You won't ever find feathers on a mammal or gills on a primate.
你在哺乳动物身上找不到羽毛，在灵长类动物身上找不到腮。
The new study found that 70 percent of rodent and primate groups have species with an appendix.
这项新的研究发现，70%的啮齿动物和灵长类动物的物种具有阑尾。
Others, such as extra-long forearms and flexible feet, date from deeper in the primate past.
其它特征，如超长前臂和灵活的脚，则可追溯更远灵长类动物的过去。
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