2.7" Discoscaphites Gulosus Ammonite - South Dakota
This is a large, 2.7" wide Discoscaphites gulosus ammonite specimen from the Fox Hills Formation of South Dakota. It's been wonderfully prepared nearly free from the hard concretion it was found in.
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.