Class cephalopoda includes squid, octupuses, cuttlefish, shelled nautilus and now extinct ammonites, nautiloids, and bellemnites. Besides octupuses, all members have some sort of external or internal shell which are typically well preserved in the fossil record. Cephalopods are active marine predators, using their tentacles and beak to capture prey.
J. R. Hendricks. 2018. Cephalopoda. In: The Digital Encyclopedia of Ancient Life.