Ammonites are an extinct group of cephalopods that were very rich in form. There are 1500 known genera of ammonites. Thanks to their variety of forms ammonites are a popular collector's item. Their shell – rolled up in the manner of a logarithmic spiral – recalls that of a snail, but this is not the case with all ammonites. The species Crioceras Nolani has a flat, spiral shell, where no coil is in contact with the other.

Why the shape developed in this way is unknown. Possibly this species lived in the benthic zone at the lowest level of the sea, so there was no need for a shell suitable for swimming. The spines decorating the animal's shell served as protection for the ammonite, which was either sedentary or could only move slowly on the sea floor.

The specimen presented here is in very fine condition, showing only restorations to the long spines.