The skeleton was discovered in 1995 in the Sheyenne River Valley by Mike Hanson and Dennis Halvorson of Cooperstown. The remains were found on the land of Orville and Beverly Tranby of Cooperstown, who, along with Beverly's sisters, Gloria Thompson of Warren, Minn., Jacqueline Evenson of Edmonton, Alberta, Canada, and Susan Wilhelm of Princeton, Minn., donated this historic find to the North Dakota State Fossil Collection for study and exhibit. N.Y. The restoration and exhibition of the mosasaur fossil was funded by donations from the Amoco Foundation, Basin Electric Cooperative and Dakota Gasification Companies, Unisys Corporation, Montana Dakota Utilities Resources Foundation, the Coteau Properties Company, the Falkirk Mining Company, US West Foundation, North Dakota Paleontological Society, Central Dakota Gem and Mineral Society, North Dakota Geological Society, Fort Abraham Lincoln Corral of Westerners International, Sons of Norway, and William and Elizabeth Marshall. The North Dakota Heritage Center, located on the state capitol grounds in Bismarck, off Exit 159 on Interstate 94, is the headquarters of the State Historical Society of North Dakota. The largest museum in the state, it draws more than 100,000 visitors annually.
Admission is free.
It is open daily, closed only on New Year's Day, Easter, Thanksgiving and Christmas. In a cooperative agreement with the North Dakota Geological Survey, it also houses the State Fossil Collection. Mosasaur Fast Facts Mosasaurs were huge, some as long as 40 feet, and inhabited the world's oceans during the Cretaceous Period from about 90 million years to 65 million years ago. They were a large group of reptiles which included several species. Their prey probably included other mosasaurs, fish, turtles and invertebrates.