Cephalopoda, a class containing octopus and squid, belongs to which phylum?

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

Answer: (C)

Cephalopods belong to the phylum Mollusca. The defining traits here are a soft body with a mantle and a muscular foot that, in cephalopods, has been modified into arms and tentacles. These features, along with other molluscan characteristics such as a mantle cavity and, in many species, a shell, link cephalopods to snails and clams. This sets them apart from chordates (which have a dorsal nerve cord and notochord), arthropods (segmented bodies with an exoskeleton), and echinoderms (radial symmetry and a water vascular system). The combination of a mantle and a foot adapted for grasping places cephalopods squarely in Mollusca.