Boreosomus
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''Boreosomus'' (meaning: " boreal body") is an
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
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
Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
marine
ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...
. It was first described from the Arctic island of
Spitsbergen Spitsbergen (; formerly known as West Spitsbergen; Norwegian language, Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipel ...
(
Svalbard Svalbard ( , ), previously known as Spitsbergen or Spitzbergen, is a Norway, Norwegian archipelago that lies at the convergence of the Arctic Ocean with the Atlantic Ocean. North of continental Europe, mainland Europe, it lies about midway be ...
,
Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...
), hence its genus name, but was later also discovered in other parts of the world. The
type species In International_Code_of_Zoological_Nomenclature, 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 spe ...
is ''Boreosomus arcticus'' (= ''Acrolepis arctica'' Woodward, 1912).


Classification

''Boreosomus'' belongs to the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Ptycholepidae (= Boreosomidae/Chungkingichthyidae). Other genera of this family are '' Acrorhabdus'' (
Spitsbergen Spitsbergen (; formerly known as West Spitsbergen; Norwegian language, Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipel ...
), '' Ardoreosomus'' (
Nevada Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...
,
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
), '' Chungkingichthys'' (
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
), '' Ptycholepis'' (global) and '' Yuchoulepis'' (
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
). Some studies recover ''Boreosomus'' as a potential chondrostean.


Description

A characteristic feature of ''Boreosomus'' and other ptycholepids is the
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
, which inserts at the level of the pelvic fins in the middle portion of the body. Most contemporary ray-fins have their dorsal fin in a more posterior position, often opposite to the
anal 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 o ...
. Also typical for ptycholepids are the somewhat rectangular, horizontally arranged suborbital bones. ''Boreosomus gillioti'' could reach a body length of about . Caudal fin was divided. Scales were strong and rectangular.


Fossil record

''Boreosomus'' had a worldwide distribution during the
Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which ...
and is also known from the
Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...
. Fossils of ''Boreosomus'' were found, apart from Spitsbergen (Svalbard), in
Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...
,
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
, China (
Shaanxi Shaanxi is a Provinces of China, province in north Northwestern China. It borders the province-level divisions of Inner Mongolia to the north; Shanxi and Henan to the east; Hubei, Chongqing, and Sichuan to the south; and Gansu and Ningxia to t ...
), Spain (
Catalonia Catalonia is an autonomous community of Spain, designated as a ''nationalities and regions of Spain, nationality'' by its Statute of Autonomy of Catalonia of 2006, Statute of Autonomy. Most of its territory (except the Val d'Aran) is situate ...
), United States (
Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...
), and Canada (
British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
).


Species

* ''Boreosomus arcticus'' ( Woodward, 1912) 'Acrolepis arctica'' Woodward 1912">Acrolepis.html" ;"title="'Acrolepis">'Acrolepis arctica'' Woodward 1912(
type species In International_Code_of_Zoological_Nomenclature, 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 spe ...
) - Early Triassic (Induan) of Svalbard * ''Boreosomus gillioti'' (Priem, 1924) [''Diaphorognathus gillioti'' (Priem 1924); ''Gyrolepis gillioti'' Priem 1924] - Early Triassic (Induan) of Madagascar * ''Boreosomus piveteaui'' Nielsen, 1942 - Earliest Triassic (Induan) of Greenland * ''Boreosomus reuterskioeldi'' Stensiö, 1921 - Early Triassic (Induan) of Svalbard * ''Boreosomus scaber'' Stensiö, 1921 - Early Triassic ( Spathian) of Svalbard Indeterminate species are known from the Early Triassic of Canada (British Columbia) and China (
Guizhou ) , image_skyline = , image_caption = , image_map = Guizhou in China (+all claims hatched).svg , mapsize = 275px , map_alt = Map showing the location of Guizhou Province , map_caption = Map s ...
), as well as the Middle Triassic of
Svalbard Svalbard ( , ), previously known as Spitsbergen or Spitzbergen, is a Norway, Norwegian archipelago that lies at the convergence of the Arctic Ocean with the Atlantic Ocean. North of continental Europe, mainland Europe, it lies about midway be ...
, Spain, and possibly the United States (Arizona). The species ''B. merlei'' is now placed in '' Australosomus''.


See also

*
Prehistoric fish __NOTOC__ Prehistoric fish are early fish that are known only from fossil records. They are the earliest known vertebrates, and include the first and extinct fish that lived through the Cambrian to the Quaternary. The study of prehistoric fish is ...
*
List of prehistoric bony fish This list of prehistoric bony fish is an attempt to create a comprehensive listing of all Genus, genera from the fossil record that have ever been considered to be bony fish (class Osteichthyes), excluding purely vernacular terms. The list includ ...


References

Prehistoric ray-finned fish genera Early Triassic fish Middle Triassic fish Triassic bony fish Fossils of Svalbard Fossils of Greenland Fossils of Madagascar Fossils of China Fossils of British Columbia Triassic fish of North America Triassic fish of Europe Triassic fish of Asia Triassic fish of Africa Induan genus first appearances Olenekian genera Anisian genera Ladinian genus extinctions {{Triassic-fish-stub Fossil taxa described in 1921