Nautilidae

A family of ancient, deep-sea cephalopods that include the iconic nautiluses, often dubbed “living fossils” because they’ve barely changed in over 500 million years. While most modern cephalopods—like octopuses, squids, and cuttlefish—have evolved soft bodies and fast-moving, often complex behaviors, nautilids have retained their most defining feature: a hard, coiled external shell. This elegant, chambered shell isn’t just for protection—it plays a critical role in buoyancy control, allowing the animal to float or sink by adjusting the gas and liquid inside its internal compartments. In short, they’re the last of their kind: shelled cephalopods in a world dominated by soft-bodied swimmers.

Members of the Nautilidae family, including the chambered nautilus (Nautilus pompilius) and its relatives in the genera Nautilus and Allonautilus, are found mainly in the tropical Indo-Pacific, living along steep coral reef slopes at depths of 100 to 700 meters (328 – 2,297 ft). Unlike their speedy cousins, nautilids are slow-moving and stealthy, drifting along the ocean floor using jet propulsion and a specialized siphon to gently steer and navigate. They are most active at night, when they rise toward shallower waters to forage, and retreat to deeper zones during the day to avoid predators.

A nautilid’s head emerges from the shell and is ringed with up to 90 slender, sticky tentacles—but unlike other cephalopods, these lack suckers. They use these tentacles to grip food like small crustaceans, fish, and detritus, and then manipulate it into their beak-like jaws. Their eyes are also unique: pinhole-style, without a lens, meaning their vision isn’t sharp—but in the dim, deep waters they inhabit, good smell and touch matter more than sight. And unlike other cephalopods that are short-lived and fast-breeding, nautilids grow slowly, live up to 20 years or more, and lay only a few eggs at a time, making their populations especially vulnerable.