Other forms: ammonites
An ammonite is an extinct sea creature, a cephalopod distantly related to squids and octopuses. You can also use the word ammonite for the fossilized shells of these ancient animals.
The last ammonites died out 66 million years ago, and some ammonite fossils are over 400 million years old. Although their closest living relations don't have hard shells, ammonites did. These ancient mollusks' shells were flat, coiled disks. Their name comes from the creatures' resemblance to a coiled ram's horn: Ammonite is derived from Ammon (or Amun), the name of an Egyptian god who was portrayed wearing ram's horns on his head.