Pair of Polished Ammonites from 150 to 170 mm. Ammonoids (Ammonoidea), commonly known as ammonites, 1 are a subclass of extinct cephalopod mollusks that existed in the seas from the Devonian (about 400 million years ago) to the end of the Cretaceous (65.5 million years ago). 2 Thanks to their rapid evolution and global distribution, they are excellent guide fossils for dating rocks and have made possible the elaboration of biozone successions of great biostratigraphic precision.
