilobites belonging to the order Agnostida that lived during the Lower Cambrian (Botomian and Toyonian). They are small or very small, and have a thorax of two or three segments. The Calodiscidae includes five genera (see box). Taxonomy The probable ancestors of the Calodiscidae are among the Tsunydiscidae. The Calodiscidae had no descendants. cited ''in'' Description Like all Agnostida, the Calodiscidae are diminutive and the headshield (or cephalon) and tailshield (or pygidium) are of approximately the same size (or isopygous) and outline. The central raised area of the cephalon (or glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...) has parallel sid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eodiscina
Eodiscina is trilobite suborder. The Eodiscina first developed near the end of the Lower Cambrian period (late Atdabanian) and became extinct at the end of the Middle Cambrian. Species are tiny to small, and have a thorax of two or three segments. Eodiscina includes six families classified under one superfamily, Eodiscoidea. Taxonomy The Eodiscina are mostly considered the more primitive suborder of the Agnostida, and the Agnostina the more advanced. Some scholars do not consider the Agnostina true trilobites, and consequently rejected the idea that they were related to the Eodiscina. Consequently, these scientists have proposed to elevate the group to ordinal level, which would thus be called Eodiscida Kobayashi, 1939. Origin The oldest known eodiscoid is '' Tsunyidiscus''. The glabella of ''Tsunyidiscus'' is extremely similar to that of ''Dipharus clarki'', and distinct from all other eodiscoids. ''D. clarki'' is thought to represent an immature stage of the redlichioid ''B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinodiscus
''Sinodiscus'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the late Atdabanian stage, which lasted from 530 to 524 million years ago during the early part of the Cambrian Period The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million .... Dai and Zhang (2013) were able to reconstruct both the morphology and ontogeny of ''S. changyangensis'' Zhang based on a large number of well preserved examples from the lower Cambrian Shuijingtuo Formation in Changyang, Hubei Province, South China. DAI, T., ZHANG, X. 2013. Morphology and ontogeny of the eodiscoid trilobite ''Sinodiscus changyangensis'' from the lower Cambrian of South China. ''Palaeontology'', 56, 2, 411 – 420. https://doi.org/10.1111/j.1475-4983.2012.01208.x References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsunydiscidae
''Tsunyidiscus'' is a trilobite belonging to the Suborder Eodiscina. ''Tsunyidiscus'' appeared near the end of the Lower Cambrian, during the late Atdabanian stage of geologic time and some collections suggest it may have survived into the Botomian. The genus is very small (up to 7mm), oculate and isopypous with a narrow dome-shaped glabella and a narrow bullet-shaped pygidial axis. Thorax consists of three segments. ''Tsunyidiscus'' is the only genus currently attributed to the family Tsunyidiscidae. Description Like other Agnostida the exoskeleton of ''Tsunyidiscus'' is diminutive and isopygous with 3 fulcrate thoracic segments. The cephalon has a strongly parabolic outline and maximum width (tr.) usually anterior to the genal angles. Glabella extremely narrow, lateral glabellar furrows usually obscure, with a rounded and expanded frontal glabellar lobe. The occipital ring (LO) is at least as long as L1, usually expanded laterally, and may bear a sharp posteriorly directed s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agnostida
Agnostida is an order of arthropod which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopoda. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders, and were highly diverse throughout the Cambrian. Agnostidan diversity severely declined during the Cambrian-Ordovician transition, and the last agnostidans went extinct in the Late Ordovician. Systematics The Agnostida are divided into two suborders — Agnostina and Eodiscina — which are then subdivided into a number of families. As a group, agnostids are isopygous, meaning their pygidium is similar in size and shape to their cephalon. Most agnostid species were eyeless. The systematic position of the order Agnostida within the class Trilobita remains uncertain, and there has been continuin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calodiscus
''Calodiscus'' is a genus of Eodiscinid trilobite in the family Calodiscidae. It lived during the late Lower Cambrian, with remains found in Canada (Newfoundland & Labrador), the United States (Massachusetts, New York State), Greenland, The United Kingdom (England), Sweden, France, Germany, Italy (Sardinia), Kazakhstan, the Russian Federation and China. The type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ... by original designation is ''Agnostus lobatus'' Hall, 1847 from the upper part of the lower Cambrian Browns Pond Formation (formerly Schodack Formation) at Troy in the Taconic region of New York State, USA ''Calodiscus korolevi'' Pokrovskaya ''in'' Ergaliev and Pokrovskaya, 1977; ''Calodiscus lakei'' Rasetti, 1952; and ''Calodiscus'' n. sp. A of Geyer, 1988, acco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Korobovia
''Korobovia'' Korovnikov, 2007, is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the later part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. Etymology The genus has been named after the Russian paleontologist M. N. Korobov. The species epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ... ''khorbosuonica'' refers to the Khorbosuonka River (a tributary of the Olenyok River), in the vicinity of which fossils of this species have been found. References * CEREGATO, A., RAFFI, S. & SCARPONI, D. (2006) ''The circa-littoral/bathyal paleocommunities in the Middle Pliocene of Northern Italy: The case of the Korobkovia oblonga - Jupi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Trilobites
The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian bio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobite Families
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period () and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described. By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, they left an extensive fossil record. The stu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pygidium
The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is composed of fused body segments, sometimes with a tail, and separated from thoracic segments by an articulation.Shultz, J.W. (1990). Evolutionary Morphology And Phylogeny of Arachnida. Cladistics 6: 1–38. Chelicerates In arachnids, the pygidium is formed by reduction of the last three opisthosomal segments to rings where there is no distinction between tergites and sternites. A pygidium is present in Palpigradi, Amblypygi, Thelyphonida, Schizomida, Ricinulei and in the extinct order Trigonotarbida. It is also present in early fossil representatives of horseshoe crabs. Trilobites In trilobites, the pygidium can range from extremely small (much smaller than the head, or cephalon) to larger than the cephalon. They can be smooth, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalon (arthropod Head)
The cephalon is the head section of an arthropod. It is a tagma, i.e., a specialized grouping of arthropod segments. The word cephalon derives from the Greek κεφαλή (kephalē), meaning "head". Insects In insects, ''head'' is a preferred term. The insect head consists of five segments, including three (the labial, maxillary and mandibular) necessary for food uptake, which are altogether known as the gnathocephalon and house the suboesophageal ganglion of the brain, as well as the antennal segment, and an ocular segment, as well as a non segmented fused section of the head where the archicerebrum is housed known as the acron. See also arthropod head problem. Chelicerates and crustaceans In chelicerates and crustaceans, the cephalothorax is derived from the fusion of the cephalon and the thorax, and is usually covered by a single unsegmented carapace. In relation with the arthropod head problem, phylogeny studies show that members of the Malacostraca class of crusta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Treatise On Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and extant (still living) invertebrate animals. The prehistoric invertebrates are described as to their taxonomy, morphology, paleoecology, stratigraphic and paleogeographic range. However, taxa with no fossil record whatsoever have just a very brief listing. Publication of the decades-long ''Treatise on Invertebrate Paleontology'' is a work-in-progress; and therefore it is not yet complete: For example, there is no volume yet published regarding the post-Paleozoic era caenogastropods (a molluscan group including the whelk and periwinkle). Furthermore, every so often, previously published volumes of the ''Treatise'' are revised. Evolution of the project Raymond C. Moor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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