Bearpaw Sea

Trinacromerum, a short-necked plesiosaur, rises from the bottom of the Museum's Bearpaw Sea exhibit.

Throughout most of the Cretaceous, a shallow seaway covered the western interior of North America. It stretched from the Arctic Ocean to the Gulf of Mexico. At times, it virtually covered the entire province of Alberta.

The Bearpaw was the last of these seas to cover Alberta. When it receded some 70 million years ago, it left a thick layer of marine deposits we call the Bearpaw Formation. These dark shales form the base of the hoodoos east of Drumheller.

The Bearpaw Sea supported a rich diversity of life. Some of its inhabitants were immobile, filtering small particles of food out of the water. Some, like the crayfish, survive today. Others, ammonites among them, did no not. Clams moved through the mud, their burrows now preserved as trace fossils. The thick oyster beds near Drumheller originated at this time. Worms burrowed through the substrate and baculites hung overhead or jetted backwards through the water. Many-armed cuttlefish were preyed upon by large marine lizards; the mosasaurs, close relatives of the modern Komodo dragon. Sharks and plesiosaurs were other common predators in the Bearpaw Sea.

This document was prepared by Wayne Hortensius, Calgary, Alberta, Canada for the Royal Tyrrell Museum Cooperating Society. All information © 1995 Royal Tyrrell Museum. All Rights Reserved.
Updated: April 8, 1995

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