At a time when natural history was a valuable tool for discovery, Merian discovered facts about plants and insects that were not previously known.

在那时，自然史是很有价值的探索工具，梅里安发现了有关植物和昆虫的真相，这些真相从未为人所知。

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The health district of Buea was not previously known to be a yellow fever endemic area.

以往并不清楚布埃亚卫生区属于黄热病流行地带。

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It was not previously known what ammonites fed on-and, in truth, this evidence applies only to the animal in question, a species of Baculites.

此前，鹦鹉螺的食性并不为人所知，事实样，这一证据只能证明一种存在疑问的物种- - -杆菊石的某一物种的食性。

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Mrs Falkingham did not live at the house and police said it was not previously known to them.

BBC: Nicole Falkingham

Two men have died in the Chinese city of Shanghai, after contracting a strain of bird flu not previously known in humans, Chinese officials say.

BBC: China bird flu: Two men die in Shanghai

The H7N9 strain was not previously known to infect humans before cases turned up in China this winter, and Zhong and other medical experts said no evidence exists that the virus can be passed from one person to another.

NPR: A New Case In China Adds Unknowns To Bird Flu