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Chondrichthyian
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, except in Holocep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
Myliobatiformes
Myliobatiformes (), commonly known as stingrays, are one of the four orders of batoids, cartilaginous fishes related to sharks. They are members of the subclass elasmobranchs. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown the myliobatiformes to be a monophyletic group, and its more derived members evolved their highly flattened shapes independently of the skates. Characteristics Myliobatiformes share physical characteristics of a long, thin tail with serrated spines and a pancake-like body. They share many characteristics with the batoid order Rajiformes, in which they were previously included. The key difference of the orders is the Myliobatiformes' single-lobed pelvic fin, lack of a mid-tail spine, and general lack of a dorsal fin. Myliobatiformes also possess stinging spines along the tail's base, and generally possess large pectoral fins that are completely fused (except Myliobatidae) to the head. They can camoufla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psammodontiformes
Psammodontidae is an extinct family of holocephalans (sometimes referred to as bradyodonts) known from the Carboniferous and Permian periods. It is the only family of the order Psammodontiformes. The order and family are named for the type genus, '' Psammodus'', and all members are believed to have been durophagous Durophagy is the eating behavior of animals that consume hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil t ... nektobenthic carnivores. The only described remains assigned to Psammodontidae are isolated tooth plates. References Holocephali Prehistoric cartilaginous fish families {{Paleo-holocephalan-stub Carboniferous first appearances Permian extinctions Carboniferous cartilaginous fish Permian cartilaginous fish Carboniferous fish of North America ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plesioselachus
''Plesioselachus'' is an extinct genus of Late Devonian (Famennian) cartilaginous fish with uncertain classification, which contains only one species, ''P. macracanthus'' from the Waterloo Farm lagerstätte in South Africa. Known from a single incomplete articulated skeleton and some isolated remains, it is characterized by having a long dorsal spine with length about one third of body length. Description ''Plesioselachus'' was originally classified as elasmobranch, however a redescription placed it under Chondrichthyes since it lacks sufficient data to consider what subgroup it belongs to. The holotype specimen, which has a preserved length of shows most of postcranial elements while lacking most of the head. It is originally considered that preserved lower jaw ( Meckel’s cartilage) and upper jaw ( palatoquadrate), however these materials are more likely to belong to ceratohyal and hyomandibula. The vertebral column is fully preserved, and extends for toward the caudal fin. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanocetorhinus
''Nanocetorhinus'' is an extinct genus of sharks in the subclass Neoselachii from the Late Oligocene to Middle Miocene. The type species ''N. tuberculatus'' lived across the Northern Hemisphere during the Early to Middle Miocene, and the second species ''N. zeitlingeri'' lived in Austria during the Late Oligocene. Discovery and naming ''Nanocetorhinus tuberculatus'' was described by Underwood and Schlogl in 2013, from 28 partial and complete fossilized teeth (holotype: Z 27485) discovered in the Laksarska Nova Ves Formation at Cerová-Lieskové, Vienna Basin, in Slovakia. It was placed ''incertae sedis'' into the chondrichthyan subclass Neoselachii. The authors expressed an uncertainty with regards to the validity of ''Nanocetorhinus'' being assigned to this subclass, as the teeth from which it was described bore minimal resemblance to those of previously known neoselachian taxa. They also noted other fossils from western Canada and France may represent this species. In 2017, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mcmurdodontidae
''Mcmurdodus'' is an extinct genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ... of chondrichthyan belonging to the family (biology), family Mcmurdodontidae. It contains one species, ''Mcmurdodus featherensis'', from the Middle Devonian of Antarctica. The Australian species ''M. whitei'' was previously included in the genus too, but was moved to a new genus, ''Maiseyodus'', in 2021. Their teeth closely resemble those of modern sharks in the families Cow shark, Hexanchidae and Echinorhinus, Echinorhinidae, and they were tentatively classified in the Hexanchiformes when first described. However, more recent analyses indicate that they lack multiple layers of enameloid on their tooth crowns, something present in all modern sharks and many sharks that coexisted with ''Mcmurdodus' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Listracanthidae
