The Real Reason Turtles Have Shells

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Source Azula by  Rachel Kaufman 

HINT: It is Not For Show.  The turtle is unique in the animal kingdom for its shell, which is actually a modified rib cage made up of 50 bones. No other living vertebrate has anything like it.

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The shell gives turtles super defenses against predators — even more so because most turtles can pull their heads and legs into their shell, becoming an even more impenetrable fortress.

But new research has discovered that turtles did not originally use their shells for protection. Rather, early turtles probably evolved their shells to help them dig.

Researchers made the discovery after an 8-year-old boy found some fossilized bones on his father’s farm in South Africa.

Turtle Fossil - Photo Credit: Tyler R. Lyson

He took the bones to a local museum, where researchers determined it was the most complete skeleton ofEunotosaurus africanus, an early turtle-like creature (known as a “stem turtle”) that lived 260 million years ago. (It may have looked like this.)

Eunotosaurus Africanus - Photo Credit: Wikimedia Commons, Smokeybjb

By studying this and other Eunotosaurus remains, scientists were able to puzzle out something that has long flummoxed paleontologists.

One of the first evolutionary changes toward turtledom is a broadening of the ribs, which doesn’t sound like much, but really affects how an animal moves and lives, the scientists said. Distinctly broadened ribs make for a stiffer torso, which slows an animal down and also makes it harder to breathe.

Eunotosaurus wasn’t thought to have a shell, but it had these broadened ribs. So what gives?

Turns out, the scientists said, this species of stem turtle liked to dig. “The broad ribs provide an intrinsically stable base” to give Eunotosaurus more leverage for a strong digging pair of front legs, the scientists said in a paper in Current Biology.

The turtle ancestor probably dug burrows to escape the hot African sun.

The powerful digging legs likely helped turtles when they started to move to the water, since those digging legs then became swimming legs.

Just goes to show that even the humble turtle has more to teach us.

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August 31, 2016 |

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