2.1" Fossil Ammonite (Hoploscaphites) - South Dakota

This is a 2.1" Hoploscaphites (Jeletzkytes) spedeni ammonite specimen collected from the Fox Hills Formation of South Dakota. It's been wonderfully prepared in the hard concretion it was found in. There is a second smaller ammonite within the rock as well, likely of the genus Scaphites.

These 70 million year old ammonites lived when South Dakota was a shallow inland sea. It was found preserved in a concretion that was split open. It then had to be hand prepared to remove the hard rock surrounding it from the shell, a very time consuming task.

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.

Hoploscaphites (Jeletzkytes) spedeni & Scaphites sp.
Corson County, South Dakota
Fox Hills Formation - Trail City Member
Ammonite 2.1" wide, rock is 4.8 x 2.7"
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