Ammonites are amongst the most popular fossil, and they have every right to do so. These beautiful spiral creatures are somewhat related to octupuses and squids, the only difference being that they went extinct 75 million years ago, along with the dinosaurs.
When ammonites originated, they were planktonic and tiny. Less than 1mm tiny. As they evolved and developed their strong protective shell, they gained size rapidly – especially the females, up to 400%!
Now, if you (like me) have always imagined these beauties as pacific, you might be in for a surprise. Ammonites were the predators of their time, feeding on almost any marine being including molluscs, fish and even other cephalopods.
Because their shells were covered in colors and patterns, it is suspected that ammonites preferred shallow waters with direct light. Their shells are coiled, and all contain a series of linked chambers. Their bodies were contained within the large final, open-ended section (the living or head chamber), from which the tentacles were extended to catch prey. As the animal grew, new chambers were added behind the head chamber.
Here are some beautiful examples of ammonite colors and patterns. All the photos come from Flickr Commons (links in the descriptions).