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Homostelea
Cincta is an extinct class of echinoderms that lived only in the Middle Cambrian epoch. Homostelea is a junior synonym. The classification of cinctans is controversial, but they are probably part of the echinoderm stem group. Cinctans were sessile, asymmetrical animals with a skeleton made of stereom plates and a racquet-shaped body composed of a theca and stele. They may have had a lifestyle similar to modern tunicates, filter-feeding by pumping water through gill slits in their pharynx. Description Cinctans were asymmetrical animals, though some species were nearly bilaterally symmetrical. Like all echinoderms, cinctans have a skeleton made of plates of stereom. The body of cinctans was divided into two sections, the main body, called the theca, and a posterior appendage called a stele. The overall shape of cinctans has been compared to a tennis racquet. The theca of cinctans was surrounded on its margins by a frame of large stereom plates called a cinctus, and the dorsal and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcichordate Hypothesis
The calcichordate hypothesis holds that each separate lineage of chordate (Cephalochordates, Urochordates, Craniates) evolved from its own lineage of mitrate, and thus the echinoderms and the chordates are sister groups, with the hemichordates as an out-group. It was formulated by British Museum paleontologist Dick Jefferies, Richard Jefferies. The hypothesis has been disproven as of 2019; exceptional preservation of soft tissues in the single appendage of the stylophorans ''Thoralicystis'' and ''Hanusia'' revealed clear traces consistent with a water vascular system—an ambulacral canal with tube feet—covered by movable plates, where the calcichordate hypothesis would require the anatomy be a tail containing a notochord protected by fixed plates. The enlarged area at the base of the appendage, which in the calcichordate hypothesis would contain muscles to move the tail, contains an extension of the body cavity. The findings also disprove the hypothesis that the group were stalked ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carpoid
Homalozoa is an obsolete extinct subphylum of Paleozoic era echinoderms, prehistoric marine invertebrates. They are also referred to as carpoids. Description The Homalozoa lacked the typical pentamer body form of other echinoderms, but all were sessile animals. Instead all Homalozoans were markedly asymmetric, and were extremely variable in forms. The body (theca) was covered with calcite plates with a number of openings. Their form is in some cases so unusual that it is unclear which openings are to be considered as mouth and anus. Many of them were stalked, similar to sea lilies (crinoids), but often their bodies were bent over, so that the mouth and anus projected forwards rather than upwards. Some forms, especially stylophorans, rested flat on the sea floor. In some forms the single ray ( brachiole or aulacophore) possessed an ambulacral groove. It has been claimed that some forms possessed gills and gill slits. Taxonomy Homalozoans were traditionally considered to be st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Miaolingian
The Miaolingian is the third Series of the Cambrian Period, and was formally named in 2018. It lasted from about to million years ago and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian. The Miaolingian is preceded by the unnamed Cambrian Series 2 and succeeded by the Furongian series. Definition A number of proposals for fossils and type sections were made before it was formally ratified in 2018. The most promising fossil markers were seen to be the respective first appearances of either trilobite species ''Ovatoryctocara granulata'' or ''Oryctocephalus indicus'', which both have an age close to million years ago. After some deliberation, the FAD of ''Oryctocephalus indicus'' was chosen to be the lower boundary marker, and the GSSP was placed in Wuliu-Zengjiayan, Guizhou, China. The Miaolingian-Furongian boundary has the same definition as the Paibian Stage. It is defined as the first appearance of ''Glyptagnostus reticulatus ''Glyptagn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ctenocystoidea
Ctenocystoidea is an extinct clade of echinoderms, which lived during the Cambrian and Ordovician periods. Unlike other echinoderms, ctenocystoids had bilateral symmetry, or were only very slightly asymmetrical. They are believed to be one of the earliest-diverging branches of echinoderms, with their bilateral symmetry a trait shared with other deuterostomes. Ctenocystoids were once classified in the taxon Homalozoa, also known as Carpoidea, alongside cinctans, solutes, and stylophorans. Homalozoa is now recognized as a polyphyletic group of echinoderms without radial symmetry. Ctenocystoids were geographically widespread during the Middle Cambrian, with one species surviving into the Late Ordovician. Description Like other echinoderms, ctenocystoids had a skeleton made of stereom plates. Ctenocystoids had near bilateral symmetry, with some species exhibiting slightly asymmetric plate shapes. Like cinctans and ''Ctenoimbricata'', most ctenocystoids had large marginal pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cystoids
Cystoidea is a class of extinct crinozoan echinoderms, termed cystoids, that lived attached to the sea floor by stalks. They existed during the Paleozoic Era, in the Middle Ordovician and Silurian Periods, until their extinction in the Devonian Period. Description Cystoids are distinguished from other echinoderms by triangular pore openings. Superficially, cystoids resembled crinoids, but they had an ovoid, rather than cup-shaped, body. The mouth was at the upper pole of the body, with the opposite end attached to the substratum, often by a stalk, although some stalkless species did exist. The anus lay on the side of the body. Five, or less commonly three, ambulacral areas ran along the outside of the body, radiating outwards from the mouth. A number of small tentacles either surrounded the mouth, or projected outwards in a row from the ambulacral areas, depending on species. The most distinctive feature of cystoids was the presence of a number of pores in the rigid skeleton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Regression
A marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land. Evidence of marine regressions and transgressions occurs throughout the fossil record, and the fluctuations are thought to have caused or contributed to several mass extinctions, such as the Permian-Triassic extinction event (250 million years ago) and Cretaceous–Paleogene extinction event (66 Ma). During the Permian-Triassic extinction, the largest extinction event in the Earth's history, the global sea level fell 250 m (820 ft). A major regression could itself cause marine organisms in shallow seas to go extinct, but mass extinctions tend to involve both terrestrial and aquatic species, and it is harder to see how a marine regression could cause widespread extinctions of land animals. Regressions are, therefore, seen as correlates or symptoms of major ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guzhangian
The Guzhangian is an uppermost stage of the Miaolingian Series of the Cambrian. It follows the Drumian Stage and precedes the Paibian Stage of the Furongian Series. The base is defined as the first appearance of the trilobite ''Lejopyge laevigata'' around million years ago. The Guzhangian-Paibian boundary is marked by the first appearance of the trilobite ''Glyptagnostus reticulatus'' around million years ago. The name Guzhangian is derived from Guzhang County, Hunan Province, China. The GSSP is defined in the Huaqiao Formation in Hunan. The precise base of the Guzhangian is a limestone layer 121.3 m above the base Huaqiao Formation(花桥组) at the Louyixi section (), where ''Lejopyge laevigata ''Lejopyge laevigata'' is a species of agnostid trilobite belonging to the genus '' Lejopyge''. It existed during the Guzhangian to the Paibian Age (around to million years ago) of the Cambrian. It has a cosmopolitan distribution and is an ...'' has its first appearance. R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Furongian
The Furongian is the fourth and final epoch and series of the Cambrian. It lasted from to million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocian Stage. It is subdivided into three stages: the Paibian, Jiangshanian and the unnamed 10th stage of the Cambrian. Naming The Furongian was also known as the Cambrian Series 4, and the name replaced the older term Upper Cambrian and equivalent to the local term Hunanian. The present name was ratified by the International Commission on Stratigraphy in 2003. () means ' lotus' in Mandarin and refers to Hunan which is known as the "lotus state". Definition The lower boundary is defined in the same way as the GSSP of the Paibian Stage. Both begin with the first appearance of the trilobite ''Glyptagnostus reticulatus'' around million years ago. The upper boundary is the lower boundary and GSSP of the Tremadocian Stage which is the first appearance of the conodont ''Iapetognathus f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drumian
The Drumian is a stage of the Miaolingian Series of the Cambrian. It succeeds the Wuliuan and precedes the Guzhangian. The base is defined as the first appearance of the trilobite ''Ptychagnostus atavus'' around million years ago. The top is defined as the first appearance of another trilobite ''Lejopyge laevigata'' around million years ago. The GSSP is defined in the ''Drumian section'' () in the Drum Mountains, Millard County, Utah, United States. The stage was also named after the Drum Mountains. The section is an outcrop of the Wheeler Formation The Wheeler Shale (named by Charles Walcott) is a Cambrian ( 507 Ma) fossil locality world-famous for prolific agnostid and ''Elrathia kingii'' trilobite remains (even though many areas are barren of fossils) and represents a Konzent ..., a succession of calcareous shales. The precise base of the Drumian is a laminated limestone above the base of the Wheeler Formation. References Cambrian geochronology Geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blastozoa
Blastozoa is a subphylum of extinct animals belonging to Phylum Echinodermata. This subphylum is characterized by the presence of specialized respiratory structures and brachiole plates used for feeding. This subphylum ranged from the Cambrian to the 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 .... References External linksHarvard: Subphylum Blastozoa Paleozoic echinoderms Cambrian echinoderms Silurian echinoderms Ordovician echinoderms Devonian echinoderms Permian echinoderms Animal subphyla {{paleo-echinoderm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleurocystites
''Pleurocystites'' (meaning ''rib bag'' or ''side bladder'') is a genus of rhombiferan echinoderm (a cystoid) that lived in the Late Ordovician. Its fossils are known from Europe and North America. ''Pleurocystites'' grew to a height of 2 centimeters (3/4 of an inch) and fed on plankton. Sources * ''Fossils'' (Smithsonian Handbooks) by David Ward (Page 191) * Parker, Steve. Dinosaurus: the complete guide to dinosaurs. Firefly Books Inc, 2003. Pg. 75 External links''Pleurocystites''in the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ... Rhombifera Ordovician echinoderms of Europe Ordovician echinoderms of North America Late Ordovician first appearances Late Ordovician extinctions Paleozoic life of Ontario Paleozoic life of Quebec {{pale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gogia
''Gogia'' is a genus of primitive eocrinoid blastozoan from the early to middle Cambrian. ''G. ojenai'' dates to the late Early Cambrian; other species come from various Middle Cambrian strata throughout North America, but the genus has yet to be described outside this continent. Notable localities where species are found include the Wheeler Shale of Utah, and the Burgess Shale of British Columbia. The species of ''Gogia'', like other eocrinoids, were not closely related to the true crinoids, instead, being more closely related to the blastoids. ''Gogia'' is distinguished from sea lilies, and most other blastoids, in that the plate-covered body was shaped like a vase, or a bowling pin (with the pin part stuck into the substrate), and that the five ambulacra were split into pairs of coiled or straight, ribbon-like strands. Six specimens of ''Gogia'' are known from the Greater Phyllopod bed The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
