始祖兽（学名Eomaia）是一种已灭绝的哺乳动物，有可能是真兽下纲的最早祖先。始祖兽的化石是在中国辽宁的义县组发现，可追溯至下白垩纪的巴列姆阶。这个标本长10厘米及差不多完整，估计重量为20-25克。这个化石完好的保存了1亿2500万年。虽然头颅骨被埋扁，但它的牙齿、脚骨、软骨及其毛皮都可以看见。
这种反对是合理的，因为只有早期的兽脚亚目食肉恐龙的锁骨才被发现，但是现在已经发掘出了类似始祖鸟的叉骨的兽脚亚目食肉恐龙锁骨化石。
This objection was reasonable when only early theropod clavicles had been discovered, but fossilized theropod clavicles that look just like the wishbone of Archaeopteryx have now been unearthed.
可能已经是时候最终接受‘始祖鸟’只是又一只在侏罗纪时期飞来飞去的长有羽毛的像鸟类的小兽脚亚目食肉恐龙了。
Perhaps the time has come to finally accept that archaeopteryx was just another small, feathered, bird-like theropod fluttering around in the Jurassic.
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