| Figure 5 The sediment Opalinus Clay takes its name from the frequent occurrence of the fossil ammonite Leioceras opalinum. |
| The presence of an ammonite is generally disclosed by a bit of iridescent shell material visible on the edge of the concretion. |
| On top of that, coprolites, as palaeontologists politely describe fossil faeces, have turned up with ammonite shells in them. |
| These structures improve the resistance of the ammonite septum to pressure upon its main surface in both adapical and adoral directions. |
| In North America only Mexico has a detailed ammonite stratigraphic zonation developed for much of the Kimmeridgian. |
| The in situ position of many of these jaws is of considerable interest and suggests that post-mortem disturbance of the ammonite was not great. |
