''Pteronisculus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of prehistoric

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 h ...

that lived 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 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a ...

and

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma ...

epochs of the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

period. It was first described under the name "''Glaucolepis''" by Erik Stensiö in 1921 and was later shown to be a

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are al ...

of ''Pteronisculus'' described by

Errol White Errol Ivor White CBE FRS FLS FGS (30 June 1901 – 11 January 1985) was a British geologist. He was President of the Ray Society from 1956 to 1959 and President of the Linnean Society of London from 1964 to 1967. He was educated at Highgate Sc ...

in 1933. However, because the name "''Glaucolepis''" is preoccupied (it had already been given to the extant lepidopteran '' Glaucolepis'' Braun, 1917), ''Pteronisculus'' became the valid genus name for the Triassic fish.White, E. I. and Moy-Thomas, J. A. (1940): VII.—Notes on the nomenclature of fossil fishes. Part II. Homonyms D–L: Journal of Natural History 11:98–103

Appearance and distribution

Like many other early ray-finned fishes, ''Pteronisculus'' had a bullet-shaped skull with large eyes near the front end, and a large

gape The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for foo ...

armed with small to large, conical teeth. Its body was covered with small rhombic scales that show peg-and-socket articulation. ''Pteronisculus'' had enlarged

pectoral 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 ...

s and small

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two e ...

s. The

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal co ...

and

anal 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 s ...

s were virtually opposed to each other. The

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 s ...

was

heterocercal 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 ...

. ''Pteronisculus'' had a wide geographic range during the Early Triassic. Fossils were collected in

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

Spitsbergen Spitsbergen (; formerly known as West Spitsbergen; Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipelago in northern N ...

and the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

(possibly also

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost Provinces and territories of Canada, province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

). From the Middle Triassic, it is only known from South China. Its occurrence in 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 Pale ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...

has been questioned. About 13 species have been described to date, ranging from to in length.

Classification

''Pteronisculus'' was originally referred to the

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

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 ...

, but was removed due to differences to ''

Palaeoniscum ''Palaeoniscum'' (from el, παλαιός , 'ancient' and el, ὀνίσκος 'cod-fish' or 'woodlouse') is an extinct genus of ray-finned fish from the Permian period (Guadalupian-Lopingian) of Europe (England, Germany, Czech Republic?, Turk ...

''.Xu et al. (2014): ''Pteronisculus nielseni'' sp. nov., a new stem-actinopteran fish from the Middle Triassic of Luoping, Yunnan Province, China. Vertebrata PalAsiatica 52:364-380 https://www.researchgate.net/profile/Guang-Hui_Xu3/publication/268485382_Pteronisculus_nielseni_sp_nov_a_new_stem-actinopteran_fish_from_the_Middle_Triassic_of_Luoping_Yunnan_Province_China/links/546c702b0cf257ec78ffec6a/Pteronisculus-nielseni-sp-nov-a-new-stem-actinopteran-fish-from-the-Middle-Triassic-of-Luoping-Yunnan-Province-China.pdf Based on similarities with the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

Turseodus ''Turseodus'' is an extinct genus of ray-finned fish found in Late Triassic freshwater sediments of the United States. Two species have been described, ''T. acutus'' from the Lockatong Formation of Pennsylvania, and ''T. dolorensis'' from ...

'', it was provisionally included in Turseoidae.C. Romano, A. López-Arbarello, D. Ware, J. F. Jenks, and W. Brinkmann. 2019. Marine Early Triassic Actinopterygii from the Candelaria Hills (Esmeralda County, Nevada, USA). Journal of Paleontology 93:971-1000 https://doi.org/10.1017/jpa.2019.18 A

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

of ''Pteronisculus'' and ''Turseodus'' is the tooth-bearing lachrymal. However, ''Turseodus'' is incompletely known and a close relationship with ''Pteronisculus'' has not yet been tested with a

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

analysis. In the cladistic analysis by Ren & Xu,Ren, Y. & Xu, G.-H. (2021): A new species of ''Pteronisculus'' from the Middle Triassic (Anisian) of Luoping, Yunnan, China, and phylogenetic relationships of early actinopterygian fishes. Vertebrata PalAsiatica 59:169-199 https://www.researchgate.net/profile/Vertebrata-Palasiatica/publication/353373478_A_new_species_of_Pteronisculus_from_the_Middle_Triassic_Anisian_of_Luoping_Yunnan_China_and_phylogenetic_relationships_of_early_actinopterygian_fishes/links/60f8c5e52bf3553b2902a523/A-new-species-of-Pteronisculus-from-the-Middle-Triassic-Anisian-of-Luoping-Yunnan-China-and-phylogenetic-relationships-of-early-actinopterygian-fishes.pdf ''Pteronisculus'' was recovered in a

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

relationship with the Carboniferous ''

Cyranorhis ''Cyranorhis'' is an extinct genus of prehistoric bony fish that lived during the Serpukhovian age of the Carboniferous period in what is now Montana, United States. Classification Based on the cladistic analysis by Ren & Xu, ''Cyranorhis'' was ...

'', a genus that has been referred to the probably

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

family Rhadinichthyidae.

References

Palaeonisciformes Early Triassic fish Middle Triassic fish Prehistoric animals of China Prehistoric animals of Madagascar {{Triassic-fish-stub

Appearance and distribution

Classification

See also

References