If you've ever been to, or lived in, or even flown over the central swath of North America, then you've seen the remnants of what was a uniquely fascinating environment. Scientists call it the Western Interior Seaway, and at its greatest extent, it ran from the Caribbean Sea to the Canadian Arctic.

Originally released by Knowledgemotion, 2018. Streaming video file encoded with permission for digital streaming by Infobase on February 21, 2020.

When Sharks Swam the Great Plains (12:40); .