How are chondrosteans related to ray-finned fishes?

Chondrosteans are considered the most primitive members of the ray-finned fishes, a superclass known as Actinopterygii. They represent one of the three major subdivisions of this group, alongside holosteans and teleosts.12

The relationship between these groups is complex, as many taxonomists classify the subclass Chondrostei as a paraphyletic group, meaning it does not include all descendants of a common ancestor. While chondrosteans were once more diverse, they declined during the Mesozoic Era as more advanced actinopterygians—specifically the ancestors of holosteans and teleosts—arose from palaeoniscid-like ancestors.132

Modern chondrosteans, such as sturgeons and paddlefishes, are genealogically distinct from other ray-finned lineages. In fact, some research suggests that these living acipenseriforms are more closely related to holosteans than they are to other groups sometimes placed within the chondrostean subclass, such as bichirs. Consequently, the classification of these fishes remains a subject of ongoing scientific debate.31