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Primitive fish may shed light on evolution of limbs

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Living fossil

The coelacanth was once thought to have gone extinct about 70 million years ago, roughly around the time dinosaurs vanished. But in 1938, a fish trawler brought a bluish-purple, 3.3-foot-long (1 meter) fish with fleshy fins to the South African naturalist Marjorie Courtenay-Latimer. It turned out to be an African coelacanth.

Over the next several decades, scientists unearthed a few hundred of the elusive creatures living around the Comoros Islands in the Indian Ocean, as well as off parts of Indonesia.

The coelacanth intrigued scientists because it was a kind of "living fossil": It had changed so little over the last 400 million years that it might reveal how fish first grew limbs and walked on land.

Deepening the mystery, other research showed that fish, mice and other animals carry many of the same genes. But in fish, those genes code for fins, whereas in land-based animals, they create limbs.

Mysterious genes

Because the fish were so endangered, it was difficult to study their body plan in detail. But Amemiya and his colleagues managed to get tissue samples from a coelacanth from the Comoros Islands.

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