Tertiary (Paleogene) Period

Soon after the retreat of the great Western Interior Seaway of the Cretaceous Period, great coal swamps covered eastern Wyoming. This fossilized tree stump was recovered from the Eagle Butte Coal Mine about 48 miles north of here. It was found in the Tongue River Member of the Paleocene Fort Union Formation and is approximately 60 million years old. The Age of Reptiles was over and the Age of Mammals had begun. From small ancestors that survived the great Cretaceous extinction, giants would eventually evolve rivaling the dinosaurs in size and weight. This fossilized tree was a witness to this great change in Wyoming prehistory.

Wright, Wyoming · United States