Grasslands National Park in southern Saskatchewan is well known for its rolling hills, breathtaking badlands, and inquisitive prairie dogs. One sign instructs visitors to “shoo the prairie dogs away with enthusiasm”. But the park is also one of the best places in the world to understand how this little mammal, and all its furry mammalian relatives, came to replace the dinosaurs.
That’s because the park is rich in fossils that tell us of the dramatic environmental and faunal changes that have occurred since the extinction of the dinosaurs.
This past summer, I led a small team of intrepid female palaeontologists exploring the park as part of my research into the evolution of mammals.
Wherever we went in the East Block (the park is divided into separate eastern and western chunks), it was difficult to miss the coal seam that marks the Cretaceous-Paleogene Boundary (KPg), the end of the dinosaurs and the beginning of the age of mammals, about 66 million years old. At times we literally tripped over the moment in time that dinosaurs went extinct.
The rocks at the KPg boundary record an environment much more tropical than modern Saskatchewan and a mammal fauna very different from today.
On the very top of the hills, we uncovered the first 20 million-year-old fossil sites ever found in the park. These much younger rocks record an environment that would have looked more familiar to us today, with a mix of forest and grassland. It was an environment populated by a variety of mammals with hooves, including three-toed horses, rhinoceroses (yes, rhinos!), and relatives of the living pronghorn.
On future expeditions to Grasslands National Park we will continue to search the rocks immediately after the KPg for fossils of early primate-like mammals (Plesiadapiformes) and other extinct mammal lineages.
In comparing such specimens with fossils from the younger overlying layers we hope to paint a picture of how mammals responded to the extinction of the dinosaurs and to the extreme environmental changes that have occurred over the past 66 million years.
And how this all combined to produce the curious little prairie dogs.