Ammonite fossil!

The fossil in the image appears to be a cross-section of an ammonite. Ammonites are a group of extinct marine mollusks within the class Cephalopoda, related to modern squids, octopuses, and nautiluses. The distinctive spiral shell with internal chambers is a key characteristic of ammonites. The chambers are divided by septa, which are the walls you see in the fossil, and the intricate patterns are typical of the internal structure of ammonite shells.