If you ask most people to guess why turtles first developed shells, you’ll usually get one answer: the hard shells protect them from predators. That’s the theory scientists have been working with for decades, however a new study suggests everything we know about the evolution of the turtle is probably wrong — and it’s all thanks to a fossil discovered by one 8-year-old boy from South Africa.
The study examines the remains of 47 different ancient proto-turtles from a species called Eunotosaurus africanus which had developed partial shells. One fossil in particular helped crack the case: a 6-inch-long specimen uncovered by 8-year-old Kobus Snyman. Compared to the other fossils in the collection, this 260-million-year-old specimen was remarkably complete, containing almost all of the skeleton, as well as the hands and feet of the ancient reptile.
After discovering the fossil, the boy immediately turned it over to his local museum in Prince Albert, South Africa. It was this discovery that allowed scientists from the Denver Museum of Nature and Science to finally understand the purpose of the proto-turtle’s broadened ribs and stiffened torso. It wasn’t for protection, as first thought: rather, these reptiles developed partial shells in order to more easily burrow underground. The modified ribcage gave these creatures a more stable base when digging.
This explains one of the most enduring questions that’s puzzled researchers for decades: why would turtles evolve shells in the first place? While it’s true they offer protection, they also make the turtle much slower and make it more difficult for the animals to breathe. Most other species on the planet have maintained narrower, more flexible ribs for exactly these reasons. Now that scientists know the early versions of shells served a very specific purpose, the adaptation makes more sense. The full finding have been published in the journal Current Biology.
Images via the Denver Museum of Nature and Science