What light do fossils shed on the deep history of life's most diverse phylum, the Arthropoda? Are the interrelationships between major groups of arthropods—crustaceans, chelicerates, and tracheates—resolved the same way whether or not fossils are included? How should we combine evidence from extinct and extant taxa? These are the central questions of Many recent controversies in arthropod evolution have been initiated by new fossil discoveries and new interpretations of early fossils. This book examines the role that these finds and ideas have played in understanding the deep evolutionary history of arthropods. The authors of the book's seven chapters have been at the forefront of this research. Contributions include phylogeny based on DNA sequence data for living groups, cladistic analysis of the major lineages of arthropods, detailed case studies of crustaceans, chelicerates, and lobopodians, and the evolutionary significance of arthropods in Cambrian fossil sites with exceptional preservation. All contributors use cladistic methods, presenting copious new data to stimulate further research. The book will be a vital resource for paleontologists, researchers on extant arthropods interested in fossil history, and evolutionists concerned with how different kinds of systematic data should be analyzed.