原文是it is like finding a mouse the size of a cow. 其实译文不准确。我的理解是指发现的这种恐龙比同属的窃蛋龙大了好多倍. 几乎相当于牛和鼠的对比。直译：就像发现了一只和牛一样大的老鼠。
附上相关前后文就清楚了
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巨盗龙于2007年在戈壁滩上被发现
Gigantoraptor was discovered in 2007 in the Gobi Desert of Mongolia.
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它骨骼的尺寸
The sheer size of the bones
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足以说明它的与众不同
revealed it was unlike anything found before -
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体长八米 重约一点五吨
eight metres long and weighing around 1.5 tonnes.
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从它的骨骼我们知道
From its bones, we know
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它比同属的窃蛋龙大了三十五倍
it was 35 times bigger than its closest Oviraptorid relatives.
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但是这庞然大物还没有成长完全
And yet this giant wasn't even fully grown.
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有点"以为鼠小 鼠比牛大"的意思
it was "like finding a mouse the size of a cow".
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