Ammonites are an extinct group of mollusks. They evolved at the beginning of the Devonian Period (almost 400 million years ago). Ammonites died out about the same time as the dinosaurs at the end of the Cretaceous Period, 65 million years ago.
These ancient shellfish are both geologically fascinating and aesthetically pleasing. They were originally called Ammon’s stones due to their resemblance to the ram’s horns of Ammon, the Egyptian god of life and procreation. They have been collected and prized for centuries. Ammonites are a relative to the modern day nautilus.