Listracanthidae is a proposed family of extinct cartilaginous fish. It currently includes the genera '' Listracanthus'' and '' Acanthorhachis''. This clade is likely included within Elasmobranchii, but its placement within it is uncertain. Both genera are known from their distinctive spiny dermal dentictles which coat the exterior of their long, slender bodies. They are known from the Viséan to the Early Triassic, mainly from what is now the northern hemisphere. However, there is a possible occurrence in Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl .... References Prehistoric cartilaginous fish families Mississippian first appearances Early Triassic extinctions {{Paleo-cartilaginous-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delphyodontos
''Delphyodontos dacriformes'' is a prehistoric holocephalan fish from the middle Carboniferous-aged Bear Gulch Limestone Lagerstätte, during the Bashkirian Stage in Montana. The adult form is unknown, as the only fossil specimens are of aborted fetuses or recently born young.Lund, R. 1980. Viviparity and intrauterine feeding in a new holocephalan fish from the Lower Carboniferous of Montana. Science, 209: 697‑699. Sharp teeth and fecal matter in the fossils suggests that ''Delphyodontos'' practiced intrauterine cannibalism, like some modern sharks, such as sand tiger shark The sand tiger shark (''Carcharias taurus''), grey/gray nurse shark (in Australia), spotted ragged-tooth shark (in South Africa), or blue-nurse sand tiger, is a species of shark that inhabits subtropical and temperate waters worldwide. It inhabit ...s. Appearance According to the fossils, the recently born would have resembled tadpoles with small, but sharp beaks. Because of the evidence suggesting int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandringa
''Bandringa'' is an extinct genus of elasmobranch known from the Pennsylvanian subperiod of the Carboniferous period. There is currently a single known species, ''B. rayi'', which constitutes the sole member of the monotypic family Bandringidae. The genus was described in 1969 by paleontologist Rainer Zangerl, and is known from exceptionally preserved individuals found in the Mazon Creek Lagerstätte of Illinois.R. Zangerl. (1969). ''Bandringa rayi'': A New Ctenacanthoid Shark form the Pennsylvanian Essex Fauna of Illinois. ''Fieldiana Geology'' 12:157-169 Discovery and naming The holotype specimen, FMNH PF 5686, is a juvenile individual which was found in an ironstone concretion in Illinois during the summer of 1967. This specimen was found by Ray Bandringa, to whom the genus and species owe their name. By 1979, two species from this genus were described, ''B. rayi'' and ''B. herdinae'', but the differences between the two were found to be taphonomic in origin. All Mazon Cre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Incertae Sedis
or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty at specific taxonomic levels is indicated by (of uncertain family), (of uncertain suborder), (of uncertain order) and similar terms. Examples * The fossil plant ''Paradinandra, Paradinandra suecica'' could not be assigned to any family, but was placed ''incertae sedis'' within the order Ericales when described in 2001. * The fossil ''Gluteus minimus (fossil), Gluteus minimus'', described in 1975, could not be assigned to any known animal phylum. The genus is therefore ''incertae sedis'' within the kingdom Animalia. * While it was unclear to which order the New World vultures (family Cathartidae) should be assigned, they were placed in Aves ''incertae sedis''. It was later agreed to place them in a separate order, Cathartiformes. * Boc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocephalimorpha
Holocephali (Sometimes spelled Holocephala; Greek for "complete head" in reference to the fusion of upper jaw with the rest of the skull) is a subclass of cartilaginous fish. While the only living holocephalans are three families within a single order which together are commonly known as chimaeras, the group includes many extinct orders and was far more diverse during the Paleozoic and Mesozoic eras. The earliest known fossils of holocephalans date to the Middle Devonian period, and the group likely reached its peak diversity during the following Carboniferous period. Molecular clock studies suggest that the subclass diverged from its closest relatives, elasmobranchs such as sharks and rays, during the Early Devonian or Silurian period. Extinct holocephalans are typically divided into a number of orders, although the interrelationships of these groups are poorly understood. Several different definitions of Holocephali exist, with the group sometimes considered a less inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
