North Dakota overrun by Sharks! 

Well that's not exactly correct, but take a look at the map below. 

The Western Interior Seaway covered a large portion of the central United States 75 million years ago.  This sea was quite shallow and contained sharks, mosasaurs, sea turtles and lots of other vertebrate and invertebrate animals that became fossilized.

A tremendous number of fossils have been found in the Pierre Shale formation.  This formation is normally overlain with hundreds of feet of glacial drift and other sediments.  Lots of rivers in North Dakota have washed away this drift and exposed the Pierre Shale.  The most diverse assemblage of fossils ever found in the Pierre Shale in North Dakota is located in Griggs County about 8 miles southeast of Cooperstown.  The most well-known is the mosasaur that was found on this site and now resides in the North Dakota Heritage Center in Bismarck.

There are more links to additional information on the Cooperstown Mosasaur at the bottom of this page.


John Hoganson, paleontologist at the North Dakota Geological Survey in Bismarck, standing in front of the Mosasaur found near Cooperstown, North Dakota.

This is a replica of the skull in the Griggs County Museum.

North Dakota has several other paleontological museums.  The Dakota Donosaur Museum in Dickinson, North Dakota has 14 full scale dinosaurs as well as 50 display cases of rare rocks, minerals and fossils of all kinds found in North Dakota.

One of the most complete dinosaur mummies ever found is revealing secrets locked away for millions of years, bringing researchers as close as they will ever get to touching a live dino.  This was found in the Hell Creek Badlands Formation in North Dakota.  The fossilized duckbilled hadrosaur is so well preserved that scientists have been able to calculate its muscle mass and learn that it was more muscular than thought, probably giving it the ability to outrun predators such as Tyrannosaurus rex.

The Dinosaur capital of North Dakota in Marmarth contains 65 million year old dinosaur fossils including triceratops and tyrannosaurus rex. 

More Links to the Cooperstown Mosasaur

  1. Cooperstown Pierre Shale Site

  2. Corridor of Time Exhibit

  3. Plioplatecarpus

  4. A New Species of Mosasaur Discovered in North Dakota?

  5. Mosasaur were Reptiles, but not dinosaurs

  6. US And Canadian Fossil Sites -- Data for North Dakota

  7. Invertebrate Fossils from the Pierre Shale

  8. Summer Dig Planned for giant sea turtle remains



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