2.6" Fossil Ammonite (Sphenodiscus) - South Dakota

This is a 2.6" Sphenodiscus sp. ammonite specimen that was collected from the Fox Hills Formation of South Dakota

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.
SOLD
DETAILS
SPECIES
Sphenodiscus sp.
LOCATION
Corson County, South Dakota
FORMATION
Fox Hills Formation
SIZE
Ammonite 2.6" Wide
ITEM
#180838
GUARANTEE
We guarantee the authenticity of all of our
specimens. Read more about our
Authenticity Guarantee.