• Cephalopods are a group of Mollusks that includes squids, octopuses, cuttlefish, and their relatives.
• Prehistoric cephalopods had a shell, nautilus still has it.
• Other cephalopods reduced it to an internal shell, or lost it completely.
• The ones with shells divide them into chambers full of water and gases for controlling floatability.
• In all cephalopods the mantle forms a tube called the siphon, which they use to pump water out of their body, and propel themselves.
• In cephalopods the ctenidia are inside the body.
• Their mouth looks like a parrot beak. Inside it there is a radula, a tongue full of teeth that they use to rasp their food.
• Their eyes look similar to human or mammalian eyes from outside, but they have a different internal structure.
• The tentacles are located around the mouth. Sometimes they have suckers and/or hooks on them.

Nautilus; photo by Schristia cc-by	Squid; photo by Dan Hershman cc-by	Octopus; photo by BBM explorer cc-by

Sources:

-The Tree of Life - www.tolweb.org:
-The Variety of Life, Colin Tudge, 2000

Citation: García, A.I. 2015. The Tree Of Nature (Online) at http://thetreeofnature.com

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