Western Interior Seaway - Invertebrate Collection

The Western Interior Seaway was a warm, shallow sea that once stretched across the center of North America during the Late Cretaceous, around 100 to 66 million years ago.

The American Museum of Natural History Invertebrate Paleontology collection holds more than 400,000 fossil invertebrates from the Western Interior Seaway, collected from over 500 localities in the northern Great Plains. The collection was primarily built through decades of fieldwork by Curator Emeritus, Dr. Neil Landman and his collaborators, including many avocational paleontologists. The collection is particularly strong in ammonites and other mollusks, but a wide range of other invertebrates, such as bryozoans, sponges, and echinoderms, are also represented.

You can find out more about the diverse marine life from the Western Interior Seaway and view selected specimens from our collection and several other museums on the Cretaceous Atlas of Ancient Life. A dataset comprising 13,149 occurrences is available to view and download on GBIF.