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Acanthodian
Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which includes living sharks, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both osteichthyans (bony fish) and chondrichthyans (cartilaginous fish). In general body shape, they were similar to modern sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteians (gars, bowfins). A lower Silurian species, ''Fanjingshania renovata'', attributed to Climatiiformes is the oldest chondrichthyan with known anatomical features. The popular name "spiny sharks" is because they were superficially shark-shaped, with a streamlined body, paired fins, a strongly upturned tail, and stout, largely immovable bony spines supporting all the fins except the tail—hence, "spiny sharks". However, acan ... [...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] |
Acanthodes
''Acanthodes'' (from el, ἄκανθώδης , 'provided with spines') is an extinct genus of spiny shark. Fossils have been found in Europe, North America, Asia, and Australia. ''Acanthodes'' was most common in the Carboniferous and Early Permian. A few putative species ("''Acanthoides dublinensis", Acanthodes guizhouensis'') have been reported from Devonian strata, but their referral to the genus may not be valid. Description Compared with other spiny sharks, ''Acanthodes'' was relatively large, at long. The genus had no teeth, instead gills. Because of this, it is presumed to have been a filter feeder, filtering plankton from the water. The ''Acanthodes'' has been found to have only a couple of skull bones. It was covered in scales that were cubical in shape. It also had fewer spines than many of its relatives. Each of the paired pectoral and pelvic fins had a spine, as did the single anal and dorsal fins, giving it a total of just six, less than half that of many other spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnathostomata
Gnathostomata (; from Greek: (') "jaw" + (') "mouth") are the jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates, including humans. In addition to opposing jaws, living gnathostomes have true teeth (a characteristic which has subsequently been lost in some), paired appendages (pectoral and pelvic fins, arms, legs, wings, etc.), the elastomeric protein of elastin, and a horizontal semicircular canal of the inner ear, along with physiological and cellular anatomical characters such as the myelin sheaths of neurons, and an adaptive immune system that has the discrete lymphoid organs of spleen and thymus, and uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene. It is now assumed that Gnathostomata evolved from ancestors that already possessed a pair of both pectoral and pelvic fins. Until recently these ancestors, know ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gyracanthides
''Gyracanthides'' is an extinct genus of acanthodian gnathostome, known from Devonian to Early Carboniferous. Description ''Gyracanthides'' is large acanthodian, ''G. murrayi'' reached the length up to . The pectoral fin spines are large compared to its body, for specimen that have estimated to be had pectoral fin spines around long. A recent study suggested that ''Gyracanthides'' is closely related to chondrichthyans (as currently delimited), and that acanthodians Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which ... are paraphyletic. References Acanthodii genera Carboniferous acanthodians {{carboniferous-animal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diplacanthiformes
Diplacanthiformes (also known as Diplacanthida, Diplacanthoidei, or Diplacanthini) is an order of acanthodian fishes which lived during the Devonian Period. Subtaxa * ''incertae sedis'' ** Genus '' Bryantonchus'' ** Genus '' Culmacanthus'' ** Genus '' Devononchus'' ** Genus '' Striacanthus'' ** Genus ''Tetanopsyrus'' * Family Diplacanthidae ** Genus ''Diplacanthus ''Diplacanthus'' is an extinct genus of Mid to Late Devonian fish in the class Acanthodii, known as spiny sharks. Classification The genus was named by Louis Agassiz in 1843. It was formerly regarded as belonging to the Climatiformes but r ...'' ** Genus '' Milesacanthus'' ** Genus '' Ptychodictyon'' ** Genus '' Rhadinacanthus'' * Family Gladiobranchidae? ** Genus '' Gladiobranchus'' ** Genus '' Uraniacanthus''? References Acanthodii Prehistoric fish orders Devonian fish Devonian first appearances Devonian extinctions {{Acanthodii-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fanjingshania Renovata
''Fanjingshania'' is an extinct genus of acanthodian from the lower Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ... of China, making it currently the oldest known acanthodian. It comprises a single species, ''Fanjingshania renovata''. References {{Taxonbar, from=Q115766467 Acanthodii genera Silurian fish of Asia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diplacanthidae
