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Trilobites are a group of extinct marine arachnomorph 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 Proetids 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 300 million years.
Asaphida is a large, morphologically diverse order of trilobites found in marine strata dated from the Middle Cambrian until their extinction during the Silurian. Asaphida contains six superfamilies, but no suborders. Asaphids comprise some 20% of described fossil trilobites.
Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in the second half of the Lower Cambrian, and the last species did not survive the Ordovician–Silurian extinction event.
Corynexochida is an order of trilobite that lived from the Lower Cambrian to the Late Devonian. Like many of the other trilobite orders, Corynexochida contains many species with widespread characteristics.
Phacops is a genus of trilobites in the order Phacopida, family Phacopidae, that lived in Europe, northwestern Africa, North and South America and China from the Late Ordovician until the very end of the Devonian, with a broader time range described from the Late Ordovician. It was a rounded animal, with a globose head and large eyes, and probably fed on detritus. Phacops is often found rolled up ("volvation"), a biological defense mechanism that is widespread among smaller trilobites but further perfected in this genus.
The Emu Bay Shale is a geological formation in Emu Bay, South Australia, containing a major Konservat-Lagerstätte. It is one of two in the world containing Redlichiidan trilobites. The Emu Bay Shale is dated as Cambrian Series 2, Stage 4, correlated with the upper Botomian Stage of the Lower Cambrian.
Isotelus is a genus of asaphid trilobites from the middle and upper Ordovician period, fairly common in the Northeastern United States, northwest Manitoba, southwestern Quebec and southeastern Ontario. One species, Isotelus rex, is currently the world's largest trilobite ever found as a complete fossil.
Calymenesum is a trilobite in the order Phacopida that existed in what is now China during the middle Ordovician. It was described by Kobayashi in 1951, and the type species is Calymenesum tingi, originally described under the genus Calymene by Sun in 1931. The species was described from the Shistzupu Formation in Guizhou, China.
Chasmops is a trilobite in the order Phacopida that existed during the upper Ordovician in what is now Estonia. It was described by McCoy in 1849, and the type species is Chasmops odini, which was originally described under the genus Calymene by Eichwald in 1840. It also contains the species C. maxima.
Coronura is a trilobite in the order Phacopida, that existed during the Middle Devonian in what is now New York, U.S.A. It was described by Hall and Clarke in 1888, and the type species is Coronura aspectans, which was originally described under the genus Asaphus by Conrad in 1841. The species was described from the Onondaga Formation. Fossils of Coronura have also been found in Indiana, and in the Emsian to Givetian Floresta Formation, Altiplano Cundiboyacense, Colombia.
Cromus is a genus of phacopid trilobites in the family Encrinuridae, that existed during the upper Silurian in what is now the Czech Republic. The genus was described by Barrande in 1852, and the type species is C. intercostatus. It also contains the species C. canorus.
Encrinuroides is a genus of trilobites in the order Phacopida, that existed during the upper Ordovician in what is now Wales. It was described by Reed in 1931, and the type species is Encrinuroides sexcostata, which was originally described under the genus Cybele by Salter in 1848. It also contains the species, Encrinuroides enshiensis, Encrinuroides insularis, and Encrinuroides rarus. The type locality was in the Sholeshook Limestone Formation.
Kanoshia is a genus of trilobites in the order Phacopida, that existed during the middle Ordovician in what is now Utah, USA. It was described by Harrington in 1957, and the type species is Kanoshia kanoshensis, which was originally described under the genus Pseudomera by Hintze in 1953. It also contains the species K. depressus and K. reticulata. The generic name is derived from the type species' epithet, which in turn is derived from the name of the type locality, the Kanosh Formation.
Calymenidae is a family of trilobites, containing the following genera:
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".
Micragnostus is a genus of trilobite in the order Agnostida, which existed in what is now north Wales. It was described by Howell in 1935, and the type species is Micragnostus calvus, which was originally described as a species of Agnostus by Lake in 1906.
Phalacroma is a genus of trilobite in the order Agnostida, which existed in what is now the Czech Republic. It was described by Hawle and Corda in 1867, and the type species is Phalacroma bibullatus, which was originally described as a species of Battus by Barrande in 1846.
Bumastus is an extinct genus of corynexochid trilobites which existed from the Early Ordovician period to the Late Silurian period. They were relatively large trilobites, reaching a length of 6 in (15 cm). They were distinctive for their highly globular, smooth-surfaced exoskeleton. They possessed well-developed, large compound eyes and were believed to have dwelled in shallow-water sediments in life.
Raymondaspis is a genus of trilobites in the family Styginidae. It was described by Pribyl in 1949, and contains the species R. reticulatus and R. turgidus from the Whiterockian of Canada, R. vespertina from the Ordovician and Whiterockian of the United States and Norway, and a new species, R. grandigena, which existed during the Middle Ordovician of what is now Sweden. R. grandigena was described in 2012 by Martin Stein and Jan Bergström.
The Letná Formation is a Late Ordovician geologic formation of the Prague Basin, Bohemian Massif in the Czech Republic. The formation crops out in the Czech capital, more specifically at Letná Hill, after which the formation is named. The type locality is located at Malá Strana, Holešovice district.
References
- ↑ Available Generic Names for Trilobites P.A. Jell and J.M. Adrain.
