Largest class of vertebrates

There are c. 28,000 species of Osteichthyes, accounting for 96% of all fish species. They form the largest class of vertebrates (animals with backbones). Osteichthyes are bony fish; they have skeletons made of bone. By contrast, Chondrichthyes are cartilaginous fish; they have skeletons made of cartilage, a flexible but firm tissue less stiff than bone.