Acipenseriformes

Acipenseriformes; Temporal range:
	Atlantic sturgeon; (Acipenser oxyrhynchus)
	American paddlefish; (Polyodon spathula)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Subclass:	Chondrostei
Order:	Acipenseriformes; L. S. Berg, 1940
Subgroups
	Genus †Eochondrosteus?; Family †Chondrosteidae (sometimes placed in its own order); Family †Peipiaosteidae; Suborder Acipenseroidei Family Acipenseridae (sturgeon); Family Polyodontidae (paddlefish); ;

Fossil of the †chondrosteid †*Strongylosteus hindenburgi*, Tübingen

Fossil of the †peipiaosteid †*Yanosteus longidorsalis*, MHNT

The living polyodontid *Polyodon spathula* (American paddlefish)

The recent polyodontid *Psephurus gladius* (Chinese paddlefish)

The living acipenserid *Acipenser ruthenus* (sterlet)

The living acipenserid *Pseudoscaphirhynchus kaufmanni* (false shovelnose sturgeon)

The living acipenserid *Acipenser oxyrinchus* (Atlantic sturgeon)

The living acipenserid *Scaphirhynchus platorynchus* (Shovelnose sturgeon)

Acipenseriformes /æsɪˈpɛnsərɪfɔːrmiːz/ is an order of basal ray-finned fishes that includes living and fossil sturgeons and paddlefishes (Acipenseroidei), as well as the extinct families Chondrosteidae and Peipiaosteidae. They are the second earliest diverging group of living ray-finned fish after the bichirs. Despite being early diverging, they are highly derived (modified from their ancestors), having only weakly ossified skeletons that are mostly made of cartilage, and in modern representatives highly modified skulls.