Proto Turtle Shells Initially for Burrowing Underground Not Protection

The early evolution of the turtle shell had long puzzled scientists. “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.

A recent study on the oldest proto turtle, Eunotosaurus (left), suggests the broadening of the ribs in turtles was initially an adaptation for burrowing to escape the extremely arid environment of South Africa 260 million years ago. Later the ribs were incorporated into the modern protective turtle shell as found in Pelusios (right).

Credit: Luke Norton

This is a new fossil of the oldest proto turtle, Eunotosaurus, discovered by then 8-year-old Kobus Snyman on his father’s farm in the Karoo of South Africa suggest the turtle shell initially evolved not for protection, but rather as an adaptation for burrowing. The broadened ribs and the beginnings of the turtle shell provided Eunotosaurus with a stable base from which it could use its large hands and spatula shaped claws to burrow into the ground to escape the harsh arid environment found in South Africa 260 million years ago. 

Credit: Tyler R. Lyson 

A big breakthrough came with the discovery of several specimens of the oldest (260- million-year-old) partially shelled proto turtle, Eunotosaurus africanus, from the Karoo Basin of South Africa. Several of these specimens were discovered by two of the study’s coauthors, Drs. Roger Smith and Bruce Rubidge from the University of Witwatersrand in Johannesburg. But the most important specimen was found by a then 8-year-old South African boy on his father’s farm in the Western Cape of South Africa. This specimen, which is about 15 cm long, comprises a well preserved skeleton together with the fully articulated hands and feet.

“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.

The study includes authors from the United States, South Africa, and Switzerland.