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2000万年前的琥珀蜥蜴(英文)

更新时间:2015-7-28 19:33:13 来源:纽约时报中文网 作者:佚名

摘要:科学家在加勒比海域的小岛上收集到许多被琥珀包裹的古代安乐蜥化石。这些化石保存得精美完好,成了难得的研究材料。通过对比化石和岛上现存的安乐蜥,科学家发现这种蜥蜴历经千万年没怎么变样。

About 15 million to 20 million years ago, anoles were trapped in tree resin on what is now the island of Hispaniola, home to Haiti and the Dominican Republic.

Anoles still live in abundance on the island and throughout the Caribbean. Jonathan Losos, an evolutionary biologist at Harvard, has studied them for decades.

These lizards, as he has documented, occupy very specific bits of space on trees in rain forests. One species may live from the ground up to six feet high on the trunk, another species from six feet up the trunk to the crown, and another in the crown.

And although there are many different species on different islands, they fall into categories that characterize not only their behavior but their body structure. These forms — body types shaped by ecological niches — are called ecomorphs. The niches and the ecomorphs are the same in anole communities from island to island.

Dr. Losos was interested in finding out how long such communities have existed, so he turned to Hispaniola, famous for its amber — fossilized tree resin — in which insects and small creatures have been preserved.

With the help of colleagues and private collectors, he managed to gather 38 anoles in amber, all but one of the known such specimens in the world, all 15 million to 20 million years old and all from Hispaniola. About half came from a private collector in Italy.

With Emma Sherratt, a researcher in his laboratory, and other colleagues, they made micro CT scans of the 20 best specimens. Dr. Sherratt is now at the University of New England in Australia.

When they analyzed the body forms of the fossil anoles, they found the same categories that exist now. Dr. Losos said there was a great amount of discussion in evolutionary biology about whether ecological communities stay stable for long periods. It may not happen often, he said, but “our study does show that the same set of types of species can remain very static for long periods of time.”

It also shows a remarkable collection of amber and its captives, almost magical in the detail of their preservation. And although the preserved lizards have revealed valuable secrets, they remain puzzling in some ways. One anole, for instance, is preserved in great detail, except for its skeleton and internal organs, which for unknown reasons seem to have rotted away.

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