Colorado’s DeBeque Formation in the Piceance Basin preserves fossils from the transition between the Late Paleocene and Early Eocene, spanning the Clarkforkian to the Wasatchian in North American land mammal ages. Its importance rests on that fossil record, which has contributed to studies of early Eocene mammals, turtles, crocodilians, and fossil eggshell. Specimens from these rocks are represented in the University of Colorado Museum of Natural History. Together, these discoveries help document ancient environments and vertebrate life in western Colorado during a major period of change after the end of the age of dinosaurs.