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Pronounced – Am-mon-nite
Meaning of name – The shell resembles the coiled ram’s horn (a ram was the symbol for the Egyptian god Ammon)
Group – Cephalopods, Mollusc
Age – Lower Jurassic, around 195 million years old

Ammonites are a well known fossil and easily recognised by their coiled shell. They first evolved around 240 million years ago and became a very successful group of animals. They died out around the same time as the dinosaurs about 65 million years ago. Ammonites were free swimming creatures related to squid and octopuses. Like these modern relatives they would have been predators, catching prey with their long arms. Their shell was divided up into chambers filled with liquid and gas, which kept them buoyant in the water. They can be preserved in a number of different ways.

Mature Ammonite

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This stunning Arnioceras ammonite has a strange process at the end of the opening of its shell. This is called a lappet and can tell us that this is an adult specimen. Many species of ammonites show differences at this part of the shell and experts think the differences mean they are male or female. This ammonite was found by David Sole and prepared by Andy Cowap. It is now on display at Lyme Regis Museum.

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