A few weeks ago Ferrebeekeeper featured a post about belemnites, extinct cephalopods from the Mesozoic which teemed in immense schools through the reptile-haunted oceans of that bygone era. Yet belemnites were certainly not the only cephalopods which swam in the Mesozoic seas. Numerous shelled cephalopods—the ammonites—were widespread in every sort of marine habitat. Ammonites are personal favorites of mine so I am not going to write a comprehensive explanation/description of the subclass. Instead I wish to provide you with an idea of how big ammonites could get by providing a few pictures of large ammonite fossils which have been discovered. Imagine these monsters jetting through the water with huge tentacles and big intelligent eyes scanning for giant predatory reptiles and you will have a better idea of the Mesozoic Oceans!