Ammonites were a type of marine creature. Their remains are often relatively common in rocks of the Jurassic and Cretaceous periods. The only part of the animal commonly found preserved is the coiled shell. This causes many people to think of ammonites as big snails. In fact ammonites were far more complicated creatures related to the present day octopus and squid. They moved by squirting water through a tube called the siphon, a form of jet propulsion.

			The modern Nautilus is related to ammonites and may give an idea of what their soft parts looked like.
			Some adult ammonites have strange projections at the mouth of their shells. It is thought these were involved in mating and only occur on male shells.
			There are many different species of ammonite. They evolved rapidly and only existed for a geologically short period of time. This makes them ideal for dating rock layers
			Cross-sectioned ammonites show many separate chambers. The last chamber contained the animal’s body. All the others held gas. This gave the animal buoyancy.

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