Only the body chamber (the long open chamber) on this ammonite is well-preserved, thanks to it having been filled with mud. The inner chambered shell is a little crushed. The very fine lines on the shell are growth rings, while the pale, irregular grooves are thought to be borings made by other animals. These were made after the sediment that filled the shell had begun turning to stone.
Find out more about ammonites on the molluscs pages.