Ammonite section

Ammonites are extinct cephalopod molluscs generally protected by a flat spiral-shaped shell. Unlike the shell of gastropods, this is divided into several chambers, the last of which is wider and inhabited by the mollusc body. The inner chambers, variously filled with gas, have a hydrostatic function allowing these marine organisms to change their floating depth. Chambers are separated by a number of partitions which are connected to the shell wall, creating several wrinkles on its outer surface; the shape of the shell and appearance of the suture lines are key elements in the classification of the different species of ammonites.