''Palaeoniscum'' (from el, παλαιός , 'ancient' and el, ὀνίσκος 'cod-fish' or 'woodlouse') is an extinct

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 com ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

from the

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

period (

Guadalupian The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± 0. ...

Lopingian The Lopingian is the uppermost series/last epoch of the Permian. It is the last epoch of the Paleozoic. The Lopingian was preceded by the Guadalupian and followed by the Early Triassic. The Lopingian is often synonymous with the informal terms l ...

) of Europe (England, Germany, Czech Republic?, Turkey), North America (Greenland), and possibly other regions. The genus was named ''Palaeoniscum'' in 1818 by

Henri Marie Ducrotay de Blainville Henri Marie Ducrotay de Blainville (; 12 September 1777 – 1 May 1850) was a French zoologist and anatomist. Life Blainville was born at Arques, near Dieppe. As a young man he went to Paris to study art, but ultimately devoted himself to natur ...

, but was later misspelled as ''Palaeoniscus'' by Blainville and other authors (notably

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he rec ...

). ''Palaeoniscum'' belongs to the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Palaeoniscidae Palaeoniscidae is an extinct family of ray-finned fishes (Actinopterygii) ascribed to the order Palaeonisciformes. The family includes the genus '' Palaeoniscum'' and potentially other Palaeozoic and Mesozoic early actinopterygian genera. The ...

The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

''Palaeoniscum freieslebeni'' was named after

Johann Carl Freiesleben Johann Karl Freiesleben (14 June 1774 – 20 March 1846) was a German mineralogist and mining commissioner in Saxony. He was a childhood friend and correspondent of Alexander von Humboldt and was a promoter of stratigraphy and geognosy as taught by ...

(1774–1846), mining commissioner of

Saxony Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state of ...

. ''P. freieslebeni'' is the most common

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

in the

Wuchiapingian In the geologic timescale, the Wuchiapingian or Wujiapingian (from in the Liangshan area of Hanzhong, Shaanxi Province) is an age or stage of the Permian. It is also the lower or earlier of two subdivisions of the Lopingian Epoch or Series. The ...

aged

Kupferschiefer The Kupferschiefer (German for Copper Shale, also called Copper Slate) or Kupfermergel (Copper Marl), (T1 or Z1) is an extensive and remarkable sedimentary unit in Central Europe. The relatively monotonous succession is typically and maximum th ...

and

Marl Slate The Marl Slate Formation is a geological formation in England. Despite its name, it is mostly dolomite rock. The Marl Slate Formation was formed about 273 to 259 million years ago, during the Guadalupian and Lopingian epochs of the late Permian ...

, where it constitutes 80% of all fish fossils. ''Palaeoniscum'' had a

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...

-shaped body in length, with a deeply forked

caudal 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 se ...

and tall

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

, indicating that it was a fast swimmer. It was probably an active predator, feeding on other freshwater fish. Its sharp

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

could be replaced when lost, a trait also seen in modern

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

s. Like other early ray-finned fish, ''Palaeoniscum'' had air sacs connected to the mouth, which served as a primitive

swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled Organ (anatomy), organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their curren ...

. Several

Palaeozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and '' ...

and

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

species that have been ascribed to the genus ''Palaeoniscum'' were later shown to be only distantly related with ''P. freieslebeni''. These species were subsequently removed and transferred to other genera (e.g., '' Acentrophorus'', '' Aeduella'', ''

Paramblypterus ''Paramblypterus'' is an extinct genus of bony fish. This taxon would often fall under predation from Paleozoic tetrapods such as ''Sclerocephalus'' See also * Prehistoric fish * List of prehistoric bony fish A ''list'' is any set of item ...

'', see list below). The allocation of other species to ''Palaeoniscum'' (see list below) is often doubtful and mostly based on superficial resemblance with ''P. freieslebeni''. ''Palaeoniscum'' is the name giving taxon of the

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

Palaeonisciformes The Palaeonisciformes (Palaeoniscida) are an extinct order of early ray-finned fishes ( Actinopterygii). Palaeonisciformes ''sensu lato'' first appeared in the fossil record in the Late Silurian and last appeared in the Late Cretaceous. The na ...

