When Crocodiles Ruled banner

Teacher's Guide Index

square bulletPaleontology and geologic time
square bulletHow fossils are formed and preserved
square bulletWannagan Creek discoveries
square bulletWorld Change Central
square bulletHow to determine the age of fossils
square bulletAnimal evolution
square bulletExtinctions
square bulletContinent shifting
square bulletClimate changes
square bulletAfter the dinosaurs died out--the survivors
square bulletDiorama of subtropical habitats
square bulletCrocodilians--past and present
square bulletCrocodilian biology and behavior
square bulletCrocodiles and people
square bulletOther animals at Wannagan Creek

An exhibition produced by the Science Museum of Minnesota. The exhibition is presented by Koch and is made possible with major support from the National Science Foundation.

By sixty-five million years ago dinosaurs no longer roamed this planet. Scientists aren't entirely sure what killed them off. One theory is that a large meteorite impact or volcanoes created clouds of dust, which blocked out sunlight and lowered the earth's surface temperature. Other theories attribute the extinction to topographic changes, such as continental drift and sea level fluctuations. These changes might have fragmented habitats, leading to a slow extinction of the dinosaurs over millions of years. Although many creatures went extinct along with the dinosaurs, some did not. These survivors, which included our own tiny ancestors, inherited a world that was initially short on large predators, with crocodiles as an exception.

What happened in those intervening 60 million years? This span of geologic history, known as the Cenozoic Era, was the time when mammals began to diversify and evolve into groups that surround us today. Continental plate movements had a huge impact on species migration and climatic changes. Scientists know much more about the creatures that lived during the Cenozoic than they do about dinosaurs and the animals that preceded them. This is because the fossil record from the Cenozoic is much more complete.

When Crocodiles Ruled picks up the story of earth in the Paleocene Epoch, which occurred immediately after the dinosaurs' extinction. Although the Paleocene is just one epoch among many leading up to the present day, the exhibit also encourages visitors to think about the rest of geologic time. The exhibit and its components are based on fossil discoveries from a field site in western North Dakota known as Wannagan Creek. The Science Museum of Minnesota's paleontology department has been excavating and studying fossils from this site for over twenty years. The rich fossil assemblage that has been uncovered there gives us a chance to reconstruct an entire ecosystem, rather than just a few isolated animals.

In this exhibit, visitors are able to walk through life-size dioramas that show what we believe North Dakota looked like 60 million years ago. Rather than dry, open ranch land, Wannagan Creek was once a subtropical swamp filled with crocodiles! After being immersed in this swampy environment, visitors can enter World Change Central, where they learn about geologic time, the evolution of species, and explore how the world's climate is always changing. This area shows why the discoveries of paleontology are so relevant to science. The third area, the Field Camp, shows visitors the methods paleontologists use to make those discoveries. Visitors to the Field Camp learn how fossils are excavated and studied, try their hand at assembling the skeleton of an aquatic reptile known as a champsosaur, and search for microfossils. They exit the exhibit back through the diorama area with a new understanding of the work done at Wannagan Creek and a better idea of what western North America was like once the dinosaurs disappeared.

Paleontology and Geologic Time >

Teacher's Guide | After the Dinosaurs | Exhibits