The common name ammonite was given to an order of extinct cephalopods centuries ago because of their resemblance to the ram-like horns of Ammon, the Egyptian god of life and reproduction. This spiraled shape, signifying eternity and thus eternal good fortune led to the ammonite becoming a lucky talisman or good-luck charm.
Ammonites first appeared 438 million years ago during the later portion of the Paleozoic Era. They survived almost 370 million years until an asteroid hit the earth ending the Cretaceous Period and the Mesozoic Era 65 million years ago.
Like their present day relatives the squid and octopus, the ammonite had a group of prehensile (capable of grasping) tentacles or arms that encircled the mouth, a distinct head with well-developed eyes, and powerful jaws that resembled an upside-down parrot beak. The tentacles often had suckers on them and were used for swimming, but also for catching, squeezing and pulling prey to their mouths. The ammonite also had a modified foot called a hyponome shaped like a muscular spout or funnel. The ammonite used this spout to quickly thrust out water, allowing it to dart rapidly through the water like a squid.
The walls separating the chambers of the shell are called septa, and these often formed lines on the outside surface of the shell called suture patterns. The gaseous and fluid content of these chambers could be moderated through an internal connecting tube called the siphuncle. The siphuncle acted like a siphon, removing any fluids in the chambers by a process called osmosis. This ability allowed the ammonite to control its vertical movement in the water. Humans later adapted this technology to create the ballast systems used by modern day submarines.