Chondrostei (chondrostean fish) Group of bony fish belonging to the subclass Actinopterygii. Often ranked as a super-order, the chondrosteans have a partly cartilaginous skeleton (see CARTILAGE), a heterocercal tail, a spiracle, and an intestinal spiral valve. The group includes the extant orders Acipenseriformes and Polypteriformes, and the extinct order Palaeonisciformes (palaeoniscids, or ‘ancient fish’).

Chondrostei A group of bony fish belonging to the subclass Actinopterygii. Often ranked as a superorder, the chondrosteans have a partly cartilaginous skeleton, a heterocercal tail, a spiracle, and an intestinal spiral valve. Apart from a number of fossil orders, it includes the extant order Acipenseriformes.