HETEROMORPH AMMONITE

Ephamulina arcuata
Cretaceous, 100 million years
Madagascar
29 × 24 × 10 cm

Ammonites (Ammonoidea) are a distinct group of molluscs, the fossilised shells of extinct cephalopods. They were sea creatures whose shells were spiral-shaped. The uncoiled shell of this heteromorph ammonite indicates that it was a poor swimmer, drifting in the plankton, collecting small animals on long tentacles like modern jellyfish or moving slowly like a clam. Ammonites died out at the end of the Creataceous period, 65 million years ago, together with the dinosaurs. Thanks to the variety of their forms they remain a very popular collectors’ item.

This is a very nice example of a heteromorph ammonite – fossilized through pressure, heat, depth and time, consisting of calcite, pyrite and silicic acid. Its colouration varies between flesh-coloured, pinkish and sand-coloured nuances.