Odontochelys

Clad in hard, armoured shells, turtles have a unique body plan unlike that of any other animal. Their shells have clearly served them well and the basic structure has gone largely unchanged since the time of the dinosaurs. But this unchanging nature poses a problem for anyone trying to understand how they evolved and until now, fossil turtles haven't provided any clues. All of them, just like their living descendants, have fully formed two-part shells. But three stunning new fossils are very different. They belong to the oldest turtle ever discovered, which lived about 220 million years ago…