7.1" Fossil Ammonite (Placenticeras) - South Dakota

This is an ammonite (Placenticeras meeki) that was collected from the Cretaceous-aged Pierre Shale of South Dakota. You can really feel the heft of the partial pyrite replacement of this ammonite when you hold it in your hand. There is some restoration along one edge.

Comes with a display stand.

These 70 million year old ammonites lived when South Dakota was a shallow inland sea. They were found preserved in concretions when split open. They then had to be hand-prepared to remove the hard rock surrounding them from their shells, a very time consuming task.

Ammonites were predatory cephalopod mollusks that resembled squids with spiral shells. They are more closely related to living octopuses, though their shells resemble that of nautilus species. True ammonites appeared in the fossil record about 240 million years ago during the Triassic Period. 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.
Placenticeras meeki
Cheyenne River, South Dakota
Pierre Shale
7.1" Wide
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