5.6" Polished, Agatized Ammonite (Cleoniceras) - Madagascar
This is a beautiful, 5.6" wide, polished ammonite fossil from the Mahajanga Province of Madagascar. It's Early Cretaceous (Albian Stage) in age, or approximately 110 million years old and of the genus Cleoniceras. The fossil itself was replaced by agate and has been polished to reveal the beautiful, "oak leaf" shaped suture pattern of the animal.
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.