A unique nautilus fossil with exposed chambers that exhibit a thin layer of calcite. The open section of the fossil clearly exhibits the septa separating the chambers and the siphuncle running directly along the center of the shell. There are also small sections of iridescence caused by aragonite. This specimen measures 3"x3"x3.5".
Fossils found in the Pierre Shale Formation (83-69 million years ago) are part of the Western Interior Seaway which stretched across the Great Plains and much of the Rocky Mountain region, connecting the Arctic Ocean to the Gulf of Mexico. This stretch of the Cretaceous Period between 113-66 million years ago is responsible for many aquatic fossils found in North America.
Locality: Elk Creek, Pierre Shale Formation, South Dakota, USA
Species: Eutrephoceras nebrascansis
