Previous Next / The Crazy Mountains Basin Project of south-central Montana is focused on elucidating the diversification of mammals during the Paleocene epoch The Crazy Mountains Basin (CMB) Project, initiated in 1982 and now a large collaborative project involving researchers at several institutions, is designed to document a major transition in mammalian faunas not long after the end-Cretaceous mass extinction. In the 10 million years following the extinction, during the Paleocene epoch (ca. 65–55 million years ago), mammals underwent a major diversification and became dominant land animals. However, despite the fact that almost one half of the known orders of Cenozoic mammals arose in the Paleocene, less is known about the composition and diversity of mammalian faunas during this time than during any of the later epochs of the so-called Age of Mammals. A large-scale turnover in mammalian faunas, among the most dramatic during the Early Cenozoic, occurred near the middle of the Paleocene epoch. The Crazy Mountains Basin of south-central Montana contains the best-known sequence of mammals documenting this transition.