Phylogenetic reconstruction is the process by which biologists try to identify the evolutionary pathways which organisms have followed. The process is accomplished by examining the relationships between living and extinct organisms.With the advancement of mathematical, molecular, development, and cladistic techniques, the last ten years have seen radical changes in biologists' approaches to the problems of phylogenetic reconstruction with the advancement of mathematical, molecular, developmental, and cladistic techniques. Controversy has been abundant, and there has been a marked lack of integration of the various approaches. Views about the role of models have ranged from their being minimal to central to the process.This book examines models from a wide range of fields, at the same time providing illustrations of modern methods of classification and phylogeny reconstruction. As a result, information from development studies emerges as a significant factor in cladogram construction.