Ammonite body chamber
Many ammonites are only well-preserved as ‘body chambers’. This is the long, last chamber of the shell that housed the soft parts, with the head extending from the end. When these soft parts rotted away, mud was washed inside, preserving that part of the shell. However, the rest of the shell, which consisted of a series of hollow chambers, was not filled with mud and as a result was crushed flat. The body chamber typically takes up the last half whorl of the shell.
Find out more about ammonites on the molluscs pages.