In the tradition of G. G. Simpson's classic work, Kenneth D. Rose's The Beginning of the Age of Mammals analyzes the events that occurred directly before and after the mysterious K-T boundary which so quickly thrust mammals from obscurity to planetary dominance.

Rose surveys the evolution of mammals, beginning with their origin from cynodont therapsids in the Mesozoic, contemporary with dinosaurs, through the early Cenozoic, with emphasis on the Paleocene and Eocene adaptive radiations of therian mammals. Focusing on the fossil record, he presents the anatomical evidence used to interpret behavior and phylogenetic relationships. The life's work of one of the most knowledgeable researchers in the field, this richly illustrated, magisterial book combines sound scientific principles and meticulous research and belongs on the shelf of every paleontologist and mammalogist.