Chondrostean

chondrostean, (subclass Chondrostei), any of approximately 30 species of primitive ray-finned bony fishes that inhabit marine and freshwater environments of North America and Eurasia. Chondrosteans make up one of the three major subdivisions of the superclass Actinopterygii, the other two being the holosteans and the teleosts. The only living representatives are the sturgeons (family Acipenseridae) and paddlefishes (family Polyodontidae) in the order Acipenseriformes. Some taxonomies also include the bichirs and reedfish of Africa (order Polypteriformes), but this remains a subject of much debate. Many taxonomists argue that the subclass Chondrostei is a paraphyletic group—that is, a taxonomic group that does not include all descendants of a common ancestor.