Editor's Summary
10 July 2008
Evolution: How flatfish see eye-to-eye
The asymmetry of flatfish is an exceptional morphological specialization that arises in development: starting from a symmetrical larva/juvenile, the skull is remodelled so that one eye migrates over the top of the skull to sit next to its fellow on one (or other) side of the animal. The evolutionary origins of this arrangement have been unclear. Matt Friedman re-examined Eocene (47-million-year-old) fossils of the fish Amphistium and describes a new genus that represents the most primitive flatfish known. In these fish, the migrating eye never gets further than the dorsal midline, even in fully adult fishes. This is a graphic example of a transitional form spotted in the fossil record, confirming that the evolution of the specialized flatfish bodyplan was a gradual process.
News and Views: Palaeontology: Squint of the fossil flatfish
Evolutionary biologists have floundered when trying to explain how the asymmetrical head of flatfishes came about. 'Gradually' is the answer arising from exquisite studies of 45-million-year-old fossil specimens.
Philippe Janvier
doi:10.1038/454169a
Letter: The evolutionary origin of flatfish asymmetry
Matt Friedman
doi:10.1038/nature07108
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