始祖鸟开闢了脊椎动物生活在空中的大道我们知道,动物界包括有两大类,一类是无脊椎动物,一类是脊椎动物。前者是没有脊椎的比较低级的动物,后者是具有脊椎的高级的动物。我们人类当然是属于高级的脊椎动物的范围了。但是日常所见到的鸟类像乌鸦、麻雀、鹰鹫、斑鸠等也同样是脊椎动物,而且还是一种很繁盛的重要的脊椎动物呢。这些岛类可以划过长空自由的飞翔,可以盘旋高空,也可以俯冲低览,生活得自由自在,活泼愉快。因此古代的人最是羡慕他们,常有“插翅而飞”的幻想。但是鸟类所以能自由飞翔,是靠了什么呢?当然是靠了它的两个翅膀。这是极简单的事实,小孩子都会毫不迟疑地讲出来的。可是最最初这两双翅膀是怎样生成的,却不是个简单的问题,而是经过一个 The Archaeopteryx has opened up the vertebrates that live in the air. We know that the animal kingdom includes two major categories, one is invertebrates and the other is vertebrates. The former is a relatively low-grade animal without a spine, and the latter is a superior animal with a spine. We humans of course belong to the range of advanced vertebrates. But the birds that we see daily are like crows, sparrows, hawksbills, and doves. They are also vertebrates, and they are a very important and important vertebrate. These islands can fly freely through the sky and can hover above the air, or they can dive in and out, and live freely and lively and happy. Therefore, people in ancient times were most envious of them. They often had the illusion of “winging and flying.” But what is it that the birds can fly freely? Of course, it depends on its two wings. This is a very simple fact, and children will not hesitate to say it. However, the first two pairs of wings were generated, but it was not a simple problem, but a passing one.