Polished Cleoniceras Ammonites, fossils for sale from Madagascar. Dating from the Cretaceous Period at a majestic 120 million years old, this gorgeous large Madagascan Ammonite is an exciting piece of history. This particular Ammonite, of the Cleoniceras species, measures 16 cm wide. These wonderful fossils display intricate swirling patterns and brown and caramel tones. The ammonite has been carefully hand-polished to reveal its rich golden brown and cream calcite replacements and impressive fern-like suture patterns: these replacements occurred over a very long period of fossilisation, wherein water dissolved the original hard parts of the ammonite shell and replaced it with mineral matter. What Are Ammonites? Ammonites are a group of extinct molluscs which somewhat resembled a shelled squid when they were alive. These ancient sea creatures had tentacles like the modern octopus, and spiral shells like Nautilus creatures. They first appeared on the fossil record 240 million years ago, in the Triassic Period, and died out 65 million years ago with the dinosaurs during the Cretaceous-Tertiary Mass Extinction Event. The fossilised remains of these sea creatures are perhaps the most popular fossils on the market today. This particular ammonite is a member of the Cleoniceras species of ammonites. How Old Are Ammonites? This ammonite dates back to the Cretaceous Period, meaning it is 120 million years old. These ammonites are examples of fossils from the Cretaceous period, but there are many ammonites such as Perisphinctes ammonites which are even older fossils from the Triassic period, at 248 million years old! Where Do Ammonites Come From? This ammonite was originally found in the jungles of Mahajanga on the North West Coast of Madagascar. Madagascar is famed for its riches of fossils and natural diversity, and a wide variety of fossils and crystals can be found there.