Boundary clay layers are used by scientists to determine the rate at which an extinct species declined.

边界粘土层被科学家用来确定一个灭绝物种衰落的速度。

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An extinct species or race of human beings, Homo neanderthalensis, associated with Middle Paleolithic tools.

作为已灭绝物种或人类种族，尼安德特人与旧石器时代中期的工具有关。

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A technology used to develop new medical treatments might one day revive endangered or extinct species.

科学技术常常能带来新的医学疗法，有一天这些新疗法可能会拯救濒危物种，甚至重现灭绝的物种。

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Until two years ago, the Red List of Threatened Species of the World Conservation Union said Przewalski's horses were extinct in the wild.

VOA: special.2010.06.22

"A citizen scientist outside Peoria actually sent in a photograph of a species of bumblebee, the rusty patched bumblebee,bombus affinis, that was thought to have gone extinct in that area, and was recovered by a private citizen with a digital camera."

VOA: special.2011.05.24

But for these vigorous conservation measures, the unlimited-liability names might well be an extinct species already.

ECONOMIST: The Lloyd's insurance market

"Good news has become a near-extinct species, " said Bruno Giussani, European director of TED at the opening of the conference.

BBC: 'Virtual human' Milo comes out to play at TED in Oxford

But the anatomical modifications which show biologists that these extinct species were not the world's greatest aviators, also serve to obscure their origins.

ECONOMIST: Feathers are flying in the world of bird classification