3.85" Pristine Fossil Ammonite (Hoploscaphites) - South Dakota

This is a 3.85" wide ammonite (Hoploscaphities spedini) specimen collected from the Fox Hills Formation of South Dakota. It has been exquisitely prepped, showing little signs of restoration. The color of the shell is enhanced by the insane amount of natural detail, including the raised bumps on the outer ridges that are characteristic of the Hoploscaphites genus.

This specimen is remounted to the rock it was found in, which was cut flat for sturdy and convenient display.

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.

What an ammonite would have looked like while alive.
What an ammonite would have looked like while alive.
Hoploscaphities spedeni
South Dakota
Fox Hills Formation - Trail City Member - Hoploscaphites nicolletti Zone
Ammonite: 3.85" wide, Entire specimen: 3.9 x 3.85"
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