它还有一条细长的尾巴，这是哺乳动物的典型特征，今天的鲸鱼没有保留这一特征。

It also had a long thin tail, typical of mammals, something we don't see in today's whales.

youdao

关于返祖的一个有力例证就是人类的尾骨，它是哺乳动物尾巴的遗留物。

One striking example of an atavism is the human coccyx, or tailbone, which is a relic of the mammalian tail.

youdao

哺乳动物用它起平衡身体、传递信号和支撑物体的作用，尾巴在猿猴和人类中已经消失了。

Useful for mammals that use tails for balance, species-to-species signaling, and support, the tail is missing in apes and in humans.

youdao