Which phylum contains the class Cephalopoda?

• A. Chordata
• B. Arthropoda
• C. Mollusca
• D. Echinodermata

Answer: (C)

Cephalopods are mollusks, a group that also includes snails, clams, and chitons. In cephalopods the body plan features a mantle that encloses the organs and a foot that has evolved into arms and tentacles around the mouth, sometimes with a siphon for jet propulsion. This combination of a mantle, visceral mass, and a foot adapted for grasping and locomotion is characteristic of Mollusca, placing cephalopods in that phylum.

They differ from other major animal groups in ways that are easy to spot taxonomically: chordates have a notochord and dorsal nerve cord, arthropods have segmented bodies with an exoskeleton, and echinoderms show radial symmetry and a unique water vascular system.