Belemnites are an extinct group of cephalopod that probably looked like a squid.
Unlike nautiloids and ammonites, belemnites had a very solid internal skeleton called a rostrum. Many people will be familiar with belemnite rostra, they are straight, and look rather like bullets.
Apart from their shells, palaeontologists have also found some belemnite fossils that show their internal structure and soft parts. These fossils tell us a great deal about the way these animals lived. Belemnites had large eyes, and swam quickly using a form of jet propulsion. Like the octopus they could probably squirt clouds of black ink at their enemies to avoid attack.