A team of palaeontologists have found the real reason why turtles developed a shell and it is not for protection as previously thought, but for burrowing underground where they sought shelter from the heat of Triassic South Africa.
The key piece of evidence came from a fossil of the oldest (260 million year-old) primitive turtle, Eunotosaurus africanus, that was discovered by 8 year-old Kobus Snyman on his father’s farm in Karoo, South Africa.
“Why the turtle shell evolved is a very Dr. Seuss-like question and the answer seems pretty obvious — it was for protection,” said Dr. Tyler Lyson, lead author of the research published by Current Biology.
Dr Lyson added: “Just like the bird feather did not initially evolve for flight, the earliest beginnings of the turtle shell was not for protection but rather for digging underground to escape the harsh South African environment where these early proto turtles lived.”
The paper shows that turtles evolved shells on land where it provided them with a stable base for a powerful digging mechanism.
“We knew from both the fossil record and observing how the turtle shell develops in modern turtles that one of the first major changes toward a shell was the broadening of the ribs,” said Dr. Lyson. “Ribs are generally pretty boring bones. The ribs of whales, snakes, dinosaurs, humans, and pretty much all other animals look the same. Turtles are the one exception, where they are highly modified to form the majority of the shell.”
“I want to thank Kobus Snyman and shake his hand because without Kobus both finding the specimen and taking it to his local museum, the Fransie Pienaar Museum in Prince Albert, this study would not have been possible,” said Dr. Lyson.