Ammonites were a group of marine molluscs that also include today's squid. Today these animals have their shell inside, but the Ammonites still had their shell outside the body, just like snails.
The ammonite is approximately 112 million years old and completely fossilized. This copy has been sawed and polished. This makes the different rooms nicely visible.
Fossil ammonite from Madagascar
The most beautiful ammonites are found in Madagascar and can measure up to 25 centimeters in diameter. This ammonite belongs to the Cleoniceras family. Calcite crystals occur in some hollow chambers. These are actually crystal geodes within the fossil. Ammonites, like the dinosaurs, died out about 65 million years ago.