The diversity of the fishes exceeds that of all other vertebrate groups. Within the fishes, the most diverse group is the ____.

A) jawless fishes
B) ray-finned fishes
C) lobe-finned fishes
D) hagfish and lampreys
E) cartilaginous fishes

Ray-finned fishes make up the most diverse group within the fishes, with over 30,000 known species. Jawless fishes and cartilaginous fishes have far fewer species, with only around 100 species of hagfish and lampreys and around 1,200 species of sharks, rays, and chimaeras, respectively. Lobe-finned fishes, while important in the evolution of tetrapods (including humans), are also relatively low in diversity, with only eight living species.