Looking at an ammonite, you might think looking at them that the animal that lived in the shell was like a snail, but you would be wrong. In fact ammonites were related to the present-day octopus and squid. In most ammonite fossils we only have the hard shell, but occasionally we get the softer parts of the body and these show that ammonites had tentacles and a tube through which they probably blew water to propel themselves along.
Ammonites vary considerably in size.
Some are the size of a small coin, others are as big as a tyre. You can find some enormous ammonites on the beaches on the Isle of Wight. Part of an ammonite found at Folkestone, Kent. Inside the shell were chambers which would have been full of gas to keep the ammonite upright and bouyant. In the picture you can see the frilly lines of the chambers.