Carl Zimmer on a curious case involving fins about 375 million years ago.
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Tiktaalik’s importance came into sharp focus when scientists put it on an evolutionary tree along with land vertebrates — known as tetrapods — and other tetrapod-like fish. By looking at these branches, scientists could see how the tetrapod body evolved, step by step. Fish first evolved the long bones in their legs, later adding wrists and ankles. Later still, fingers and toes arose.
Now, Dr. Shubin and his colleagues have added yet another branch to our evolutionary tree with a fossil that they unknowingly discovered in Nunavut, even before finding Tiktaalik.
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