Voorbeelden van ammonoid

• The zone is 170 m thick, and ammonoids and other fossils occur as imprints in mudstones and as shell-rich layers in sandy turbidites.

• The diversity of the ammonoid assemblage in this zone has increased to five genera and about 15 species.

• Quite detailed correlations are not possible yet, but one can clearly see a westward diachronism in the first occurrence of some ammonoid genera.

• Abundant concretions at several levels contain well-preserved ammonoids, bivalves and occasional fish.

• Moreover, in the study of a highly diversified group such as the ammonoids, we believe that making too many generalizations can be risky.

• This zone is widely distributed, 20-150 m thick, and contains the most diverse ammonoid assemblage with seven genera.

• The number of ammonoid genera is greatly reduced to four, combined with a gradual shallowing-upward trend in the succession.

• Brachiopods, cephalopods (ammonoids and one nautiloid) and bivalves are rare.

• Plasticity of developmental timing as the underlying cause of high speciation rates in ammonoids.

• However, the preservation of the collected material is too poor and the total number of ammonoids from single beds is too scarce to allow such a revision to be undertaken.

• They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopuses, and cuttlefish, and more distantly to the nautiloids.

• They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopodes, and cuttlefish, and more distantly to the nautiloids.

• They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopuses and cuttlefish, and more distantly to the nautiloids.

• It is the outermost or last chamber in the shell of a nautiloid or ammonoid.

• In the seas, a novel major group of ammonoid cephalopods called clymeniids appeared, underwent tremendous diversification and spread worldwide, then just as suddenly went extinct.