Ammonites are a group of extinct octupuses that had an extrnal shell of calcite. As the animal grew, its shell divided into body-chambers and a series of gas-filled chambers, which enabled buoyancy in water masses.

Thousands of different species of ammonites have existed for several hundred millions of years. Their size ranged from 1 cm to 2.5 meters in diameter. Many species have been found worldwide, it is assumed that they swam about in open water, perhaps transported by ocean currents. In Norway, ammonites have lived on the continental shelf, Svalbard and Andøya.

Ammonites died out about 65 million years ago.