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Acanthodian
Acanthodii or acanthodians is an extinct class of Gnathostomata, gnathostomes (jawed fishes). They are currently considered to represent a paraphyletic Evolutionary grade, grade of various fish lineages Basal (phylogenetics), basal to extant taxon, extant Chondrichthyes, which includes living sharks, Batoidea, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both Osteichthyes, osteichthyans (bony fish) and chondrichthyans (cartilaginous fish). In general body shape, they were similar to modern sharks, but their Epidermis (skin), epidermis was covered with tiny rhomboid platelets like the scales of holosteians (gars, bowfins). The popular name "spiny sharks" is because they were superficially shark-shaped, with a streamlined body, paired Fish fin, fins, a strongly upturned tail, and stout, largely immovable bony spines supporting all the fins except the tail—hence, "spiny sharks". However, acanthodians are not true sharks; their close relation to modern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Acanthodiformes
Acanthodiformes (alternatively spelled Acanthodida) is an Order (biology), order of "Acanthodii, acanthodians" which lived from the Early Devonian to the Early Permian. Members of the order have been found Cosmopolitan distribution, worldwide in rocks preserving both Freshwater fish, freshwater and Saltwater fish, marine environments, and are distinguished from other acanthodians by the presence of only a single dorsal fin and dorsal fin spine, and in most members a lack of Tooth, teeth and well-developed Gill raker, gill rakers. Some acanthodiforms are presumed to have fed by Filter feeder, filter-feeding, and had large mouths and Branchial arch, gill arches. While they have been suggested to be close relatives of modern Osteichthyes, bony fish due to similarities in their skulls, recent research indicates that, like other acanthodians, they are more likely to be stem-group Chondrichthyes, cartilaginous fish. Classification The order was first established by Soviet Union, Sovie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Gnathostomata
Gnathostomata (; from Ancient Greek: (') 'jaw' + (') 'mouth') are jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all extant vertebrates, including all living bony fishes (both ray-finned and lobe-finned, including their terrestrial tetrapod relatives) and cartilaginous fishes, as well as extinct prehistoric fish such as placoderms and acanthodians. Most gnathostomes have retained ancestral traits like true teeth, a stomach, and paired appendages ( pectoral and pelvic fins, limbs, wings, etc.). Other traits are elastin, horizontal semicircular canal of the inner ear, myelinated neurons, and an adaptive immune system which has discrete secondary lymphoid organs (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 two pairs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Chondrichthyes
Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates. 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). Extant chondrichthyans range in size from the finless sleeper ray to the over whale shark. Anatomy Skeleton The skeleton is cartilaginous. The notochord is gradually replaced by a vertebral column during development, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Nerepisacanthus
''Nerepisacanthus'' is an extinct genus of acanthodian, probably Acritolepidae, acritolepid, from Middle Silurian (?late Llandovery epoch, Llandovery (Telychian) to Ludlow epoch, Ludlow stages) deposits of New Brunswick, Canada. ''Nerepisacanthus'' is known from many incomplete but articulated specimens. It was collected from the Cunningham Creek Formation, near Nerepis, southern New Brunswick. It was first named by Carole J. Burrow in 2011 in paleontology, 2011 and the type species is ''Nerepisacanthus denisoni''. Additional specimen is known from Bertie Formation, making that species the oldest near-complete acanthodian. References Ischnacanthiformes Silurian cartilaginous fish of North America Paleozoic life of New Brunswick Bertie Formation Fossil taxa described in 2011 {{Acanthodii-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Diplacanthiformes
Diplacanthiformes (also known as Diplacanthida, Diplacanthoidei, or Diplacanthini) is an order of "acanthodian" stem- chondrichthyans which lived during the Devonian Period. Subtaxa * ''incertae sedis'' ** Genus '' Bryantonchus'' ** Genus '' Culmacanthus'' ** Genus '' Devononchus'' ** Genus '' Striacanthus'' ** Genus '' Tetanopsyrus'' * Family Diplacanthidae Diplacanthiformes (also known as Diplacanthida, Diplacanthoidei, or Diplacanthini) is an order of "acanthodian" stem- chondrichthyans which lived during the Devonian Period The Devonian ( ) is a geologic period and system of the Paleozoic e ... ** Genus '' Diplacanthus'' ** Genus '' Milesacanthus'' ** Genus '' Ptychodictyon'' ** Genus '' Rhadinacanthus'' * Family Gladiobranchidae? ** Genus '' Gladiobranchus'' ** Genus '' Uraniacanthus''? References Prehistoric cartilaginous fish orders Devonian first appearances Devonian extinctions {{Acanthodii-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Gyracanthides
