3.45" Iridescent Nautilus (Eutrephoceras) w/ Baculite - South Dakota

This is a beautiful, iridescent, fossil Nautilus (Eutrephoceras nebrascensis) from the Pierre Shale of South Dakota. It was prepared free of the hard concretion it was found in and was then remounted to it. The nautilus was found in association with one well preserved, partial Baculites ammonite and other smaller partials of the same genus. The base of the rock was cut flat for convenient, aesthetic display.

The shell of a Nautilus 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 which 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" in that 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. 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.
Eutrephoceras nebrascensis & Baculites sp.
Meade County, South Dakota
Pierre Shale - Baculites compressus/B. cuneatus Zone
Nautilus: 3.45" wide, Ammonite: 3.6" long, Entire specimen: 5 x 3.8"
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