One of the more popular items in our Fossil Dig is an ammonite. This fossil was once an animal that swam in shallow marine seas. They are mollusks with soft bodies, .ike octopus and squid, that also had tentacles that surrounded beak like jaws. The closest living relative is a chambered nautilus. The ammonite's ability to swim was due to the unique construction of its shell that contains many chambers filled with air which provides buoyancy so it could float. They were very plentiful in their day.