地球上的鱼类大约有2万多种,如何将它们分门别类地区别开来,这既是一个包含生物分类科学的严谨工作,又是一个引人入胜的话题。我们知道,现代分类学上(包括对鱼的分类)采用的等级主要有门、纲、目、科、属、种,必要时还可 There are about 20,000 species of fish on the earth, how to separate them into different categories, which is both a rigorous work that contains the science of taxonomy and is also a fascinating topic. We know that the modern taxonomic (including the classification of fish) used in the main levels of door, class, head, branch, genus, species, if necessary, but also