Ammonite Cleoniceras besairiei (polished half) – Madagascar

Cleoniceras besairiei is an extinct species of ammonite from the Cretaceous period, specifically from its early stage – the Albian (approximately 113–100.5 million years ago). This species is characterized by a tightly coiled spiral shell with very fine, subtle ribbing, giving the surface an almost smooth appearance. The internal chambers served to regulate buoyancy and allowed the animal to move through the water column.

The most well-known and best-preserved specimens come from Madagascar, where they have been preserved in exceptionally good condition. Many of them exhibit natural iridescence.

Ammonites like Cleoniceras were marine cephalopods, related to modern-day cuttlefish and octopuses. They had an external calcareous shell and lived mainly in the shallow seas of the world.