魚類の進化

Lampreys and hagfish belong to the Class: Agnatha(jawless bony fish). Subclass: Sarcopterygii(lobe finned fish) is diverged from Actinopterygii(ray finned fish) at Devonian era. Sharks, ray, skates belongs to subclass: Elasmobranchii. Class: Placodermi has been extinct. Paddlefishes, sturgeons, polydons are Chondrostei. Cartilageous fish has ampulae of Lorenzini in lateral line. Mauthner's cells and Müller cells have giant axons. Mauthner's cell is a pair large(100 m in goldfish) cell that coordinate muscle movement.