An ancient sea once divided North America from north to south; 70-million-year-old creatures from its waters still shimmer like gemstones

A vast inland sea called the Western Interior Seaway once split North America from north to south, covering what is now South Dakota.

The sea existed during the Cretaceous period, about 69–72 million years ago, and was home to marine reptiles, sharks, and ammonites.

Ammonite fossils from the seaway still shimmer due to their mother-of-pearl composition.

These fossils are displayed at the Smithsonian's National Museum of Natural History in an exhibition called 'From these lands'.

Discoveries from the seaway continue to reveal insights into prehistoric marine ecosystems and Earth's history.