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Eugeneodontida
The Eugeneodontida is an extinct and poorly known order of cartilaginous fishes. They possessed "tooth-whorls" on the symphysis of either the lower or both jaws and pectoral fins supported by long radials. They probably lacked pelvic fins and anal fins. The palatoquadrate was either fused to the skull or reduced. Now determined to be within the Holocephali, their closest living relatives are ratfish. The eugeneodonts are named after paleontologist Eugene S. Richardson, Jr. The Eugeneodontida disappeared in the Early Triassic. Members of the Eugeneodontida are further classified into different families, the most well-preserved members that have been discovered are commonly placed within the families Helicoprionidae ("spiral saws"), and Edestidae ("those which devour"), the former containing the genera ''Helicoprion'', '' Sarcoprion'', and '' Parahelicoprion'', and the latter containing the genera '' Edestus'', ''Lestrodus'', and '' Metaxyacanthus''. All eugeneodonts are thought ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caseodontoidea
The Eugeneodontida is an extinct and poorly known order of cartilaginous fishes. They possessed "tooth-whorls" on the symphysis of either the lower or both jaws and pectoral fins supported by long radials. They probably lacked pelvic fins and anal fins. The palatoquadrate was either fused to the skull or reduced. Now determined to be within the Holocephali, their closest living relatives are ratfish. The eugeneodonts are named after paleontologist Eugene S. Richardson, Jr. The Eugeneodontida disappeared in the Early Triassic. Members of the Eugeneodontida are further classified into different families, the most well-preserved members that have been discovered are commonly placed within the families Helicoprionidae ("spiral saws"), and Edestidae ("those which devour"), the former containing the genera ''Helicoprion'', '' Sarcoprion'', and '' Parahelicoprion'', and the latter containing the genera '' Edestus'', ''Lestrodus'', and '' Metaxyacanthus''. All eugeneodonts are thought ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicoprion
''Helicoprion'' is an extinct genus of shark-like eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extinct cartilaginous fish, the skeleton is mostly unknown. Fossils of ''Helicoprion'' are known from a 20 million year timespan during the Permian period from the Artinskian stage of the Cisuralian (Early Permian) to the Roadian stage of the Guadalupian (Middle Permian). The closest living relatives of ''Helicoprion'' (and other eugeneodonts) are the chimaeras, though their relationship is very distant. The unusual tooth arrangement is thought to have been an adaption for feeding on soft bodied prey, and may have functioned as a deshelling mechanism for hard bodied cephalopods such as nautiloids and ammonoids. In 2013, systematic revision of ''Helicoprion'' via morphometric analysis of the tooth whorls found only ''H. davisii, H. bessonowi'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocephali
Holocephali ("complete heads"), sometimes given the term Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. Little is known about these primitive forms, and the only surviving group in the subclass is the order Chimaeriformes. Chimaeriformes, commonly known as chimaeras, includes the rat fishes in the genus '' Chimaera'', and the elephant fishes in the genus ''Callorhinchus''. These fishes move by using sweeping movements of their large pectoral fins. They are deep sea fish with slender tails, living close to the seabed to feed on benthic invertebrates. They lack a stomach, their food moving directly into the intestine. Extinct holocephalans were much more diverse in lifestyles, including shark-like predatory forms and slow, durophagous fish. Characteristics Members of this taxon preserve today some features of elasmobranch life in Paleozoic times, though in other respects th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicoprionidae
The Helicoprionidae, also known as the Agassizodontidae are an extinct, poorly known family of bizarre holocephalids within the poorly understood order Eugeneodontida. Members of the Helicoprionidae possessed a unique "tooth-whorl" on the symphysis of the lower jaw and pectoral fins supported by long radials. The closest living relatives of the Helicoprionidae and all other eugeneodontids are the ratfishes. The anatomy of the tooth-whorl differed amongst genus and species, some possessing complete spirals (such as those of ''Helicoprion ''Helicoprion'' is an extinct genus of shark-like eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extin ...''), others possessing halved spirals (seen in '' Parahelicoprion''), and some with wedged half-spirals (seen in '' Sarcoprion''). Each tooth-whorl is thought to be adapted to a different type of p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edestus
''Edestus'' is an extinct genus of edestoid cartilaginous fish known from the Late Carboniferous ( Pennsylvanian) of the United Kingdom, Russia, and the United States. Most remains consist of isolated curved blades or "whorls" that are studded with teeth, that in life were situated within the jaws. ''Edestus'' is a Greek name derived from the word ''edeste'' (to devour), in reference to the aberrant quality and size of the species' teeth. The largest species, ''E. heinrichi'', has been conservatively estimated to reach greater than 6.7 m (22 ft) in length, around the size of the largest known great white shark. Like its other relatives, such as ''Helicoprion'', and unlike modern sharks, the species of ''Edestus'' grew teeth in curved blades or "whorls". In ''Edestus''' case, only a single row of teeth occurred in the midline of each jaw, leading ''Edestus'' to sometimes be described as the "scissor tooth shark". The degree of curvature in the teeth brackets, along with s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chondrichthyes
Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. Chondrichthyes are jawed vertebrates with paired fins, paired nares, scales, and a heart with its chambers in series. Extant chondrichthyes range in size from the 10 cm (3.9 in) finless sleeper ray to the 10 m (32 ft) whale shark. The class is divided into two subclasses: Elasmobranchii (sharks, rays, skates, and sawfish) and Holocephali ( chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates. Anatomy Skeleton The skeleton is cartilaginous. The notochord is gradually replaced by a vertebral column during development, except in Holocephali, where the notochord stays intact. In some deepwat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Campodus
''Campodus'' is an extinct genus of eugeneodont holocephalans from the Carboniferous. Likely one of the earliest and most basal caseodontoids, it can be characterized by its broad, ridge-ornamented crushing teeth made of various types of dentine. The type species, ''C. agassizianus'', was originally described in 1844 based on a small number of teeth from the Namurian of Belgium. Additional fossils have been referred to the genus. These include Belgian specimens referred by Lohest (1884), fossils from Missouri referred by Zangerl (1981), and symphyseal tooth-whorls from Nebraska and Kansas referred by Eastman (1902). The tooth whorls were given their own species, ''C. variabilis''. They shared some similarity to a massive "'' Agassizodus''" jaw apparatus found in Osage, Kansas and described by St. John & Worthen (1875). This has led some authors to the conclusion that ''Agassizodus'' and ''Campodus'' were synonyms. However, others note that clearly identifiable ''Campodus'' t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bobbodus
''Bobbodus'' is an extinct genus of eugeneodont shark from the Carboniferous and Permian periods. ''B. schaefferi'' is the type species and is known from three specimens, all from what was the eastern coast of the Panthallasic Ocean. They were found in the Kasimovian of Iowa, Gzhelian of Nebraska, Asselian of Kansas. Specimens of this species show the partial upper and lower dentition, the palatoquadrate, and gill arch. ''B. xerxesi'' is known from a single tooth found in Wuchiapingian-aged deposits in the Baghuk Mountains of central Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni .... It is named for Xerxes, a famous Archaemenid ruler from the area whose monuments impressed the first author of the paper describing it.Hampe, O., Hairapetian, V., Dorka, M., Witzmann, F., Akb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fadenia
''Fadenia'' is an extinct genus of eugeneodontid holocephalian chondrichthyan from the Carboniferous Period of Missouri (United States), the Permian period of Greenland, and the Early Triassic epoch of Greenland and Sulphur Mountain Formation of British Columbia, Canada. Eugeneodontida are an extinct order of Chondrichthyes. They are characterized by the presence of tooth whorls. They include iconic genera, such as ''Helicoprion'' (buzz-saw shark), '' Ornithoprion'', '' Edestus'' or '' Caseodus''. ''Fadenia'' is one of the few eugeneodontid genera that survived the end-Permian mass extinction event. It is one of the last surviving genera of this clade. It could reach about in length. The first fossils of Fadenia were discovered and written about in the periodical Meddelelser om Grønland in 1932 by the Danish vertebrate palaeontologist Eigil Nielsen after studying the Upper Permian beds of Cape Stosch, in the fjord of Godthab Gulf in King Christian X Land, Greenland. He had ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edestidae
The Edestidae are a poorly known, extinct family of shark-like eugeneodontid holocephalid cartilaginous fish. Similar to the related family Helicoprionidae, members of this family possessed a unique "tooth-whorl" on the symphysis of the lower jaw and pectoral fins supported by long radials. In addition to having a tooth-whorl on the lower jaw, at least one species of the genus ''Edestus'' had a second tooth-whorl in the upper jaw. The palatoquadrate was either fused to the skull or reduced. Edestids, along with the rest of the Eugeneodontida, are placed within the Holocephali.Tapanila, L., Pruitt, J., Pradel, A., Wilga, C., Ramsay, J., Schlader, R., Didier, D. 2013. Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion. Biology Letters. 10.1098/rsbl.2013.0057 The family disappeared in the Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parahelicoprion
''Parahelicoprion'' is an extinct genus of shark-like eugeneodontid holocephalids from the Permian of the Ural Mountains (Russia) and Copacabana Formation, Bolivia. The genus name, from "nearly coiled saw" in Greek, directly refers to ''Helicoprion'', a related holocephalid that shares similar traits to it, including the helical whorl of teeth. Description One of the primary qualities that separate ''Parahelicoprion'' from ''Helicoprion'' is the shape, thickness, and angle of the tooth whorl. Its teeth protrude outwards not like a tightly coiled saw, but instead a curved arrangement of cutting blades indicating it relied less on crushing slow-moving invertebrates and catching cephalopods, or other small mollusk prey, but inflicting traumatic damage against more durable, faster prey. Their teeth grew at a much slower pace than those of other whorl-tooth sharks, resulting in a depreciated spiral, growing only half of the teeth a ''Helicoprion'' would grow in its lifetime. The to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caseodus
''Caseodus'' is an extinct genus of eugeneodontid holocephalian from the Carboniferous of the United States (Illinois, Indiana, Kansas, South Dakota) and the Early Triassic of Canada (British Columbia). It was of medium size, measuring in length. Eugeneodontida are an extinct order of Chondrichthyes. They are characterized by the presence of tooth whorls. They include iconic genera, such as ''Helicoprion'' ("buzz-saw shark"), ''Ornithoprion'', '' Edestus'' or '' Fadenia''. ''Caseodus'' is one of the few eugeneodontid genera that survived the end-Permian mass extinction event. It is one of the last surviving genera of this clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, .... ''Caseodus'' is named after the late paleoichthyologist Gerard Case. References * Caseodo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
