CHICAGO (Reuters) - Some odd-looking fish fossils discovered in the bowels of several European museums may help solve a lingering question about evolutionary theory, U.S. researchers said on Wednesday.
The 50 million-year-old fossils -- which have one eye near the top of their heads -- help explain how flatfish such as flounder, sole and halibut developed the strange but useful trait of having both eyes on one side.
For flatfish, which lie on their sides at the bottom of the sea, this arrangement gives them the use of two watchful eyes.
But the trait has posed a problem for evolutionary biologists because no one had found any so-called transitional fossils -- fossils showing intermediate steps in the evolution of this trait.
"The important thing about this study is it delivers evidence of those intermediates," said Matt Friedman of The Field Museum and the University of Chicago, whose study appears in the journal Nature.
This missing link in the evolution of flatfishes has been seen as a hole in the theory of natural selection.
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