There are around 5,500 mammal species, among them our own. Although this has triggered a long history of research, the recent 15 years have seen rapid progress in disentangling the interrelationships and evolutionary history of particularly the placental mammals (which account for more than 90% of all living species). The present volume combines up-to-date reviews on mammalian phylogenetics with palaeontological, taxonomic and evolutionary chapters and also summarises the historical development of our insights in mammalian relationships (and thus our own place in the Tree of Life). In the light of the present biodiversity crisis, with one in four mammal species threatened by extinction, the distribution and conservation of mammal diversity across the globe is also given attention. The present volume is the introductory tome to the new Mammalia series of the Handbook of Zoology and will be essential reading for mammalogists, zoologists and conservationists alike.