Eutrephoceras dekayi with Hoploscaphites- Pierre Shale, Montana | River Walkers Minerals

Locale: Pierre Shale Formation, Glendive, Montana, USA 🇺🇸 

Age: Late Cretaceous (~70–80 million years old)

Dimensions: 1045g, 5 x 4.5 x 3.2”

An impressive natural association from the famous Pierre Shale of eastern Montana, this specimen features a large Eutrephoceras dekayi preserved in matrix alongside several smaller Hoploscaphites ammonites and numerous marine shell fossils. The dark shell of the nautiloid contrasts beautifully with lighter calcite-filled fractures and the fossil-rich surrounding matrix, creating a display with exceptional depth and character.

During the Late Cretaceous, this region lay beneath the Western Interior Seaway, a vast inland sea that covered much of North America. Specimens preserving multiple species together provide a fascinating glimpse into the diverse marine life that inhabited these ancient waters roughly 70–80 million years ago.

The prominent Eutrephoceras shell remains partially embedded in its original matrix, surrounded by smaller ammonites and shell material that have been naturally preserved together for millions of years. Pieces like this offer both scientific interest and a striking display, showcasing the remarkable abundance of life that once thrived in the ancient seas of Montana.

Please review all photos and videos carefully. You will receive this exact piece. This piece has been naturally repaired.