In the Guizhou Province of southwestern China, Chun Li of the Chinese Academy of Sciences, has found a new fossil that may help explain the evolution of the turtle. The oldest known turtle species is from 210 million years ago and features a full top shell , called a carapice, and a bottom shell, called a plastron. The new fossil, named Odontochelys semistestacea, lived 10 million years earlier and has only a full bottom shell. The top shell is incomplete, with only bony extensions from the back bone and ribs.
Scientist used to think that a turtle shell evolved from scales that formed plates, which then fused into a shell. This new fossil evidence tells a different story of a shell forming from changes to the animals skeleton.