Cephalopods (Octopus, Squid, Nautilus, Cuttlefish)

This group gathers Mollusks subcategory members belonging to the class Cephalopoda, widely regarded as the most behaviorally and neurologically sophisticated invertebrates known, with a nervous system, problem-solving ability and capacity for rapid learning that rival or exceed many vertebrates. It spans octopuses, soft-bodied and entirely shell-less as adults, capable of squeezing through any gap wider than their beak and of near-instantaneous camouflage by changing both the color and the texture of their skin, squid, fast-swimming hunters that propel themselves by jet propulsion, cuttlefish, renowned even among cephalopods for exceptionally fine control over skin color and pattern used in both camouflage and courtship display, and the chambered nautilus, the only member of this group to retain an external coiled shell, a living link to cephalopod ancestors that were once far more numerous and diverse than their soft-bodied modern relatives. Every species here is an active predator, and most have relatively short lifespans, often only one to two years, compensated for by rapid growth and prolific reproduction.