the ammonite pleuroceras salebrosum, from the lower jurassic of southern germany

ammonite ancient animal background calcite cephalopod circle closeup detail environment evolution extinct fossil fossilization fossilized geologic geology germany history invertebrate isolated jurassic macro mineral mineralogy mollusc natural nature nautilus old paleontology pattern pleuroceras pliensbachium prehistory rock salebrosum science shell snail spiral stone swirl textured white