Johannesburg – A fossil discovery by an 8-year-old South African boy has helped scientists redefine why turtles have shells.While it has generally been accepted that the modern turtle shell is largely used for protection, a new study by an international group of scientists, including those from the Evolutionary Science Institute at Wits University, suggests the broad ribbed proto shell was initially an adaptation, not for protection, but rather for burrowing underground. The big breakthrough came with the discovery of several specimens, the oldest of which was a 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 studies' co-authors, Dr Roger Smith and Dr Bruce Rubidge from the University of Witwatersrand in Johannesburg but the most important specimen was found by 8-year-old Kobus Snyman on his father's farm in the Western Cape.This specimen, which is about 15cm long, comprises a well preserved skeleton together with the fully articulated hands and feet. Rubidge thanked Snyman saying he would "shake his hand" because without the finding the study would not have been possible.An artistic rendering shows an early proto turtle Eunotosaurus (foreground) burrowing into the banks of a dried-up pond to escape the harsh arid environment present 260 million years ago in South Africa. (Supplied, Andrey Atuchin) Puzzled scientistsLead author for the study, Dr Tyler Lyson of the Denver Museum of Nature and Science said that a shell for protection initially seemed like an obvious answer. "…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 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 towards a shell was the broadening of the ribs," said Lyson. While distinctly broadened ribs may not seem like a significant change, scientists say it has a serious impact on both breathing and speed in four-legged animals. Ribs are used to support the body during locomotion and play a crucial role in ventilating your lungs. Distinctly broadened ribs stiffen the torso, which shortens an animal's stride length and slows it down and interferes with breathing. 'Boring bones'"The integral role of ribs in both locomotion and breathing is likely why we don't see much variation in the shape of ribs," said Lyson. Lyson added: "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." The study included authors from the United States, South Africa and Switzerland.