During the Late Cretaceous period, rivers flowed east from the Rocky Mountains to the inland sea that once covered what is now eastern North Dakota. The weather was similar to that of south Florida, and deposits resembling the Mississippi Delta built up around what is now known as the Hell Creek Formation south of Bismarck/Mandan. It was an ideal habitat for dinosaurs.

The Dromaeosaurus, or “running reptile,” was a particularly fierce predator. It was about the size of a large dog – with its tail, it was about six feet long. It was lightweight and speedy and ran on its hind legs with its tail held erect. The Dromaeosaurus had grasping hands and serrated teeth, and its nastiest weapons were large, slashing, sickle-shaped claws on the second toe of each foot. Its brain was large – indicating it was probably smart enough to hunt in packs.

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