Origin: Pierre Shale Formation, Elk Creek, South Dakota
These extinct cephalopods lived 73 million years ago, floating in warm oceans with coiled shells and gas-filled chambers for buoyancy. Preserved in protective concretions, these fossils exhibit colorful iridescence. Their formation is associated with ancient meteorite impacts and tsunamis, which shaped the seafloor into fossilized mud balls of various sizes. These stunning specimens are a window into Earth’s ancient marine ecosystems and geological events.
