巴基鲸可能是通过像陆地哺乳动物一样的耳朵的开口来探测声音。
Pakicetus probably detected sound through the ear opening as in land mammals.
直到最近才发现的化石，显然是介于陆地哺乳动物和鲸类之间的过渡物种。
Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.
叉角羚与羚羊虽无亲缘关系，但却形似羚羊，它是新大陆速度最快的陆地哺乳动物。
The pronghorn, which resembles an antelope, though they are unrelated, is the fastest land mammal of the New World.
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