What is an ammonite?

Ammonites were members of the same class of animals as the modern octopus and squid. They were tentacle animals that lived in a flat coiled shell. There were many thousands of different types of ammonite. The shells of some ammonites were as much as 1 m across, but most were much smaller. The animal lived in a small horny cell, constructing a new cell as it grew. The cells contained gas, probably making the shell buoyant and allowing the animal to swim freely. Later, the shells of some ammonites became partly straightened out. Ammonite shells have been well fossilized. They are commonly found on beaches, where they have been washed out of the soft rock by wave action.

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