Living around 400 to 65 million years ago and at the same time as the dinosaurs, ammonites were free swimming moluscs of the ancient oceans. They disappeared like the dinosaurs during the same extinction event some 65 million years ago. The animal lived in the last chain of the spiral chambers and filled other chambers with fluid allowing it to sink to avoid predators. This example is particularly large measuring some 19" by 15". making it a central specimen in any collection.