Ammonite – Chambered
Ammonite are a group of cephalopod animals that lived as swimmers in the shallow parts of the ancient oceans. They belonged to a group of predators which includes their living relatives; the octopus, squid, cuttlefish and nautilus.
In appearance, their shells were coiled and smooth. Ammonite developed hollow growth chambers sealed and separated by walls, which allowed them to have buoyancy – the same principal as submarines.
When fossilized, the hollow growth chambers filled with minerals such as calcite and barite, hence their colour. Some ammonite fossils bear intricate patterned details on their outer surface called sutures. When cut and polished, the suture growth lines and chambers are highly visible.
The free swimming marine ammonite is now extinct.