''Chondrosteus'' is a

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 ...

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 ...

actinopterygian (ray-finned fish) belonging to the family

Chondrosteidae Chondrosteidae is a family (biology), family of extinct marine actinopterygian fishes in the order Acipenseriformes. Three genera are known from the Early Jurassic of Europe, ''Chondrosteus'', ''Gyrosteus'', and ''Strongylosteus''. Included sp ...

. It lived during the

Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and ...

(early

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

) in what is now

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. ''Chondrosteus'' is remotely related to

sturgeons 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 ...

and paddlefishes. Similar to sturgeons, the jaws of ''Chondrosteus'' were free from the rest of the skull (projectile jaw system). Its scale cover was reduced to the upper lobe of 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 se ...

like in paddlefish. The species ''Chondrosteus hindenburgi'' from the

Toarcian The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarcian ...

(late

) of

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

was reallocated to the genus ''

Strongylosteus ''Strongylosteus'' is an extinct genus of prehistoric ray-finned fish that lived during the early Toarcian age of the Early Jurassic epoch.Hennig, E. (1925). ''Chondrosteus Hindenburgi'' Pomp.---Ein «Stör» des württembergischen Ölschiefers ...

''. Although some authors have suggested that the latter might be a junior synonym of ''Chondrosteus'', there are no recent comparative studies on these two genera.

References

External links

* Acipenseriformes Prehistoric ray-finned fish genera Fossils of Great Britain Jurassic fish of Europe Jurassic bony fish {{Jurassic-fish-stub