Ammonite is a fossilized marine mollusk that lived during the Jurassic and Cretaceous periods. It is characterized by its spiral-shaped shell, which is divided into chambers filled with gas or fluid. The shell is made of aragonite, a form of calcium carbonate. Ammonites are found in many parts of the world, including Europe, North America, South America, Africa, and Australia. They are an important part of the FOSSIL record, providing evidence of the evolution of life on Earth.