The cephalopods are the mollusk class Cephalopoda characterized by bilateral body symmetry, a prominent head, and a modification of the mollusk foot, a muscular hydrostat, into the form of arms or tentacles. Teuthology is the study of cephalopods. The class contains two main subclasses. In the Coleoidea, the mollusk shell has been internalized or is absent; this subclass includes the octopuses, squids, and cuttlefish. In the Nautiloidea the shell remains; this subclass includes the nautilus. There are around 786 distinct living species of Cephalopods.
Mini Lesson: How Smart is the Octopus? Cephalopods are found in all the oceans of the world and at all depths. None of them can tolerate freshwater, but a few species do tolerate more or less brackish water.
Diagram Created By: Adrienne L
Date Published: 10/08
Photo Credit: http://www.royalbcmuseum.bc.ca/programs/expert/octopus/