Ammonites

The Ammonites (Ammonoidea) are an extinct subclass of Molluscs of the class Cephalopods with a multi-chamber spiral shell with a diameter from several centimeters to 2 meters. The animal was inhabiting the last camera, and the others were filled with gas and played the role of a floating apparatus. Due to their wide geographic distribution and their rapid evolution, ammonites are leading fossils to establish the geological age of the sediments. Ammonites appear through the Silurian period, reach maximum development through the Mesozoic and disappear at the end of the same era. They bear the name of the Egyptian god Amon because of their spiral shape.