Cuttlefish are relatives of octopuses, but more closely related to squid. Those three—octopuses, cuttlefish, squid—are all members of a group called the cephalopods. The other well-known cephalopods are nautiluses, deep-sea Pacific shellfish which live quite differently from octopuses and their cousins. Octopuses, cuttlefish, and squid have something else in common: their large and complex nervous systems.
