[GASTROPODA] [PELECYPODA] [POLYPLACOPHORA] [SCAPHOPODA] [CEPHALOPODA]
CEPHALOPODA
Squids, cuttlefish and octopuses are members of this class. All species are marine dwellers. These active hunters of the mid-waters and crevice-ridden shores represent specialization for rapid movement and efficient hunting. Modification of the head has resulted in tentacles equipped with suckers. Development of a jet-propulsion system from the foot and mantle cavity, reduction of the shell first to an internal fragment and then its subsequent loss in the octopods, development of vision that is as acute as ours, extremely high intelligence, and possession of a powerful beak and radula for tearing food are basic characteristics of cephalopods. Swift movement and sharp senses substitute for a protective shell. Cephalopods are extremely active and conspicuous, and play an important role in ocean ecology.
There are perhaps less than 1,000 kinds of living cephalopods, although more than 10,000 fossil species have been named. Although most are small in size, the giant squid, Architeuthis, reaches 60 feet in length, including tentacles, while the arm span of a large Octopus hongkongensis can reach over 32 feet. Living shelled cephalopods are relatively small, up to 10 inches in diameter. In the past, however, there were giant shelled nautiloids. The Ordovician Cameroceras had a shell nearly 39 feet long, and the Cretaceous Pachydiscus coilid shell had a diameter of about 9 1/2 feet!
[GASTROPODA] [PELECYPODA] [POLYPLACOPHORA] [SCAPHOPODA] [CEPHALOPODA]