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Avonacanthus
''Avonacanthus'' is an extinct genus of cartilaginous fish from the lower Carboniferous. The name is derived from the type locality of Avon Gorge, near Bristol, England. It contains a single species, ''A. brevis'', which was originally regarded as a species of ''Ctenacanthus ''Ctenacanthus'' (from el, κτείς , 'comb' and el, ἄκανθα , 'spine') is an extinct genus of ctenacanthiform chondrichthyan. Remains have been found in the Bloyd Formation in Arkansas, United States (Carboniferous period) and in Sout ...''. It is currently known only from fin spines. It is probably a cladistically basal Heslerodid.Maisey, J. G. (2010). Heslerodidae (Chondrichthyes, Elasmobranchii), a new family of Paleozoic phalacanthous sharks. ''Kirtlandia'', ''57'', 13-21. References Elasmobranchii Prehistoric cartilaginous fish genera {{paleo-cartilaginous-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animalia
Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in which their body consists of a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from to . They have complex interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology. Most living animal species are in Bilateria, a clade whose members have a bilaterally symmetric body plan. The Bilateria include the protostomes, containing animals such as nematodes, arthropods, flatworms, annelids and molluscs, and the deuterostomes, containing the echinode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chordata
A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These five synapomorphies include a notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. The name “chordate” comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate structure and movement. Chordates are also Bilateral symmetry, bilaterally symmetric, have a coelom, possess a circulatory system, and exhibit Metameric, metameric segmentation. 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 mitochondrial inner membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cep ... [...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] |
Elasmobranchii
Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil. The definition of the clade is unclear with respect to fossil chondrichthyans. It has been used by different authors as equivalent to Neoselachii (the clade including modern sharks and rays and their last common ancestor) or for al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus comes above species and below family (taxonomy), 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 taxonomy (biology), 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Carboniferous
Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eighteen miles southwest of Gloucester and fifteen miles northeast of Bristol. Lower Wick is within the civil ... Gloucestershire, England See also * Nizhny {{Disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avon Gorge
The Avon Gorge () is a 1.5-mile (2.5-kilometre) long gorge on the River Avon in Bristol, England. The gorge runs south to north through a limestone ridge west of Bristol city centre, and about 3 miles (5 km) from the mouth of the river at Avonmouth. The gorge forms the boundary between the unitary authorities of North Somerset and Bristol, with the boundary running along the south bank. As Bristol was an important port, the gorge formed a defensive gateway to the city. On the east of the gorge is the Bristol suburb of Clifton, and The Downs, a large public park. To the west of the gorge is Leigh Woods, the name of both a village and the National Trust forest it is situated in. There are three Iron Age hill forts overlooking the gorge, as well as an observatory. The Clifton Suspension Bridge, an icon of Bristol, crosses the gorge. Geology and formation The gorge cuts through a ridge mainly of limestone, with some sandstone. This particular ridge runs from Cli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bristol
Bristol () is a city, ceremonial county and unitary authority in England. Situated on the River Avon, it is bordered by the ceremonial counties of Gloucestershire to the north and Somerset to the south. Bristol is the most populous city in South West England. The wider Bristol Built-up Area is the eleventh most populous urban area in the United Kingdom. Iron Age hillforts and Roman villas were built near the confluence of the rivers Frome and Avon. Around the beginning of the 11th century, the settlement was known as (Old English: 'the place at the bridge'). Bristol received a royal charter in 1155 and was historically divided between Gloucestershire and Somerset until 1373 when it became a county corporate. From the 13th to the 18th century, Bristol was among the top three English cities, after London, in tax receipts. A major port, Bristol was a starting place for early voyages of exploration to the New World. On a ship out of Bristol in 1497, John Cabot, a Venetia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ctenacanthus
''Ctenacanthus'' (from el, κτείς , 'comb' and el, ἄκανθα , 'spine') is an extinct genus of ctenacanthiform chondrichthyan. Remains have been found in the Bloyd Formation in Arkansas, United States (Carboniferous period) and in South America.Acanthodian fish remains from the Upper Silurian or Lower Devonian of the Amazon Basin, Brazil. Philippe Janvier, Jose Henrique G. Melo, Palaeontology, Aug 1988, Vol 31, part 3 Valid species * ''Ctenacanthus buttersi'' St. John & Worthen, 1883 * ''Ctenacanthus chemungensis'' Claypole, 1885 * ''Ctenacanthus concinnus'' Newberry, 1875 * ''Ctenacanthus denticulatus'' McCoy, 1848 * ''Ctenacanthus formosus'' Newberry, 1873 * ''Ctenacanthus harrissi'' Caster, 1930 * ''Ctenacanthus lamborni'' Wells, 1944 * ''Ctenacanthus major'' Agassiz, 1843 * ''Ctenacanthus pellensis'' St. John & Worthen, 1883 * ''Ctenacanthus sculptus'' St. John & Worthen, 1875 * ''Ctenacanthus terrelli'' Newberry, 1889 * ''Ctenacanthus tumidus'' Newberry, 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
