The Proboscidea, of which only two species of elephant survive today, were one of the great mammalian orders of the Cenozoic. Their success over evolutionary time is reflected by their morphological and taxonomic diversity, their nearly worldwide distribution on every continent except Australia and Antarctica, and their persistence through nearly fifty million years. Their great past ability to migrate and to adapt to changing climatic conditions and interspecific competition provides a unique laboratory for the testing of evolutionary theories and development of new concepts. This is the first complete treatise on the evolution and palaeoecology of this group for half a century. It reviews their classification and phylogeny, the early differentiation of proboscideans, the major adaptive radiations and their evolutionary patterns, and the origins and current status of extant elephant species. Written by leading international experts, this is a major study documenting the record of terrestrial biodiversity.