What happened in North America after the dinosaurs died out? In the Primeval Swamp, you can travel back 60 million years to find out. See what North Dakota looked like once crocodiles replaced dinosaurs at the top of the food chain. Real fossils and interactive exhibits address the topics of climate change and evolution. When Crocodiles Ruled is the product of more than twenty years of Science Museum fieldwork and research at Wannagan Creek, North Dakota.