四足动物的脖子通常很长，这样它们就可以毫不费力地够到食物，但是大象的脖子很短，这样它就可以更容易地支撑它巨大的头和沉重的牙齿的重量。
The neck of four footed animals is usually long, to have them reach their food without difficulty, but the elephant has a short neck, to make him more easily support the weight of his huge head and heavy teeth.
我们读了一封关于一些四足动物的髓质脊髓的信。
We read a letter about the medulla spinalis of some quadrupeds.
由塔丰·奥兹利克带领的土耳其科学家提出，一个基因的突变可能会导致四足动物的出现。
Turkish scientists led by Tayfun Ozcelik suggested that a mutation in a single gene might result in quadrupedalism.
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