1 Introduction. - 1. 1. Conspectus 1; 1. 2. Evolution of jaws 2; 1. 3. Fossil record 4; 1. 4. Environment 6; 1. 5. Classification 7; References 8; Bibliography 9. - 2 Class Cephalaspidomorphi. - 2. 1. Classification 10; 2. 2. Cephalaspidomorph characteristics 11; 2. 3. Infraclass 1 Osteostraci 12; 2. 3. 1. Structure 13; 2. 3. 2. Growth and life history 19; 2. 3. 3. Diversity and tendencies in evolution 20; 2. 4. Infraclass 2 Anaspida 23; 2. 4. 1 Structure 24; 2. 4. 2. Growth 26; 2. 4. 3. Diversity 27; 2. 5. Infraclass 3 Petromyzonida 27; 2. 5. 1. Structure 27; 2. 6. Incertae sedis Palaeospondylus 28; 2. 7. Mode of life 29; References 31. - 3 Class Pteraspidomorphi. - 3. 1. Classification 35; 3. 2. Pteraspidomorph characteristics 36; 3. 3. Subclass 1 Heterostraci 36; 3. 3. 1. Structure 36; 3. 3. 2. Growth and the evolution of the shield 41; 3. 3. 3. Diversity and interrelationships 45; 3. 3. 4. Mode of life 49; 3. 4. Incertae sedis Polybranchiaspis 52; 3. 5. Subclass 2 Thelodonti 53; 3. 5. 1. Structure 53; 3. 5. 2. Diversity and affinities 55; 3. 6. Relationships of agnathans 56; References 57. - 4 Subclass Acanthodii. - 4. 1. Classification 61; 4. 2. Acanthodian characteristics 61; 4. 2. 1. Structure 63; 4. 2. 2. Diversity and tendencies in evolution 71; 4. 2. 3. Mode of life 75; References 76. - 5 Subclass Osteichthyes. Infraclass Actinopterygii. - 5. 1. Classification 79; 5. 2. Osteichthyan characteristics 80; 5. 3. Infraclass Actinopterygii 81; 5. 4. Superorder 1 Chondrostei 86; 5. 5. Order 1 Palaeoniscida 86; 5. 5. 1. Structure 87; 5. 5. 2. Suborder 1 Palaeoniscoidei 91; 5. 5. 3. Suborder 2 Platysomidei 94; 5. 6. Order 2 Haplolepidida 97; 5. 7. Order 3 Tarrasiida 97; 5. 8. Order 4 Phanerorhynchida 98; 5. 9. Order 5 Dorypterida 99; 5. 10. Superorder 2 Holostei 99; 5. 11. Order 1 Semionotida 100; 5. 12. Tendencies in evolution 102; References 105. - 6 Subclass Osteichthyes. Infraclass Crossopterygii. - 6. 1. Classification 110; 6. 2. Crossopterygian characteristics 111; 6. 3. Superorder 1 Rhipidistia 113; 6. 3. 1. Structure 114;6. 3. 2. Order 1 Holoptychiida 122; 6. 3. 3. Order 2 Osteolepidida 125; 6. 3. 4. Order 3 Rhizodontida 126; 6. 3. 5. Tendencies in evolution 127; 6. 4. Superorder 2 Actinistia 127; 6. 4. 1. Structure 127; 6. 4. 2. Diversity 131; 6. 5. Incertae sedis Onychodontidae 131; 6. 6. Mode of life 134; References 136. - 7 Subclass Osteichthyes. Infraclass Dipnoi. - 7. 1. Classification 141; 7. 2. Dipnoan characteristics 141; 7. 3. Structure and diversity 144; 7. 3. 1. Structure 144; 7. 3. 2. Diversity 149; 7. 4. Evolution and mode of life 153; 7. 5. Growth of cosmoid scales and bones 154; 7. 6. R elationships of teleostomes 155; References 158. - 8 Subclass Placodermi. - 8. 1. Classification 161; 8. 2. Placoderm characteristics 162; 8. 3. Order 1 Arthrodira 163; 8. 3. 1. Structure 164; 8. 3. 2. Diversity and tendencies in evolution 170; 8. 4. Order 2 Ptyctodontida 178; 8. 5. Order 3 Phyllolepidida 180; 8. 6. Order 4 Petalichthyida 181; 8. 7. Order 5 Rhenanida 185; 8. 7. 1. Suborder 1 Palaeacanthaspidoidei 185; 8. 7. 2. Suborder 2 Gemuendinoidei 188; 8. 8. Order 6 Antiarchi 191; 8. 9. Incertae sedis Stensioellidae 195; 8. 10 Evolution and mode of life 197; References 200. - 9 Subclass Chondrichthyes. Infraclass Elasmobranchii. - 9. 1. Classification 206; 9. 2. Chondrichthyan characteristics 206; 9. 3. Infraclass Elasmobranchii 209; 9. 4. Order 1 Cladoselachida 210; 9. 5. Order 2 Cladodontida 213; 9. 6. Order 3 Selachii 215; 9. 6. 1. Suborder 1 Ctenacanthoidei 215; 9. 6. 2. Suborder 2 Hybodontoidei 217; 9. 7. Order 4 Xenacanthida 218; 9. 8. Incertae sedis Order 5 Helicopriondia 220; 9. 9. Evolution 221; 9. 10. Mode of life 222; References 223. - 10 Subclass Chondrichthyes. Infraclass Holocephali. - 10. 1. Classification 226; 10. 2. Holocephalan characteristics 227; 10. 3. Order 1 Chimaerida 229; 10. 3. 1. Suborder 1 Helodontoidei 229; 10. 3. 2. Suborder 2 Cochliodontoidei 231; 10. 3. 3. Suborder 3 Menaspoidei 231; 10. 4. Order 2 Chondrenchelyida 233; 10. 5. Order 3 Edestida 234; 10. 6. Incertae sedis Ornithoprion 237; 10. 7. Order 4 Psammodontida 238; 10. 8. Order 5 Copodontida 238; 10. 9. Incertae sedis Order 6 Petalodontida 239; 10. 10 Evolution and mode of life 240; 10. 11. Relationship of elasmobranchiomorphs 242;References 244. - 11 Summary of the early evolution of fishes. Language: English