cross-section of ammonite fossil

ammonite ammonites ammonitida ammonoid ammonoidea ancient animal cephalopod cephalopoda chambers clean cut cleoniceras cretaceous cross crosssection extinct fossil fossilization fossilized fossils geological geology geometry index interior internal invertebrates jurassic longitudinal madagascar marine mollusc mollusk nautilus old paleontology paleozoic pattern petrified prehistoric prehistory rock sample shape shell snail spiral stone cross-section visible