Ammonites were a group of hugely successful aquatic molluscs that looked like the still extant Nautilus, a coiled shellfish that lives off the southern coast of Asia.While the Nautilus lived on, ammonites graced our waters from around 400 million years ago until the end of the Cretaceous, 65 million years. Varying in size from millimeters to meters across, ammonites are prized as both works of art and index fossils helping us date rock.
