This sectioned and polished ammonite shows lovely internal structure. Ammonites have a spiral shell divided into chambers. They could control their 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.
This specimen came from the collection of James Harrison, who discovered the dinosaur Scelidosaurus Harrisoni.
Find out more about ammonites on the molluscs pages.