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Asterozoa
The Asterozoa are a subphylum in the phylum Echinodermata, within the Eleutherozoa. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the classes Asteroidea (the starfish or sea stars), Ophiuroidea (the brittle stars and basket stars), Somasteroidea (early asterozoans from which the other classes most likely evolved), and Stenuroidea (early asterozoans with unclear relationships to extant classes). A fifth class, Concentricycloidea, was proposed for the unusual genus '' Xyloplax'' (sea daisies), but was later demoted to the status of infraclass as the sister of Neoasteroidea within the asteroidean sublcass Ambuloasteroidea. Taxonomy Asterozoa was originally proposed in the late 1800s, but was not used in F.A. Bather's two-subphylum echinoderm taxonomy in 1900. However, it was adopted as part of a four-subphylum taxonomy by the '' Treatise on Invertebrate Paleontology'' in 1966. Asterozoa is generally thought t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinodermata
An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry (pentamerous symmetry), and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine animal, marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian. Echinoderms are important both ecologically and geologically. Ecologically, there are few other groupings so abundant in the deep sea, as well as continental shelf, shallower oceans. Most echinoderms are able to asexual reproduction, reproduce asexually and regeneration (biology), regenerat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asterozoa
The Asterozoa are a subphylum in the phylum Echinodermata, within the Eleutherozoa. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the classes Asteroidea (the starfish or sea stars), Ophiuroidea (the brittle stars and basket stars), Somasteroidea (early asterozoans from which the other classes most likely evolved), and Stenuroidea (early asterozoans with unclear relationships to extant classes). A fifth class, Concentricycloidea, was proposed for the unusual genus '' Xyloplax'' (sea daisies), but was later demoted to the status of infraclass as the sister of Neoasteroidea within the asteroidean sublcass Ambuloasteroidea. Taxonomy Asterozoa was originally proposed in the late 1800s, but was not used in F.A. Bather's two-subphylum echinoderm taxonomy in 1900. However, it was adopted as part of a four-subphylum taxonomy by the '' Treatise on Invertebrate Paleontology'' in 1966. Asterozoa is generally thought t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eleutherozoa
Eleutherozoa is a subphylum of echinoderms. They are mobile animals with the mouth directed towards the substrate. They usually have a madreporite, tube feet, and moveable spines of some sort. It includes all living echinoderms except for crinoids. The monophyly of Eleutherozoa has been proven sufficiently well to be considered "uncontroversial." Etymology From Ancient Greek ἐλεύθερος (eleútheros, “free”) + ζῷον (zôion, “animal”), meaning "animal that moves freely." Classification History Originally defined by F. J. Bell in a sense that excluded Holothuroidea, Eleutherozoa was expanded by F. A. Bather in his 1900 taxonomy to include all free-living echinoderms. Bather considered the taxa within Eleutherozoa to have descended from the other subphylum in his two-subphylum system, the Pelmatozoa, either from different subgroups or at "widely different periods." In cladistic terms, this would make Eleutherozoa a polyphyletic group. In 1966–7, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Villebrunaster
''Villebrunaster'' is an extinct genus of starfish-like animal belonging to Asterozoa that lived around 480 million years ago during Early Ordovician Period in modern-day southern France and Morocco. As of 2022, it contains two species, namely ''V. thorali'' and ''V. fezouataensis''. ''V. thorali'' was described in 1951 and ''V. fezouataensis'' was described in 2021. ''Villebrunaster'' represents one of the oldest members of asterozoans, and perhaps, according to a description in 2021, the earliest divergent stem-group (ancestral members) of Asterozoa. Discovery and species The first species was discovered and described by British palaeontologist William Kingdon Spencer in 1951. The fragmentary specimens were collected from Saint-Chinian Formation in southern France. Spencer recognised it as among "the earliest starfish known." Another British palaeontologist, Juliette Dean Shackleton, identified new specimens as ''Ampullaster ubaghsi'' in 2005, which were later reclassified a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroidea
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at below the surface. Starfish are marine invertebrates. They typically have a central disc and usually five arms, though some species have a larger number of arms. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown. Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surfa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Starfish
Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropics, tropical zones to frigid, polar regions of Earth, polar regions. They are found from the intertidal zone down to abyssal zone, abyssal depths, at below the surface. Starfish are marine invertebrates. They typically have a central disc and usually five arms, though some species have a larger number of arms. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown. Starfish have tube fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stelleroidea
Stelleroidea is a junior synonym of Asterozoa. History In 1900, Stelleroidea was included as a class in F. A. Bather's echinoderm taxonomy, which grouped Asteroidea and Ophiuroidea within it as subclasses due to their Paleozoic history. In 1966, the ''Treatise on Invertebrate Paleontology'' included Stelleroidea as the only class within the subphylum Asterozoa The Asterozoa are a subphylum in the phylum Echinodermata, within the Eleutherozoa. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the classes Asteroidea (the starfish or sea stars), ..., with Somasteroidea, Asteroidea, and Ophiuroidea as subclasses. By a 1980 revision of the ''Treatises taxonomy, Asteroidea and Ophiuroidea had been promoted to classes in place of Stelleroidea. References Works cited * * * Superclasses (biology) Echinoderm taxonomy {{echinoderm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Somasteroidea
The Somasteroidea, or Stomasteroidea, is an extinct order of asterozoan echinoderms first defined in 1951 by W. K. Spencer.W. K. Spencer. (1951). Early Palaeozoic starfish. ''Philosophical Transactions of the Royal Society of London, series B'' 235(B623):87-129 Their first appearance in the fossil record was in the Early Ordovician (Tremadocian) and they had become extinct by the Late Devonian (Famennian). They are similar to the asteroids An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ... in that their bodies are flattened dorsoventrally and they have five petaloid arms with broad bases. The ambulacral plates in somasteroids are simple and unspecialized, and the arms were thought to be not flexible and were unable to assist in feeding, but the oral mouth parts were more complex. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Treatise On Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authored work of currently 55 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, when needed, previously published vol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Francis Arthur Bather
Francis Arthur Bather FRS (17 February 1863, in Richmond upon Thames – 20 March 1934) was a British palaeontologist, geologist and malacologist. His mother, Lucy Elizabeth Blomfield, was a daughter of Charles Blomfield, Bishop of London. His father, Arthur Henry Bather, who was deaf, was a clerk in the office of the Accountant-General for the Navy. Bather joined the Department of Geology at the Natural History Museum in 1887. He became Keeper in succession to Arthur Smith Woodward in 1924, retiring in 1928. Bather was awarded the Lyell Medal of the Geological Society, of which he also served as president. He was an Honorary Member of the Royal Geological Society of Cornwall, and was elected a fellow of the Royal Society in 1909. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1928. In 1932 Bather was awarded the Mary Clark Thompson Medal from the National Academy of Sciences. He married Stina Bergöö, daughter of Adolf Bergöö of S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ossicle (echinoderm)
Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines (which are specialised sharp ossicles) are the only parts of the animal likely to be fossilized after an echinoderm dies. Formation Ossicles are created intracellularly by specialised secretory cells known as sclerocytes in the dermis of the body wall of echinoderms. Each ossicle is composed of microcrystals of calcite arranged in a three-dimensional lattice known as a stereom. Under polarized light the ossicle behaves as if it were a single crystal because the axes of all the crystals are parallel. The space between the crystals is known as the stroma (animal tissue), stroma and allows entry to sclerocytes for enlargement and repair. The honeycomb structure is light but tou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crinoidea
Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths of over . Adult crinoids are characterised by having the mouth located on the upper surface. This is surrounded by feeding arms, and is linked to a U-shaped gut, with the anus being located on the oral disc near the mouth. Although the basic echinoderm pattern of fivefold symmetry can be recognised, in most crinoids the five arms are subdivided into ten or more. These have feathery pinnules and are spread wide to gather planktonic particles from the water. At some stage in their lives, most crinoids have a short ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
