Cephalopods are the most highly evolved of all molluscs.
Cephalopods use a strong beak to eat other animals that they catch with their tentacles . Early in their evolutionary history, the cephalopods were able to develop an effective means of buoyancy, a chambered shell , allowing them to colonize the water column , with its rich food resources of actively moving large-sized prey. Other than fish, they are the most accomplished swimmers in the sea. The shell is divided into internal gas-filled chambers by septa . The animal lives in the last chamber, the body chamber , and moves forward each time a new septum is secreted.