''Gyracanthides'' is an extinct genus of Acanthodii, acanthodian gnathostome, known from Devonian to Mississippian (geology), Early Carboniferous. Description ''Gyracanthides'' is large Acanthodii, 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 Chondrichthyes, chondrichthyans (as currently delimited), and that Acanthodii, acanthodians are paraphyletic. References [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Diplacanthidae
Diplacanthiformes (also known as Diplacanthida, Diplacanthoidei, or Diplacanthini) is an order of "acanthodian" stem- chondrichthyans which lived during the Devonian Period The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding C .... Subtaxa * ''incertae sedis'' ** Genus '' Bryantonchus'' ** Genus '' Culmacanthus'' ** Genus '' Devononchus'' ** Genus '' Striacanthus'' ** Genus '' Tetanopsyrus'' * Family Diplacanthidae ** Genus '' Diplacanthus'' ** Genus '' Milesacanthus'' ** Genus '' Ptychodictyon'' ** Genus '' Rhadinacanthus'' * Family Gladiobranchidae? ** Genus '' Gladiobranchus'' ** Genus '' Uraniacanthus''? References Prehistoric cartilaginous fish orders Devonian first appearances Devonian extinctions {{Acanthodii-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Shark
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the Division (taxonomy), division Selachii and are the sister group to the Batoidea, Batomorphi (Batoidea, rays and skate (fish), skates). Some sources extend the term "shark" as an informal category including Extinction, extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as ''Cladoselache'' and ''Doliodus'' first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Ordovician, Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (Selachii) are known from the Early Jurassic around , with the oldest known member being ''Agaleus'', though records of true shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Silurian
The Silurian ( ) is a geologic period and system spanning 23.5 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 third and shortest period of the Paleozoic Era, and the third of twelve periods of the Phanerozoic Eon. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods ( myriapods, arachnids and hexapods) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Fish Fin
Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only by muscles. Fish fins are distinctive anatomical features with varying structures among different clades: in ray-finned fish (Actinopterygii), fins are mainly composed of bony spines or rays covered by a thin stretch of scaleless skin; in lobe-finned fish ( Sarcopterygii) such as coelacanths and lungfish, fins are short rays based around a muscular central bud supported by jointed bones; in cartilaginous fish ( Chondrichthyes) and jawless fish ( Agnatha), fins are fleshy " flippers" supported by a cartilaginous skeleton. Fins at different locations of the fish body serve different purposes, and are divided into two groups: the midsagittal ''unpaired fins'' and the more laterally located ''paired fins''. Unpaired fins are p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Gyracanthidae
Gyracanthidae is a 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 was originally classified in order Climatiiformes The Climatiiformes is a paraphyletic 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 t ..., later research questioned this. References Prehistoric cartilaginous fish families {{Paleo-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Osteichthyes
Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes (cartilaginous fish) and the extinct placoderms and acanthodians, which have endoskeletons primarily composed of cartilage. The vast majority of extant taxon, extant fish are members of Osteichthyes, being an extremely diverse and abundant group consisting of 45 order (biology), orders, over 435 family (biology), families and 28,000 species. The group is divided into two main clades, the ray-finned fish (Actinopterygii, which makes up the vast majority of extant fish) and the lobe-finned fish (Sarcopterygii, which gave rise to all land vertebrates, i.e. tetrapods). The oldest known fossils of bony fish are about 425 million years old from the late Silurian, which are also transitional fossils showing a dentition, tooth pattern th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
