迷齿类 迷齿构造原总 始鳍 Labyrinthodont 两鱼 总鳍鱼类 Opercular bones 栖类的比较 鱼类 P Circumorbital bones 两栖类 avity Tooth-bearing bones 一类肉鳍鱼亚纲与 Figure 12-33 Similarity between the crossopterygians phibian(right); shading identifies the bones(u= ulna, r and the earliest amphibians. a. Similanity of skeleton. b. radius, h= humerus) that the two groups have in common mparison of skulls and lower jaws of a crossopterygian d, Comparison of cross sections of showing the com- (left) and an ichthyostegid amphibian(right). Shading identi- plex structure found in both the crossopterygians(left)and fies the bones the two skulls have in common. c Compari- amphibians(right) son of the limb bones of a crossopterygian(left) and am-总鳍鱼类( 肉鳍鱼亚纲) 与 原始两栖类的比较 迷齿类 总鳍鱼类 迷齿构造 鱼类 两栖类