Acipenseriformes

Chondrosteus ( = Strongylosteus ) hindenburgi from the Lower Jurassic of wood grubs in the Stuttgart Natural History Museum

The order Sturgeons ( Acipenseriformes ) or " cartilage melting scaler " includes two still existing ( recent ) families of bony fish with 30 species and several fossil groups. They are the only extant representative of the Knorpelganoiden, one depending on the definition, more or less in stride original bone fish. When fossils are Sturgeons since the Jurassic, known possibly even since the Permian.

The sturgeon species have an incompletely ossified skeleton and the scales of the hull are heavily or completely reduced. An important feature is also the reduction of dermal bone of the maxilla maxilla and premaxilla and the hyostyle and thus highly movable suspension of Palatoquadratums, the cartilaginous preformed " Ur - skeleton " of the upper jaw and palate. These transformations are related to a strong ground -based diet of the animals.

All extant species are endangered in their collections, and at least locally extinct. For the protection of these species, in particular the World Sturgeon Conservation Society uses. Some are of great economic importance as a food fish and especially as caviar suppliers.

Phylogeny, systematics and oldest representative

The Acipenseriformes represent a very early branch of the line, the teleosts leads to the modern bony fishes. Your next fossil relatives are the Birgeriidae, a group that is traditionally the " Palaeonisciformes " attributed. The latter are seen as representatives of the first major radiation of bony fish in the Late Paleozoic.

Acipenseriformes are fossil proven safe since the Lower Jurassic. The type Chondrosteus acipenseroides from the Sinemurian and Hettangian of Southwest and Central England is one of the historically oldest known fossil sturgeon species. Another early Jurassic type, Strongylosteus hindenburgi from the Posidonia Shale ( Toarcian ) of wood grubs in Baden- Württemberg possibly also belongs to the genus Chondrosteus.

In 2005, a fossil was described from China, which could extend the stratigraphic range of the sturgeon species even into the Late Permian into it. The representative named Euchondrosteus sinensis comes from the Fangshankou formation of Gansu Province.

A recently live from the sturgeon species, only two families, the sturgeon ( Acipenseridae ) with 24 species in four genera and the paddlefish ( Polyodontidae ) with 2 species in two genera.

The systematics of Acipenseriformes is given in the following list:

• Sturgeons ( Acipenseriformes ): Peipiaosteidae † Peipiaosteus †
• Stichopterus †
• Yanosteus †

• Chondrosteidae † Chondrosteus † = (?) Strongylosteus †
• Gyrosteus †

• True Sturgeons ( Acipenseridae ) House behaved ( Husinae ) Hausen ( Huso ), tart 2 styles

• Acipenser, tart 18 species
• Shovel sturgeon ( Scaphirhynchini ) Scaphirhynchus, tart 3 species in North America
• Pseudoscaphirhynchus, tart 3 types
• Protoscaphirhynchus †

• Protosephurus †
• Palaeosephurinae † Palaeosephurini † Palaeosephurus †

• Polyodontini Paddlefish ( Polydon ) tart 1 type
• Crossopholis †

• Schwertstör ( Psephurus ) tart 1 type