This has led to an alternative classification, splitting the Osteichthyes into two full classes. Paradoxically, Sarcopterygii is under this scheme considered monophyletic, as it includes the four classes of tetrapods. Most bony fish belong to the ray-finned fish (Actinopterygii); there are only eight living species of lobe-finned fish (Sarcopterygii), including the lungfish and coelacanths.