Acipenseriformes

thumb|Fossil of the Chondrosteidae|chondrosteid Strongylosteus hindenburgi, Tübingen thumb|Fossil of the Peipiaosteidae|peipiaosteid Yanosteus longidorsalis, [[MHNT]] thumb|The living Polyodontidae|polyodontid Polyodon spathula (American paddlefish) thumb|The living Acipenseridae|acipenserid Acipenser ruthenus (sterlet) thumb|The living Acipenseridae|acipenserid [[Pseudoscaphirhynchus kaufmanni (false shovelnose sturgeon)]]

Paddlefish are members of the ray-finned fish family Polyodontidae, which belong to the basal order Acipenseriformes, one of two living groups within this order alongside sturgeons (Acipenseridae). Their most distinctive feature is an elongated rostrum that enhances electroreception, allowing them to detect prey in murky water. Both recent and fossil paddlefish occur exclusively in North America and Eastern Asia.

thumb|left|Fossil of Chondrosteus|Chondrosteus acipenseroides from [[Lyme Regis]] thumb|left|Strongylosteus hindenburgi fossil from [[Posidonia Shale, Staatliches Museum für Naturkunde Stuttgart]]

Chondrosteus ("cartilage bone" in Greek) is a genus of extinct marine actinopterygian (ray-finned fish) belonging to the family Chondrosteidae. It lived during the Hettangian and Sinemurian (early Early Jurassic) in what is now England. Chondrosteus is related to sturgeons and paddlefishes as part of the clade Acipenseriformes, and is one of the earliest known definitive members of the group. 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 like in paddlefish. It is repre

thumb|left|Peipiaosteus pani fossil thumb|left|Peipiaosteus pani fossil thumb|left|Fossil of the Peipiaosteidae|peipiaosteid Yanosteus longidorsalis (at [[MHNT), a close relative of Peipiaosteus]]

REDIRECT Acipenseriformes#Classification

Peipiaosteidae is an extinct family of fish, known from the Late Jurassic and Early Cretaceous of Asia. They are members of Acipenseriformes, related to sturgeons (Acipenseridae) and paddlefish (Polyodontidae). Fossils have been found in freshwater deposits in China, Russia, Kazakhstan, and Mongolia. They are generally considered either the earliest diverging group of Acipenseriformes, or the sister group to the clade containing Acipenseridae and Polyodontidae. At least Yanosteus was likely to have been piscivorous, based on a specimen of Lycoptera found in the mouth of one specimen.

Strongylosteus is an extinct genus of prehistoric ray-finned fish that lived during the early Toarcian age of the Early Jurassic epoch. Its type species is Strongylosteus hindenburgi (monotypy). It is related to modern sturgeon and paddlefish (Acipenseroidei).