One of the more unusual ammonites from the Blue Lias near Lyme Regis. Ammonites have a spiral shell divided into chambers. It could control its buoyancy in the water by filling the chambers with gas and water. The soft body of the ammonite only took up the last half whorl of the shell. Only the shells of ammonites have ever been found as fossils.
Find out more about ammonites on the molluscs pages.