2.2" Cretaceous Fossil Ammonite (Calycoceras) - Texas
This is a 2.2" fossil ammonite (Calycoceras tarrantense) from Dallas County, Texas.
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. The last lineages disappeared 65 million years ago at the end of the Cretaceous.