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Trilobites 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 20,000 species having been described.
Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among the earliest are Fallotaspis, and Lemdadella, both belonging to this order. The first representatives of the orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid species. In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters. The last redlichiid trilobites died out before the end of the Middle Cambrian.
Joscelin of Courtenay, Prince of Galilee and Lord of Turbessel (1115–1131) and Count of Edessa (1119–1131), ruled over the County of Edessa during its zenith, from 1118 to 1131. Captured twice, Joscelin continued to expand his county, even participating in the Battle of Azaz in 1125. Gravely injured during the collapse of a sapper mine, Joscelin marched his army to relieve the besieged fortress of Kaysun, and died soon after.
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.
Ceraurinella is an extinct genus of trilobite in the family Cheiruridae. There are about 19 described species in Ceraurinella.
Ronald Pearson Tripp FRSE was a British palaeontologist specializing in trilobites. He was self-taught in palaeontology and became an authority on the taxonomy of the trilobite order Lichida and the trilobite family Encrinuridae.
In anatomy, a suture is a fairly rigid joint between two or more hard elements of an organism, with or without significant overlap of the elements.
Sphaerexochus is a genus of trilobite from the Middle Ordovician to Late Silurian of Asia, Australia, Europe, and North America.
Aegrotocatellus is a genus of trilobite in the order Phacopida, which existed in what is now Nunavut, Canada. It was named by Adrain and Edgecombe in 1995, and the type species is Aegrotocatellus jaggeri, a species named after British musician Mick Jagger.
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.
Celtencrinurus is a genus of trilobites in the order Phacopida that existed during the upper Ordovician in what is now Northern Ireland. It was described by Evitt and Tripp in 1977, and the type species is Celtencrinurus multisegmentatus, which was originally described under the genus Amphion by Portlock in 1843. It was described from the Killey Bridge Formation.
Forteyops is a genus of trilobites in the order Phacopida, that existed during the lower Ordovician in what is now the United States. It was described by Pribyl and Vanek in 1985, and the type species is Forteyops sexapugia, which was originally described under the genus Kawina by Ross in 1951. The type locality was the Garden City Formation in Utah.
Hintzeia is a genus of trilobites in the order Phacopida, that existed during the lower Ordovician in what is now the United States. It was described by Harrington in 1957, and the type species is Hintzeia aemula, which was originally described under the genus Protopliomerops by Hintze in 1953. Harrington also moved two other Protopliomerops species, P. celsaora and P. firmimarginis, under Hintzeia. The generic name is derived from that of the type species' author. The type locality was the Fillmore Formation in Utah.
Lonchodomas is a genus of trilobites, that lived during the Ordovician. It was eyeless, like all raphiophorids, and had a long straight sword-like frontal spine, that gradually transforms into the relatively long glabella. Both the glabellar spine and the backward directed genal spines are subquadrate in section. Lonchodomas has five thorax segments and the pleural area of the pygidium has two narrow furrows. Lonchodomas occurred in what are today Argentina, Canada (Newfoundland), Estonia, Latvia, Norway, Sweden, the Russian Federation and the United States.
Ptychagnostus is a member of the agnostida that lived during the Cambrian period. Ptychagnostidae generally do not exceed one centimetre in length. Their remains are rarely found in empty tubes of the polychaete worm Selkirkia. The genus probably ranged throughout the water column. It has two glabellar lobes, and three pygidial lobes.
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".
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.
The Devonian Needmore Formation or Needmore Shale is a mapped bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.
Proetus is a genus of proetid trilobite found in Silurian-aged marine strata of Europe.
References
- ↑ Available Generic Names for Trilobites P.A. Jell and J.M. Adrain.
