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 cephalopod mollusks that resembled squids with spiral shells. They are more closely related to living octopuses, though their shells resemble that of nautilus species. True ammonites appeared in the fossil record about 240 million years ago during the Triassic Period. 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