Stylophora Kuehlmanni
The stylophorans are an extinct, possibly polyphyletic group allied to the Paleozoic Era echinoderms, comprising the prehistoric cornutes and mitrates. It is synonymous with the subphylum Calcichordata. Their unusual appearances have led to a variety of very different reconstructions of their anatomy, how they lived, and their relationships to other organisms. Stylophorans have played a major role in debates over the origin of chordates, as under the calcichordate hypothesis they were interpreted as being stem-group chordates. However, multiple lines of evidence argue against the calcichordate hypothesis, and stylophorans are now widely agreed to belong to the echinoderm total group. Debate remains over whether they are stem-group echinoderms which predate the origin of radial symmetry, or highly modified descendants of radially symmetric echinoderms. Description The general stylophoran body plan consists of a flattened theca and a single jointed appendage which extends from it. ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Middle Cambrian
Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (other) * Middle Brook (other) * Middle Creek (other) * Middle Island (other) * Middle Lake (other) * Middle Mountain, California * Middle Peninsula, Chesapeake Bay, Virginia * Middle Range, a former name of the Xueshan Range on Taiwan Island * Middle River (other) * Middle Rocks, two rocks at the eastern opening of the Straits of Singapore * Middle Sound, a bay in North Carolina * Middle Township (other) * Middle East Music *Middle (song), "Middle" (song), 2015 *The Middle (Jimmy Eat World song), "The Middle" (Jimmy Eat World song), 2001 *The Middle (Zedd, Maren Morris and Grey song), "The Middle" (Zedd, Maren Morris and Grey song), 2018 *"Middle", a song by Rocket from the Crypt from their 1995 album ''Scream, Dracula, Scream!'' *"The Middle ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Cothurnocystis
''Cothurnocystis'' is a genus of small enigmatic echinoderms that lived during the Ordovician. Individual animals had a flat boot-shaped body and a thin rod-shaped appendage that may be a stem, or analogous to a foot or a tail. Fossils of ''Cothurnocystis'' species have been found in Nevada, Scotland, Czech Republic, France and Morocco. Taxonomy The position of the Stylophora, of which ''Cothurnocystis'' is a prominent representative, has been in a state of flux. Some scientists claim to be able to see a structurally very basic notochord in the tail, and consequently consider the Stylophora to be a group of primitive chordates, calling them the "Calcichordata". Alternatively these animals are considered related to echinoderms, as the shell (or test (biology), test) is similar in structure and composition to the tests of echinoderms. However, stylophorans are asymmetric organisms that lack either the radial symmetry typical of most echinoderms, or the bilateral symmetry of the ch ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Edrioasteroidea
Edrioasteroidea is an extinct class of echinoderms. The living animal would have resembled a pentamerously symmetrical disc or cushion. They were obligate encrusters and attached themselves to inorganic or biologic hard substrates (frequently hardgrounds or brachiopods). A 507 million years old species, ''Totiglobus spencensis'', is actually the first known echinoderm adapted to live on a hard surface after the soft microbial mats that covered the seafloor were destroyed in the Cambrian substrate revolution. The oldest undisputed fossils of Edrioasteroidea are known from Cambrian (Stage 3, about 515-520 Ma ago) of Laurentia and are among the oldest known fossils of echinoderms. Some authors propose that an enigmatic Ediacaran (about 600 Ma) organism '' Arkarua'' is also an edrioasteroid, but this interpretation did not gain wide acceptance. Last edrioasteroids are known from Permian (Late Kungurian, about 270-280 Ma). Anatomy The body plan for this class was simple: a main body ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Calcichordate Theory
The calcichordate hypothesis, formulated by British Museum paleontologist Richard Jefferies, 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 has been disproven by the discovery that the "tail" of Stylophorans contains a water vascular system, ambulacrum, and tube feet. However, the clade Olfactores was first proposed as part of the calcichordate theory, and has since been validated through genetic sequencing, albeit without the involvement of mitrates. Details The carpoids Cornuta and Mitrate, Mitrata are grouped together in a clade called Calcichordata. Cornutes and mitrates are viewed as sister groups, and mitrates represent stem group chordates. The mitrates (and thus the chordates) are all dexiothetism, Dexiothetes, dexiothetism being a synapomorphy for the clade. Hypothetical phylogeny In t ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
List Of Echinodermata Orders
This List of echinoderm orders concerns the various classes and orders into which taxonomy (biology), taxonomists categorize the roughly 7000 extant species as well as the extinct species of the exclusively marine phylum Echinodermata. Subphylum Crinozoa Class Crinoidea * Subclass Articulata (Crinoidea), Articulata (540 species) ** Order Bourgueticrinida ** Order Comatulida ** Order Cyrtocrinida ** Order Hyocrinida ** Order Isocrinida ** Order Millericrinida * Subclass †Flexibilia * Subclass †Camerata (crinoid), Camerata * Subclass †Disparida Image:Comaster schlegelii.JPG, ''Comaster schlegelii'' (Comatulida) Image:Holopus 2.jpg, ''Holopus sp.'' (Cyrtocrinida) Image:Encrinus liliiformis 4.JPG, ''Encrinus liliiformis'' (Encrinida) Image:Calamocrinus diomedæ (Plate XXVIII) BHL4232451.jpg, ''Calamocrinus diomedae'' (Hyocrinida) Image:Proisocrinus ruberrimus.jpg, ''Proisocrinus ruberrimus'' (Isocrinida) Image:Liliocrinus polydactylus MHNT.jpg, ''Liliocrinus polydact ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Order (biology)
Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families. What does and does not belong to each order is determined by a taxonomist, as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely. The name of an order is usually written with a capital letter. For some groups of organisms, their orders may follow consist ... [...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 mollus ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Ambulacral
Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers. For example, sea stars or "star fish" have an ambulacral groove on their oral side (underside). This ambulacral groove extends from the mouth to the end of each ray or arm. Each groove of each arm in turn has four rows of hollow tube feet that can be extended or withdrawn. Opposite the ambulacral groove is an ambulacral ridge on the aboral side of each ray, known as an ambulacrum. These have interambulacra between them. Etymology From the Latin 'ambulācrum', meaning 'walk planted with trees', 'avenue', 'alley' and 'walking Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined as an " inverted pendulum" gait in which th ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Hemichordate
Hemichordata ( ) is a phylum which consists of triploblastic, eucoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and include two main classes: Enteropneusta (acorn worms), and Pterobranchia. A third class, Planctosphaeroidea, is known only from the larva of a single species, '' Planctosphaera pelagica''. The class Graptolithina, formerly considered extinct, is now placed within the pterobranchs, represented by a single living genus '' Rhabdopleura''. Acorn worms are solitary worm-shaped organisms. They generally live in burrows (the earliest secreted tubes) and are deposit feeders, but some species are pharyngeal filter feeders, while the family are free living detritivores. Many are well known for their production and accumulation of various halogenated phenols and pyrroles. Pterobranchs are filter-feeders, mostly colonial, living in a collagenous ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Simon Conway Morris
Simon Conway Morris (born 1951) is an English palaeontologist, evolutionary biologist, and astrobiologist known for his study of the fossils of the Burgess Shale and the Cambrian explosion. The results of these discoveries were celebrated in Stephen Jay Gould's 1989 book '' Wonderful Life''. Conway Morris's own book on the subject, ''The Crucible of Creation'' (1998), however, is critical of Gould's presentation and interpretation. Conway Morris, a Christian, holds to theistic views of biological evolution. He has held the Chair of Evolutionary Palaeobiology in the Department of Earth Sciences, University of Cambridge since 1995. Biography Early years Conway Morris was born on 6 November 1951. A native of Carshalton, Surrey, he was brought up in London, England. and went on to study geology at Bristol University, achieving a First Class Honours degree. He then moved to Cambridge University and completed a PhD at St John's College under Harry Blackmore Whittington. He ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Deuterostomes
Deuterostomes (from Greek: ) are bilaterian animals of the superphylum Deuterostomia (), typically characterized by their anus forming before the mouth during embryonic development. Deuterostomia comprises three phyla: Chordata, Echinodermata, Hemichordata, and the extinct clade Cambroernida. In deuterostomes, the developing embryo's first opening (the blastopore) becomes the anus and cloaca, while the mouth is formed at a different site later on. This was initially the group's distinguishing characteristic, but deuterostomy has since been discovered among protostomes as well. The deuterostomes are also known as enterocoelomates, because their coelom develops through pouching of the gut, enterocoely. Deuterostomia's sister clade is Protostomia, animals that develop mouth first and whose digestive tract development is more varied. Protostomia includes the ecdysozoans and spiralians, as well as the extinct ''Kimberella''. Together with the Xenacoelomorpha, these constitute t ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
|
Chordata
A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (Apomorphy and synapomorphy, synapomorphies) that distinguish them from other Taxon, taxa. These five synapomorphies are a notochord, a neural tube, hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post-anus, anal tail. In addition to the morphological characteristics used to define chordates, analysis of genome sequences has identified two conserved signature indels (CSIs) in their proteins: cyclophilin-like protein and inner mitochondrial membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cephalochordates. These CSIs provide molecular means to reliably distinguish chordates from all other animals. Chordates are divided into three phylum, subphyla: Vertebrata (fish, amphibians, reptiles, birds and mammals), whose notochor ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |