This Specimen has been sold.
Scarce 2 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.
Ammonites were predatory mollusks that resembled a squid with a shell. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus. Ammonites appeared in the fossil record about 240 million years ago and they barely survived several major extinction events. The last lineages disappeared 65 million years ago at the end of the Cretaceous.