在人类出现很早以前，地球上就出现了鱼类、爬虫类、鸟类和一些哺乳动物。

Long before Man lived on the Earth, there were fishes, reptiles, birds, insects, and some mammals.

youdao

在人类出现很早以前，地球上就出现了鱼类、爬虫类、鸟类和一些哺乳动物。

Long before Man lived on the Earth, there were fishes, reptiles, birds, insects, and some mammals.

youdao