Among Earth's creatures, turtles are the only animals to form a shell on the outside of their bodies through a fusion of modified ribs, vertebrae and shoulder girdle bones.
The turtle shell is a unique modification, and how and when it originated has fascinated and confounded biologists for more than two centuries. A Smithsonian scientist and colleagues recently discovered that the beginnings of the turtle shell started 40 million years earlier than previously thought. The team's research is published in the May 30 issue of Current Biology
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