As the Paleozoic drew to a close, placoderms were replaced by cartilaginous and bony fishes. Existing Jawless Fishes Descendants of the early jawless fish are present today in the lampreys and hagfishes. Both have a cylindrical, eel-like body with no paired fins. A notochord and cartilaginous skeleton are present. Lampreys are parasitic on other fish, attaching to them with an oral, suckerlike disk.
Hagfishes are scavengers that look like large worms wit h feelers around the mouth.
They possess a streamlined body with a cartilaginous endoskeleton, gill slits, and fins. This group includes the sharks, skates, rays, and chimaeras. Chimaeras are almost scaleless, with a body resembling a rat. Most bony fishes are ray-finned fishes. The highly maneuverable fins are supported by rays that originate from he dermis.