2.1" Jurassic Ammonite (Microderoceras) - Charmouth, England
This is a 2.1" wide, calcite replaced ammonite (Microderoceras birchi) fossil from Charmouth England. There is a tiny specimen of the same species right next to it. They have been nicely prepared using mechanical tools to remove the surrounding limestone. The rock has been cut flat so that it stands up nicely without the need for a display stand.
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.