THE SHELL OF THE AMMONITE

Much like today’s nautilus, the ammonite inhabited a spirally coiled shell, in the foremost part of which the animal lived. Fine growth lines indicate that the ammonite enlarged its shell a little every day. Approximately once a month, the animal slipped forward a little and inserted a new chamber septum towards the back. This newly created, water-filled chamber was then first pumped empty and then filled with water or body fluid as a buoyancy weight as required. If more water was pumped into the chamber, the shell became heavier and the ammonite sank to the bottom. If less liquid was used, the housing became lighter and the ammonite floated up into higher water layers.

In order to be able to fill the individual sections of the chambered part of the housing with gas or liquid accordingly, the chambers were connected to each other via a siphuncle.