Turtle
The earliest turtle fossils come from Upper Triassic of the Mesozoic era, about 220 million years ago. Their shell evolved from bony extensions of their backbones and broad ribs that became larger and grew together to make a complete shell. This adaptation was very useful and has been around for a long time. It helped protect turtles as they evolved over many years, even when the bony part of the shell was not complete. The group as a whole has survived many changes in the seas and several extinction events.