Ammonites are probably the most successful creatures that ever lived on the Earth. They first showed up in the Devonian fossil record nearly 400 Million years ago and are one of the most abundant fossils right through to the Cretaceous age. Ammonite's get their name from the Egyptian god Ammon (AMUN) because it was thought that their coiled shape looks like the Horns of Amun. They are a type of mollusc that were excellent swimmers and were free swimming and lived in the upper levels of the ocean. Ammonites make excellent index fossils, often being able to date rock layers. There were many thousands of species of Ammonites but they almost went extinct during the The Triassic–Jurassic extinction event about 201 million years ago and only the Psiloceratidae family survived - becoming the ancestors of all later Ammonites. Ammonite’s completely died out with the Dinosaurs 66 million years ago and there are no living relatives alive today.