Vertebrates are classified into four major groups based on morphology: cyclostomes (jawless fishes), chondrichthyes (cartilaginous fishes), teleostomes (bony fishes), and tetrapods. Cyclostomes include lampreys and hagfishes; they have no lateral fins, swim using body undulations. The chondrichthyes include sharks, rays, and chimaeras. The teleostome, or osteichthyian, fishes are often divided into ray-finned fishes and lobe-finned fishes. Tetrapods include all limbed vertebrates and include amphibians, reptiles, birds, and mammals.