Ammonite jaw apparatuses from the Sinemurian (Lower Jurassic) of Dorset and their taphonomic relevance

The occurrence of ammonite jaw apparatuses in situ within concretions from the Sinemurian (Lower Jurassic) of Black Ven Cliff, Charmouth, Dorset, prov ides evidence of burial of the ammonites with soft parts intact and this is of importance in considering the origin of the concretions. The lower jaws (anaptychi) of arietitid and eoderoceratid ammonites are preserved and thr ee examples of upper jaws are recorded in the species Asteioceras stellare. Although usually accepted as being entirely of organic composition, the an aptychi of A. stellare have an outer calcareous layer.