there are only eight living species of lobe-finned fish (Sarcopterygii), including the lungfish and coelacanth s. Traditionally, the bony fish had been treated as a class within the vertebrates, with Actinopterygii and Sarcopterygii as subclasses. However, some recent works have elevated Osteichthyes to superclass, with Actinopterygii and Sarcopterygii as classes. Biology