This book presents current knowledge of the early vertebrates--mainly fish, but including some terrestrial creatures--which lived about 250 to 470 million years ago. The work focuses on anatomical and phylogenetic questions, but includes information on fossil discovery and preparation, as well as the analysis of the characteristics from which their relationships may be reconstructed. The author addresses both new and old problems in the evolution of certain anatomical details and deals briefly with the animals' way of life, extinction, and former distribution. The book is the first in its field to use a cladistic approach. For each major vertebrate group, the reader will find a diagram of relationships, or cladogram, with a selection of characters at each node, and a succinct phylogenetic classification.