Ammonites

Ammonites were ocean-dwelling animals belonging to the cephalopods, the group that includes modern squid, octopuses and nautiluses. They are best known for their coiled shells, although some species developed unusual shapes.

As an ammonite grew, it added new chambers to its shell. The animal occupied the outermost chamber, while the earlier chambers helped control buoyancy. A cut and polished fossil can reveal the internal divisions that formed this remarkable structure.

Ammonites disappeared around 66 million years ago, during the mass extinction at the end of the Cretaceous Period. Their fossils are found around the world and help scientists compare and date ancient rock layers. Today, their distinctive shapes make them fascinating specimens to study, collect and display.