Uncovered in south west China last year, Odontochelys semistestacea seems to be the oldest known turtle fossil – believed to date 220 million years back. More important it was used to put back the pieces regarding the evolution of the turtle shell.
Since long, paleontologists have been debating over the course of how the turtle developed its shell as some claimed that it evolved from underneath the body, while the other talked about it having been an extension of the scaly skin on top. And now we have the answer.
The uncovered fossil definitively supported the theory that the shell would have formed from below as extensions of the backbone and ribs, rather than as bony plates from the skin as others have theorized.
The fossil with its half formed lower shell and an absent upper shell proved the fact that it was the lower shell that first came into existence as a defensive mechanism of marine animals to protect themselves from attacks coming from the depths of the sea. As they started evolving as land creatures, the upper shell became an equally important form of defense and continued the evolution into its next step.
This also suggested to the team of scientists from Canada, China and the US who undertook this extensive research that the earliest turtles were indeed marine creatures and later moved onto land.