Ammonites

Ammonites lived from around 400 million to 65 million years ago.

The group shown here are all from the Mesozoic era, the same time as the dinosaurs. This was when the ammonites were at their most diverse and successful.

The fossils we see are just the hard shells. The animal itself was a squid-like organism that lived inside.

Where people can picture an ammonite, the familiar coiled shell is what they will probably have in mind. Yet as the specimen on the top left shows, some ammonites had an “uncoiled” shell.