The nautilus is the oldest cephalopod.
The most ancient representative of the cephalopod mollusks, the nautilus, lives in the deep sea.
Using unique compartments inside its shell, the nautilus fills them with gas to float or with water to sink. Near the mantle is a muscular, funnel-shaped organ. It acts as a kind of nozzle, directing movement.
The nautilus' shell provides reliable protection from predators and water pressure. Unlike its relatives, it has arms instead of tentacles, which lack suction cups and are used to capture prey.