Scarce 1.9 Inch Desmoceras Ammonite

Here is a type of ammonite you don't see as often from Madagascar. It's of the genus Desmoceras and is much thicker than the common Cleoniceras. The shape of the chambers is also different. It's beautifully agatized with some of the chambers being lined with calcite crystals.

About Ammonites

Ammonites were predatory, marine mollusks that thrived during the Paleozoic and Mesozoic eras, particularly in the Jurassic and Cretaceous periods, before going extinct around 66 million years ago. These creatures are characterized by their coiled, spiral shells, which resemble the modern-day nautilus. Ammonite shells were divided into chambers; as they grew, they built new chambers and sealed off the old ones. These chambers were filled with gas, which helped them control buoyancy in the ocean.

The outer shell of ammonites often displays intricate ribbed or ridged patterns and their fossils sometimes show a wide range of beautiful colors due to mineralization over time. The shells fossilized well, making ammonites abundant in the fossil record.. In addition to being popular in fossil collections, ammonites are valuable in geological studies, as they serve as index fossils, helping scientists date rock layers and understand the Earth's prehistoric environments.

Artist's reconstruction of an ammonite, by Nobu Tamura

More about ammonites