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Asterozoa
The Asterozoa are a subphylum in the phylum Echinodermata. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the class Asteroidea (the starfish), the class Ophiuroidea (the brittle stars and basket stars), and the extinct order Somasteroidea. Taxonomy Asteroidea Members of the order Asteroidea are characterised by a star-shaped body plan consisting of a central disc and multiple radiating arms. They usually exhibit pentamerous radial symmetry, but some species typically have a symmetry based on a number other than five. The arms have very broad bases and their skeletal support is provided by the calcareous plates called ossicles or ambulacral plates in the body wall. These are joined with muscular and connective tissue giving flexibility. The mouth is on the lower or oral surface, with a corresponding anus on the upper or aboral surface; though the anus is absent in Paxillosida, wherein the mouth serves also as an an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cantabrigiaster Fezouataensis
''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 as '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Starfish
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-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] |
Asterozoa
The Asterozoa are a subphylum in the phylum Echinodermata. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the class Asteroidea (the starfish), the class Ophiuroidea (the brittle stars and basket stars), and the extinct order Somasteroidea. Taxonomy Asteroidea Members of the order Asteroidea are characterised by a star-shaped body plan consisting of a central disc and multiple radiating arms. They usually exhibit pentamerous radial symmetry, but some species typically have a symmetry based on a number other than five. The arms have very broad bases and their skeletal support is provided by the calcareous plates called ossicles or ambulacral plates in the body wall. These are joined with muscular and connective tissue giving flexibility. The mouth is on the lower or oral surface, with a corresponding anus on the upper or aboral surface; though the anus is absent in Paxillosida, wherein the mouth serves also as an an ... [...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 asteroidea, asteroids 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. Tree of Life Web Project. Retrieved 2011-09-29. According to the ''World Register of Marine Species'', Ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinodermata
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine phylum. The first definitive echinoderms appeared near the start of the Cambrian. The echinoderms are important both ecologically and geologically. Ecologically, there are few other groupings so abundant in the biotic desert of the deep sea, as well as shallower oceans. Most echinoderms are able to reproduce asexually and regenerate tissue, organs, and limbs; in some cases, they can undergo complete regeneration from a single lim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophiopetra Lithographica Aboral Larger 010813
''Ophiopetra'' is a genus of prehistoric brittle stars. It lived in lagoons A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ... in Solnhofen Plattenkalk Formation. It has only one known species, ''Ophiopetra lithographica''. Taxonomic history Both ''Ophiopetra'' and ''O. lithographica'' were first described by Raymond Enay and Hans Hess in 1962, who determined that the genus belonged to the order Chilophiurida Matsumoto, 1915 (later known as the infraorder Chilophiurina) and that it was related to the families Ophiodermatidae and Ophiochitonidae. In 1965, Hess then showed that the genus '' Aplocoma'' d'Orbigny, 1852 was related to ''Ophiopetra'', and proposed a new family, Aplocomidae Hess, 1965, for the two genera. In 2008, ''Ophiopetra'' and another genus, ''Ophiohybris'' He ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Stage 10
Stage 10 of the Cambrian is the still unnamed third and final stage of the Furongian series. It follows the Jiangshanian and precedes the Ordovician Tremadocian Stage. The proposed lower boundary is the first appearance of the trilobite '' Lotagnostus americanus'' around million years ago, but other fossils are also being discussed ( see below). The upper boundary is defined as the appearance of the conodont ''Iapetognathus fluctivagus'' which marks the beginning of the Tremadocian and is radiometrically dated as million years ago. Naming The 10th stage of the Cambrian has not been formally named by the ICS yet, although a number of local names exist. Several authors favor the name "Lawsonian" after Lawson Cove, in the Wah Wah Mountains of Utah. The lower part of the North American Skullrockian Stage corresponds roughly to the Cambrian Stage 10. Stratotype The ICS is still discussing which geological section and biostratigraphic marker will be used to define the base o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paxillosida
The Paxillosida are a large order of sea stars. Characteristics Paxillosida adults lack an anus and have no suckers on their tube feet. They do not develop the brachiolaria stage in their early development.Matsubara, M., Komatsu, M., Araki, T., Asakawa, S., Yokobori, S.-I., Watanabe, K. & Wada, H. (2005) The phylogenetic status of Paxillosida (Asteroidea) based on complete mitochondrial DNA sequences. Molecular Genetics and Evolution, 36, 598–605 They possess marginal plates, and have sessile pedicellariae. They mostly inhabit soft-bottomed environments of sand or mud. Systematics Recent analyses suggest Paxillosida may be a sister taxon of Asterina. The order is divided into these families: * family Astropectinidae Gray, 1840 * family Ctenodiscidae Sladen, 1889 * family Goniopectinidae Verrill, 1889 * family Luidiidae Sladen, 1889 * family Porcellanasteridae Sladen, 1883 * family Pseudarchasteridae * family Radiasteridae Fisher, 1916 File:Astropecten aranciacus Sardegn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. :E.g. '' Panthera leo'' (lion) and '' Panthera onca'' (jaguar) are two species within the genus '' Panthera''. ''Panthera'' is a genus within the family Felidae. The composition of a genus is determined by taxonomists. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: # monophyly – all descendants of an ancestral taxon are grouped together (i.e. phylogenetic analysis should cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tube Feet
Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on brittle stars, and have only a feeding function in feather stars. They are part of the water vascular system. Structure and function Tube feet function in locomotion, feeding, and respiration. The tube feet in a starfish are arranged in grooves along the arms. They operate through hydraulic pressure. They are used to pass food to the oral mouth at the center, and can attach to surfaces. A starfish that is inverted turns one arm over and attaches it to a solid surface, and levers itself the right way up. Tube feet allow these different types of animals to stick to the ocean floor and move slowly. Each tube foot consists of two parts: the ampulla and the podium. The ampulla is a water-filled sac contained in the body of the animal that co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Vascular System
The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. The system is composed of canals connecting numerous tube feet. Echinoderms move by alternately contracting muscles that force water into the tube feet, causing them to extend and push against the ground, then relaxing to allow the feet to retract. The exact structure of the system varies somewhat between the five classes of echinoderm. The system is part of the coelomic cavities of echinoderms, together with the haemal coelom (or haemal system), perivisceral coelom, gonadal coelom and perihaemal coelom. Other terms sometimes used to refer to the water vascular system are "ambulacral system" and "aquiferous system". In the past, "aquiferous system" was also used to refer to many unrelated invertebrate structures, but today, it is restricted to water channels in sponges and the hydrostatic skeleton of some mollu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
