There are few known fossil specimens of these ancient snakes and only three in which the hind limbs are preserved and visible.

这些古老蛇类的化石标本非常稀少，仅有的三个标本的后肢保存完好并可见。

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There are few known fossil specimens of these ancient snakes, and only three in which the hind limbs are preserved and visible.

有关这些古老蛇类的化石标本非常稀少，仅有的三个标本的后肢是加工过并且可见的。

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The University of Texas's digital library, known as Digimorph, for example, contains hundreds of specimens and nearly a terabyte of data.

例如，德克萨斯大学的被称做Digimorph的数字图书馆就包含几百种标本和接近1000G的数据资料。

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One of the new specimens, known as KMN-ER 62000, has a face like the type specimen of Homo rudolfensis (the fossil that defines the species, if species it turns out to be), though it seems to be from an adolescent, whereas the type specimen is an adult.

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These included well known naturalists such as Alfred Russel Wallace, who collected specimens in the Amazon and Malay Archipelago and independently formulated a theory of evolution by natural selection.

BBC: NEWS | Science/Nature | Darwin's letters archived on web