The Lakota called the Badlands “Mako Sica” or “land bad.” The early French-Canadian trappers referred to it as “les mauvais terres pour traverse” or “bad lands to travel through.” Seventy-five million years ago, this area was a lush underwater seaway filled with creatures such as mosasaurs, plesiosaurs, diving birds, fish, baculites, and ammonites (Figure 2).
The Stilwell fossils of Cretaceous age (Figure 3) were deposited in a black mud that accumulated on the sea floor from 82 to 70 million years ago (Figure 4). The Pierre Shale is part of the extensive Western Interior Seaway of North America (Figure 5). Museum visitors can view a changing geographic representation of the seaway on a wall-mounted flat screen monitor within the Dinosaurs in Their Time exhibit. The seaway extended from the Gulf of Mexico, Florida, and southern Gulf Coast, north through Texas, Kansas, Colorado, Wyoming, Montana, the Dakotas, and the Canadian Provinces of Alberta and Saskatchewan. This vast waterway terminated in the Artic region of Canada. At the time of the Pierre Sea, the ice sheet-free greenhouse to hothouse paleoclimate was much warmer than it is today, creating the highest sea levels in earth’s history. Sea level rises and falls were primarily controlled by the presence or melting of glaciers in the polar regions, the shifting of the continents, and the uplifting of proto-Rocky Mountains by plate tectonics.
Fast forward to the Wild West of the 1890’s, and dealers such as Stilwell found and sold fossils to museums and private collectors. Knowledge of Badlands fossils spread as far as Europe, and by 1889 Bayet wanted some for his own collection.
Next, in our final post of this series, we will delve into the Stilwell-Bayet correspondence in search of clues about how fossils were bought and sold over a century ago.
Joann Wilson is an Interpreter for the Department of Education and a volunteer with the Section of Invertebrate Paleontology. Albert Kollar is Collections Manager for the Section of Invertebrate Paleontology. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.