Large Polished Ammonite cleoniceras
This large polished ammonite cleoniceras is a superb example. While one side shows the superb fern like ‘suture’ patterns it has stunning red opalescence on the other. This opalescence is formed when the mineral aragonite replaced the ammonite shell. These fossils, also sometimes known as fire ammonites. These fossils date back to the Cretaceous period, 120 million years ago. This ammonite is from the Mahajanga jungle on the north west coast of Madagascar.
Ammonites have been extinct for 65 million years. They are a form of Cephalopod, a large and diverse group of marine molluscs. These first appeared in the Devonian Period, over 4oo million years ago. The soft body tissues of the ammonites, being so delicate are rarely preserved. It is generally the much harder outer shells that are fossilised. As the ammonite grew larger it constantly added new chambers to its shell. The actual creature only lived in the largest, and most recently formed chamber. The name Ammonite, has derived from from the name of the Greek God ‘Ammon’. Ammonites were plankton feeders, with long tentacles, and they swam upright. Altogether, there were in the region of four thousand different species.
Ammonites became extinct 65 million years ago, at the same time as the dinosaurs. Although Ammonites themselves have long been extinct, the squid and octopus that swim in our seas now, are closely related.