Ammonite
Ammonite Information
Ammonites were marine molluscs related to modern cephalopods like octopuses and squids. These creatures flourished for over 300 million years before their extinction about 66 million years ago, around the same time as the non-avian dinosaurs. The name “ammonite” is derived from the Egyptian god Ammon, who was often depicted with ram’s horns resembling their coiled shells.
Ammonites had intricate, chambered shells that helped them control buoyancy, enabling them to move up and down in the water column. Despite their resemblance to nautiluses, ammonites were more closely related to coleoids, potentially possessing eight arms. These shells often formed a flat spiral but could exhibit various shapes, including loose spirals, helical forms, and even unique structures like the knot-shaped Nipponites mirabilis found in Japan.
Their shells are abundantly found as fossils worldwide, with remarkable preservation in some cases. Although the soft parts of ammonites are rarely fossilized, recent discoveries have provided more insights. Through the study of living cephalopods, scientists continue to uncover the mysteries of these ancient ocean dwellers.
Ammonite Facts
- Ancient Origins: The subclass Ammonoidea, commonly referred to as ammonites, first appeared approximately 450 million years ago during the Devonian Period
- True Ammonites: Ammonoidea includes a more exclusive group called Ammonitida, known as the true ammonites, which thrived during the Jurassic Period about 200 million years ago.
- Mass Extinction: Most ammonites met their demise at the same time as the non-avian dinosaurs, around 66 million years ago, at the end of the Cretaceous Period.
