鱼类是地球上最早出现的脊椎动物,大约在4亿年前的古生代志留纪,在占地球面积70%以上的茫茫大海中已经有了原始鱼类。经过千万年的发生和分化,到了泥盆纪,鱼类已发展成为地球上主要的动物群,被称为“鱼类的时代”。现代硬骨鱼类的祖先——古鳕(Palaeoniscids),就出现在那个时代。但在漫长的历史时期中,地球上发生过多次剧烈的造山移海运动,使许多古生代鱼类因海洋环境的巨变,有些早已绝迹;有些则受环 Fish is the earliest vertebrate on earth, about 400 million years ago, the Paleozoic Silurian, in the vast oceans accounted for more than 70% of the ocean already have the original fish. After thousands of years of occurrence and differentiation, up to the Devonian period, the fish have evolved into the major fauna on Earth, known as the “era of fish.” The ancestor of modern bony fish, Palaeoniscids, appeared in those days. However, during the long historical period, there have been many violent orogeny and sea movement on Earth. Many Paleozoic fishes have long been extinct due to the great changes of the marine environment. Some of them have long been extinct.