This is a Jurassic limestone ammonite fossil from our Science collection. It was found in Somerset, UK and is between 200 and 240 million years old.
Ammonites are one of the most well-known fossils. They possess a ribbed spiral-form shell. Ammonites lived in the oceans between 240 and 65 million years ago, when they became extinct along with dinosaurs. The name "ammonite" derives from the Greek god Ammon, who was ram-horned.
Ammonites belong to a group of predators called "cephalopods", which includes the octopus, squid and cuttlefish. They moved by jet propulsion, expelling water through a funnel-like opening to propel themselves in the opposite direction. They typically lived for two years, and they spent their time in shallow waters. We know this from their diet and also the fact that their shells would have been unlikely to have withstood the pressure of deeper waters.