9.8" Bumpy Douvilleiceras (Tractor) Ammonite - Huge Example!
This is a huge 9.1" wide Douvilleiceras ammonite from the Upper Cretaceous of Madagascar. This genus of ammonites has earned the local name "Tractor Ammonites", due to their distinctively bumpy surface and pronounced ridges making them resemble a tractor tire. This particular example has been nicely prepared to remove the hard rock and expose the shell.
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.