Mutant zebrafish with extra fin bones may hold clues to how the first animals walked on land

Almost 700 years ago, a Dutch naturalist envisioned a fish with arms that would enable it to climb out of the water, setting the stage for terrestrial life. Now, it turns out, his fantasy had roots in reality. Researchers studying skeletons of the finger-size zebrafish have discovered mutants that grow extra bones in their front fins.

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