This edited volume explores the various views on the origins of tetrapods-amphibians, reptiles, birds, and mammals-views that agree or differ depending in part on how certain fossil animals are classified and which methodology is used for classification. Eighteen chapters by an international group of paleontologists and neontologists here present current hypotheses, emphasizing the kinds of data needed to answer controversial questions, as well as the variety of solutions that emerge from diferent analyses of the same data set. The book is arranged in five sections, each of which contains an overview essay that either describes the development of various schools of thought regarding the origin of the tetrapod group in question or critically summarizes the arguments presented in the section. The first section addresses the origins of tetrapods as a group, focusing on lobe-finned fishes and early tetrapods. Next is a section dealing with amphbians, followed by one on reptiles. The fourth section concerns avian origins, and the final section treats the origins and early diversification of mammals. With an overall goal of stimulating critical evaluation by the reader rather than providing unequivocal answers, this volume will be of particaular interest to vertebrate paleontologists, evolutionary morphologists, and ichthyological, herpatological, avian, and mammalian systematists.