2.6" Iridescent Nautilus (Eutrephoceras) w/ Ammonites - South Dakota

Iridescent Nautilus (Eutrephoceras) w/ Ammonites - South Dakota #209692

This is a beautiful, iridescent, fossil Nautilus (Eutrephoceras sp.) from the Fox Hills Formation of South Dakota. It was expertly prepared mostly free of the hard concretion it was found in. The nautilus was found in association with two, well preserved, unidentified ammonites. The base of the rock was cut flat for convenient, aesthetic display.

A nautilus's shell is made up of two layers. The inner layer has the iridescent shine, while the outer layer provides protection from external forces. Inside the shell are septa that divide the living area of the shell into compartments and help the animal maintain balance and position in the water column.

Nautilus are "living fossils": species similar to this one still exist in our oceans!

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.

More about ammonites