About the book: The Osteichthyes, including bony fishes and tetrapods, is a highly speciose group of animals, comprising more than 42000 living species. The extraordinary taxonomic diversity of osteichthyans is associated with a remarkable variety of morphological features and adaptations to very different habitats, from deep-sea to high mountains. The osteichthyans thus provide an interesting case study to analyze the origin and morphological macroevolution of higher clades. This book provides a new insight on the osteology, myology, phylogeny and evolution of this fascinating group. Chapters 1 and 2 provide a short introduction to the main aims of the book and to the methodology used. Chapter 3 deals with an extensive cladistic analysis of osteichthyan higher-level interrelationships based on a phylogenetic comparison of 356 characters in 80 extant and fossil terminal taxa representing all major groups of Osteichthyes. This cladistic analysis includes various terminal taxa and osteological characters, and principally a large number of myological characters, not included in previous analyses. Chapter 4 provides a general discussion on issues such as the comparative anatomy, homologies and evolution of osteichthyan cranial and pectoral muscles, the development of the cephalic muscles of Vertebrates and the implications for evolutionary developmental biology ("evo-devo"), the origin, homologies and evolution of one of the most peculiar and enigmatic structural complexes of osteichthyans, the Weberian apparatus, and the use of myological versus osteological characters in phylogenetic reconstructions. It is hoped that the data presented in this book may stimulate, and pave the way for, future studies on the comparative anatomy, functional morphology, phylogeny and evolution of osteichthyans and of Vertebrates in general.