1.9" Carboniferous Ammonite (Muensteroceras) Fossil - Indiana

Carboniferous Ammonite (Muensteroceras) Fossil - Indiana #126192

This is 1.9" wide fossil ammonite of the species Muensteroceras parallelum, collected from the Rockford Formation of Rockford, Indiana. The outer shell is gone leaving the chamber patterns exposed.

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. True ammonites appeared in the fossil record about 240 million years ago. The last lineages disappeared 65 million years ago at the end of the Cretaceous.

What an ammonite would have looked like while alive.

More about ammonites