科学家将白垩纪末期的大灭绝与地球上的陨石撞击联系起来。
Scientists have linked the mass extinction at the end of the Cretaceous with a meteorite impact on Earth.
在他看来，在白垩纪虱子物种进化时的宿主可能是哺乳动物系统树上的另一分支而这一分支上的所有物种都灭绝了。
In his view, the hosts on which lice were speciating during the Cretaceous could have been a different branch of the mammalian family tree, all of whose species are extinct.
它说明了虱子的历史非常久，在白垩纪-早第三纪过渡期之前，而且也肯定是寄生在某种生物上的。
It says lice are old, predate the Cretaceous-Paleogene boundary, and must have been living on something.
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