Children learn that turtles have a protective shell, which is like a mobile home for them. It protects them from the predators and makes them really tough. However, a new study from the University of Zurich revealed that this shell evolved not to make turtle able to protect itself, but to allow animal digging more effectively.
The shell of the turtle evolved as the ribs widened and grew together. Now it serves a protective function – as turtle withdraws into its shell, it becomes virtually indestructible rock and most of the predators have to walk away. However, scientists were puzzled for a long time, why and how did the turtle evolve this shell. Fossils and modern day turtle analysis show that evolution took place as ribs got wider and wider. However, ribs do not have a function of protecting the animal – they protect the lungs and allow for ventilation. Broadening of the ribs is not very good, because animal becomes slower and cannot breathe as effectively.
In fact, the form follows the function when it comes to ribs and virtually all animals have ribs of the same shape. However, turtles are much different, as their ribs evolved into a protective shell. Now scientists think they made a breakthrough, by analysing several examples of the oldest, 260-million-year-old proto-turtle Eunotosaurus africanus. It lived in South Africa and only had a partially developed shell. Many of these examples were collected during expeditions and some, very important ones, were discovered by accident by local people.
One specimen, found by a local eight-year-old boy in Karoo Basin, has a well-preserved skeleton, including all four feet. Scientists examined broadened, spade-shaped fingers, which were meant for digging. They also noticed that broadened ribs served the purpose of supporting the front legs. Torsten Scheyer, one of the palaeontologists of the research, said: “The proto-shell enabled the animals to burrow into the ground and brave South Africa’s inhospitable environmental conditions in subterranean dens”.
There is still a lot to find out about Earth’s wildlife. Evolution took unexpected turns and we can only imagine what else will be uncovered in the near future.