''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 nom ...

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 un ...

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 and ...

epochs In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

of the

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

. It was first described under the name "''Glaucolepis''" by

Erik Stensiö Prof Erik Helge Osvald Stensiö HFRSE (2 October 1891 – 11 January 1984) was a Swedish paleozoologist. He later took his new surname from his place of origin and is occasionally referred to with both names (as Erik Andersson Stensiö, Erik ...

in 1921 and was later shown to be a synonym of ''Pteronisculus'' described by Errol White in 1933. However, because the name "''Glaucolepis''" is preoccupied (it had already been given to the extant

lepidopteran Lepidoptera ( ) is an order of insects that includes butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 percent of the total described specie ...

'' 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 food ...

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 fins. 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 c ...

and anal fins 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 ...

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 s ...

. ''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 i ...

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 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 states, a federal district, five major unincorporated territori ...

(possibly also

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

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 tot ...

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

Permian The Permian ( ) is a geologic period and System (stratigraphy), 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 ...

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

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''.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 of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. ...

'' Turseodus'', 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 char ...

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 relationship with the Carboniferous '' Cyranorhis'', a genus that has been referred to the probably paraphyletic 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