在非洲、美洲和澳大利亚的江河里，生长着一种介于鱼类和两栖类之间的珍奇动物，它叫肺鱼。肺鱼出现于４亿年前的泥盆纪时期，它身上披着瓦状的鳞，背鳍、臀鳍和尾鳍都连在一起，并有构造最古老的“原鳍”，所谓原鳍与正常鱼鳍不同之处是一个肉柄状的东西。肺鱼的鳔的构造很像 In the rivers of Africa, the Americas, and Australia, there is an exotic animal that lives between fish and amphibians. It is called lungfish. The lungfish appeared in the Devonian period 400 million years ago. The body was covered with tile-like scales. The dorsal, anal, and caudal fins were connected together, and the oldest “former fins” were constructed. The so-called primary fins and normal fish were found. The fin is different from a meat handle. The structure of the lungs of the lungfish is very similar