... 早白垩纪 gault series 第三纪 [地质学] (新生代第一个纪) tertiary; the tertiary period 白垩纪的化石 cretaceous fossils ...
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这个有着6550万年历史的地层分离了白垩纪的化石和第三纪的化石。
This 65.5-million-year-old layer of Earth separates fossils of the Cretaceous period from those of the Tertiary period.
但是很不幸的是，这段迅速的进化过程发生于中白垩纪的一千五百万年间，而这段时期的鲜有化石记录。
"But there were a hundred million years of evolution to play with."
在犹他州和阿拉斯加州还发现了另一种鸟的“足迹”化石，但都无法追溯到白垩纪早期——恐龙时代的鼎盛时期。
Other bird "trace" fossils have been found in Utah and Alaska, but none from so far back as the early Cretaceous -- at the height of the age of dinosaurs.
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