Decorah’s giant sea scorpion, the Pentecopterus decorahensis, is officially home! Join in exploring and celebrating the life-sized model of Decorah’s most famous fossil discovery. Learn more about the discovery and how this 3D rendering was created. Beginning in the spring of 2023, the model will be publicly displayed in its long-term home in Valders Hall of Science at Luther College.
Approximately 465 million years ago during the Ordovician Period, an impact event occurred in what is now Decorah, Iowa. The result was a crater with a diameter of 3.5 miles (5.6 km).
Soon after the crater was created through the impact of the meteor, it filled with ancient sediment and then was buried under even more sediment. Millions of years later, the Upper Iowa River eroded some of that sediment away and created the bluffs and hillsides that now surround Decorah.
The Decorah Impact Crater discovery provides scientists with a new opportunity to learn more about impact events and crater processes. The crater basin also created a unique environment in which an exceptional fossil record was preserved, offering insights into life on Earth during a critical period in the evolution of complex life.
The Decorah Crater might still be undiscovered if not for the curiosity and persistence of local resident Jean Young and her work for the Iowa Geological Survey. Learn more about Jean by clicking on “Crater Discovery” below.
The most famous fossil discovery from the Decorah Crater made so far is Pentecopterus decorahensis, a giant sea scorpion. The term ‘sea scorpion’ is an informal name for a type of arthropod called a eurypterid (yew-RIP-ter-id). Like other arthropods (insects, shrimp, lobsters, etc.), eurypterids had a segmented body and jointed limbs with a flexible organic exoskeleton. While It looked like a scorpion, it lived in water and used its tail for navigating rather than stinging. It also had paddle-like rear legs adapted for swimming.
Pentecopterus decorahensis was a large apex predator during the Ordovician period, approximately 465 million years ago. Adult and juvenile fossil species were discovered in a fossil bed under the Upper Iowa River near Decorah. The fossils were preserved in sediment layers formed where the shallow sea covering Iowa at the time flooded the Decorah Crater.
Learn more by clicking on the “Fossil Discoveries” icon above!
Grab a piece of history for the whole family! Celebrate our local fossil celebrity, the giant sea scorpion Pentecopterus decorahensis.
Stop by the Decorah Visitor Center, at 507 W Water Street, to purchase sea scorpion shirts and postcards designed by local Decorah Artist Mark Whelan. Shirts are available in adult and kid sizes. When you stop by we will talk about who would win in an underwater battle — you or the Pentecopterus decorahensis?!
Understanding and celebrating the Decorah Crater is an important and growing feature of community pride and self-identification in Decorah and Winneshiek County. Join community members and organizations in supporting public outreach, school-based education, and tourism-promotion efforts based around the Decorah Crater, the unusual life that inhabited it, and the unique regional geologic history of the Decorah area.
Donations of all sizes are appreciated to help this project grow! Donations are received and held by Northeast Iowa RC&D, a 501(c)3 organization and one of the partnering organizations working on telling the story of the Decorah Crater.
Project partners are currently focused on two initiatives.
Laura Peterson, Professor of Environmental Studies, Luther College
Birgitta Meade, Decorah Educator
Tom St. Clair, Decorah Resident
Steve St. Clair, Decorah Resident
Lilly Jensen, Northeast Iowa RC&D
Stephanie Fromm, Winneshiek County Development
Alyssa Ritter, Visit Decorah
Jessica Rilling, Decorah Area Chamber of Commerce
Hanna Schmitt, Winneshiek County Conservation
If you would prefer to donate via check, please send a check with “Crater Projects” in the memo line to the address below.
Northeast Iowa RC&D
PO Box 916
Postville, Iowa 52162
