Chondrostei is a group of non-

neopterygian Neopterygii (from Greek νέος ''neos'' 'new' and πτέρυξ ''pteryx'' 'fin') is a subclass of ray-finned fish (Actinopterygii). Neopterygii includes the Holostei and the Teleostei, of which the latter comprise the vast majority of extan ...

ray-finned fish, while the term originally referred to a

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 ...

group of all non-neopterygian ray-finned fish, it was redefined by Patterson in 1982 to be a clade comprising the Acipenseriformes (which includes

sturgeon Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretace ...

and paddlefish) and their extinct relatives. Taxa commonly suggested to represent relatives of the Acipenseriformes include the Triassic marine fish ''

Birgeria ''Birgeria'' is a genus of carnivorous marine ray-finned fish from the Triassic period. ''Birgeria'' had a global distribution. Fossils were found in Madagascar, Spitsbergen, Germany, Switzerland, Italy, Slovenia, China, Russia, Canada and N ...

'' and the Saurichthyiformes, but their the relationship with the Acipenseriformes has been strongly challenged on

cladistical 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 cha ...

grounds.

Coccolepididae Coccolepididae is an extinct family of ray-finned fish, known from the Early Jurassic to Early Cretaceous, most of which were originally referred to the type genus ''Coccolepis.'' They had a widespread distribution, being found in North and South ...

, a group of small weakly ossified Jurassic and Cretaceous fish found in both marine and freshwater environments, have been suggested to be close relatives of the Acipenseriformes, however, this has never been subject to cladistical analysis.

Classification

* Acipenseriformes **

Acipenseridae Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early ...

— sturgeons **

Polyodontidae Paddlefish (family Polyodontidae) are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae). They are distinguished from other fish by their titular elongla ...

— paddlefishes ** Chondrosteidae(†) ** Errolichthyidae(†) *

Cheirolepidiformes ''Cheirolepis'' (from el, χείρ , 'hand' and el, λεπίς 'scale') is an extinct genus of ray-finned fish that lived in the Devonian period of Europe and North America. It is the only genus yet known within the family Cheirolepidae and t ...

(†) *

Guildayichthyiformes Guildayichthyidae is a prehistoric family of marine fish from the Mississippian Bear Gulch Limestone of Montana. It is the only family in the order Guildayichthyiformes. Guildayichthyids possess an uncommon mixture of primitive and modern charac ...

(†) *

Luganoiiformes ''Luganoia'' is an extinct genus of prehistoric bony fish that lived during the early Ladinian stage of the Middle Triassic epoch. See also * Prehistoric fish * List of prehistoric bony fish A ''list'' is any set of items in a row. List or lis ...

(†) *

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 nam ...

(†) ** Acrolepidae(†) **

Birgeriidae ''Birgeria'' is a genus of carnivorous marine ray-finned fish from the Triassic period. ''Birgeria'' had a global distribution. Fossils were found in Madagascar, Spitsbergen, Germany, Switzerland, Italy, Slovenia, China, Russia, Canada and N ...

(†) ** Palaeoniscidae(†) *

Perleidiformes Perleidiformes are an extinct order of prehistoric ray-finned fish from the Triassic period Although numerous Triassic taxa have been referred to Perleidiformes, which ones should be included for it to form a monophyletic group is a matter of on ...

(†) * Phanerorhynchiformes(†) *

Pholidopleuriformes Pholidopleuriformes is an extinct order of ray-finned fish. Classification ** Family †Pholidopleuridae Abel 1919/Wade 1932 *** Genus †'' Gracilignathichthys'' Bürgin 1992 **** †'' Gracilignathichthys microlepis'' Bürgin 1992 *** Genus � ...

(†) *Polypteriformes ** Polypteridae - bichirs and reedfish *

Ptycholepiformes Ptycholepiformes are an extinct order of prehistoric ray-finned fish that existed during the Triassic period and the Early Jurassic epoch. The order includes the genera '' Acrorhabdus'', ''Ardoreosomus'', ''Boreosomus'', '' Chungkingichthys'', ...

(†) * Saurichthyiformes(†) *

Tarrasiiformes Tarasiiformes is an extinct order of prehistoric ray-finned fish. Taxonomy * Order †Tarrasiiformes sensu Lund & Poplin 2002 aplistiaref name="mikko"> ** Family †Tarrasiidae Traquair 1881 emend. Woodward 1891 *** Genus †'' Apholidotos'' ...

(†)

References

{{Taxonbar, from=Q275646 Extant Silurian first appearances Paraphyletic groups