Ammonite fossils

The Guille-Allès collection includes a large number of fossilised ammonites, shelled molluscs that died out around 66 million years ago. Ammonite fossils are found all over the world, sometimes in very large concentrations, and are easily recognisable from the distinctive spiral shape of their shells.

There are fourteen ammonite specimens on display here, including the large Asteroceras obtusum from the Lower Jurassic period, set in Blue Lias limestone substrate. This was collected from Lyme Regis, Dorset.

The thirteen smaller specimens also date from the Lower Jurassic Period, and were all collected in the British Isles. Of particular interest is one example that shows the suture lines where the outer shell met the septa, the thin walls between the ammonite’s internal chambers. Another specimen displays the remains of the body chamber, now filled with calcite.