1.4" Cretaceous Fossil Clam - South Dakota

This is a small 1.4" Goniamia Americana specimen collected from the Fox Hills Formation of South Dakota. It's been wonderfully prepared in the hard concretion it was found in.

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.