(or Palaeoniscoidei), a

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...

group comprising several superficially similar looking but not closely related early

actinopterygian Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or ho ...

taxa. Palaeonisciformes is considered a

wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...

by modern taxonomic standards.

Species

* ''Palaeoniscum angustum'' (Rzehak, 1881) 'Palaeoniscas angustus'' Rzehak, 1881* ''Palaeoniscum antipodeum'' (Egerton, 1864) 'Palaeoniscus antipodeus'' Egerton, 1864* ''Palaeoniscum antiquum'' Williams, 1886 * ''Palaeoniscum arenaceum'' Berger, 1832 * ''Palaeoniscum capense'' (Bloom, 1913) 'Palaeoniscus capensis'' Bloom, 1913* ''Palaeoniscum comtum'' (Agassiz, 1833) 'Palaeoniscus comtus'' Agassiz, 1833* ''Palaeoniscum crassum'' (Woodward, 1908) 'Palaeoniscus crassus'' Woodward, 1908* ''Palaeoniscum daedalium'' Yankevich & Minich, 1998 * ''Palaeoniscum devonicum'' Clarke, 1885 * ''Palaeoniscum elegans'' (Sedgwick, 1829) 'Palaeoniscus elegans'' Sedgwick, 1829* ''Palaeoniscum freieslebeni'' de Blainville, 1818 (

) [''Eupalaeoniscus freieslebeni'' (de Brainville, 1818); ''Palaeoniscus freieslebeni'' (de Brainville, 1818); ''Palaeoniscus macropomus'' Agassiz, 1833; ''Palaeoniscus magnus'' Woodward, 1937] * ''Palaeoniscum hassiae'' (Jaekel, 1898) [''Galeocerdo contortus hassiae'' Jaekel, 1898; ''Palaeomyzon hassiae'' (Jaekel, 1898)] * ''Palaeoniscum kasanense'' Geinitz & Vetter, 1880 * ''Palaeoniscum katholitzkianum'' (Rzehak, 1881) 'Palaeoniscas katholitzkianus'' Rzehak, 1881* ''Palaeoniscum landrioti'' (le Sauvage, 1890) 'Palaeoniscus landrioti'' le Sauvage, 1890* ''Palaeoniscum longissimum'' (Agassiz, 1833) 'Palaeoniscus longissimus'' Agassiz, 1833* ''Palaeoniscum macrophthalmum'' (McCoy, 1855) 'Palaeoniscus macrophthalmus'' McCoy, 1855* ''Palaeoniscum moravicum'' (Rzehak, 1881) 'Palaeoniscas moravicus'' Rzehak, 1881* ''Palaeoniscum promtus'' (Rzehak, 1881) 'Palaeoniscas promtus'' Rzehak, 1881* ''Palaeoniscum reticulatum'' Williams, 1886 * ''Palaeoniscum scutigerum'' Newberry, 1868 * ''Palaeoniscum vratislavensis'' (Agassiz, 1833) 'Palaeoniscus vratislavensis'' Agassiz, 1833

Species moved to other genera

* ''Palaeoniscum abbsi'' Kirkby, 1862 → †'' Acentrophorus varians'' (Kirkby, 1862) * ''Palaeoniscum blainvillei'' (Agassiz, 1833) 'Palaeoniscus blainvillei'' Agassiz, 1833→ †'' Aeduella blainvillei'' (Agassiz, 1833) * ''Palaeoniscum gelberti'' Goldfuss, 1847 → †'' Paramblypterus duvernoyi'' (Agassiz, 1833)

References

Prehistoric ray-finned fish genera Permian bony fish Palaeonisciformes Permian fish of Europe Permian fish of North America Fossil taxa described in 1818 {{Palaeonisciformes-stub