The problem of the origin, differentiation, and relationships of living mammals has long been of great interest. Although some individuals have attempted to address the entire question, no one has been able to provide a complete synthesis. In recognition of this need, a based consortium was organized to provide a multifaceted, multidisciplinary attack on the problems of mammal phylogeny. Mammal Phylogeny brings together sixty distinguished researchers representing the fields of vertebrate paleontology, anthropology, mammal morphology, embryology, and molecular biology, resulting in 35 state-of-the-art papers addressing the current questions of this important field.