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. The teleosts are a very successful group occupying the reef and open ocean habitats. The lobe-finned fishes bear fleshy extensions on the body. Lungfishes in Australia live in water and gulp air at the surface until the pool dries up, then encase themselves in mud waiting for the next rainy season.