''Diplacanthus'' is an extinct genus of Mid to Late Devonian fish in the class Acanthodii, known as spiny sharks. Classification The genus was named by Louis Agassiz in 1843. It was formerly regarded as belonging to the Climatiformes but recently reassigned to the Diplacanthiformes, in which it is united with, amongst others, ''Rhadinacanthu''s, '' Uraniacanthus'', and '' Culmacanthus''. Diplacanthiforms were widespread during the Middle and early Late Devonian. They are best represented in the Middle Devonian, by articulated fossils, fin spines, and abundant scales, the latter particularly from northern Europe. In a latest revision of the genus ''Diplacanthus,'' a large number of species from Europe were synonymized with earlier Scottish species, and these too were redefined. D. ''crassisimus'' was taken to have precedence over D. ''striatus'' as the name of the type specimen. ''Diplacanthus longispinus'' was reassigned to ''Rhadinacanthus longispinus'', within which were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthodiformes
Acanthodiformes is an order of acanthodian fishes which lived from the Early Devonian to Early Permian. Subtaxa * Family Acanthodidae ** Genus ''Acanthodes ''Acanthodes'' (from el, ἄκανθώδης , 'provided with spines') is an extinct genus of spiny shark. Fossils have been found in Europe, North America, Asia, and Australia. ''Acanthodes'' was most common in the Carboniferous and Early Perm ...'' ** Genus '' Acanthodopsis'' ** Genus '' Traquairichthys''? ** Genus '' Utahacanthus''? * Family Cheiracanthidae ** Genus '' Cheiracanthus'' ** Genus '' Fallodentus'' ** Genus '' Ginkgolepis'' ** Genus '' Haplacanthus'' ** Genus '' Homalacanthus''? ** Genus '' Markacanthus'' * Family Howittacanthidae ** Genus '' Halimacanthodes'' ** Genus '' Howittacanthes'' * Family Mesacanthidae ** Genus '' Lodeacanthus'' ** Genus '' Melanoacanthus'' ** Genus '' Mesacanthus'' ** Genus '' Promesacanthus'' ** Genus '' Teneracanthus'' ** Genus '' Triazeugacanthus''? References Aca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gyracanthidae
Gyracanthidae is an family of extinct fish belonging to the class Acanthodii, known from early Devonian to late Carboniferous. Members are characterized by large, broad-based, paired fin spines with the pectoral fin spines having a distinct longitudinal curvature. Although it is originally classified in order Climatiiformes The Climatiiformes is an order of extinct fish belonging to the class Acanthodii. Like most other "spiny sharks", the Climatiiformes had sharp spines. These animals were often fairly small in size and lived from the Late Silurian to the Early Ca ..., but later study questioned this. References Acanthodii Prehistoric fish families {{Carboniferous-animal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish Fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as seen in sharks. Apart from the tail or caudal fin, fish fins have no direct connection with the spine and are supported only by muscles. Their principal function is to help the fish swim. Fins located in different places on the fish serve different purposes such as moving forward, turning, keeping an upright position or stopping. Most fish use fins when swimming, flying fish use pectoral fins for gliding, and frogfish use them for crawling. Fins can also be used for other purposes; male sharks and mosquitofish use a modified fin to deliver sperm, thresher sharks use their caudal fin to stun prey, reef stonefish have spines in their dorsal fins that inject venom, anglerfish use the first spine of their dorsal fin like a fishing rod to lur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Richard Owen
Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Owen produced a vast array of scientific work, but is probably best remembered today for coining the word '' Dinosauria'' (meaning "Terrible Reptile" or "Fearfully Great Reptile"). An outspoken critic of Charles Darwin's theory of evolution by natural selection, Owen agreed with Darwin that evolution occurred, but thought it was more complex than outlined in Darwin's ''On the Origin of Species''. Owen's approach to evolution can be considered to have anticipated the issues that have gained greater attention with the recent emergence of evolutionary developmental biology. Owen was the first president of the Microscopical Society of London in 1839 and edited many issues of its journal – then known as ''The Microscopic Journal''. Owen also c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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