How The Turtle Got Its Shell
The Indian Star Tortoise Wikimedia Commons Pictured: a turtle with a really cool shell. The turtle shell isn't like any other protective element of any living animal: it's not an exoskeleton, like some invertebrates have, nor is it made of ossified scales like armadillos, pangolins, or some snake and reptile species. It's not made of skin. It can't be removed--to do so would kill the turtle, and all that's underneath is internal organs. So how did this very common animal end up so unique? New research from Tyler Lyson at Yale University furthers an existing theory: that turtles stem from a 200-million-year-old dinosaur called Eunotosaurus. Eunotosaurus looks sort of like a cross between a turtle and a lizard, or like a lizard that's somehow swallowed a cannonball: The turtle shell is actually a peculiar evolution of a turtle's bone structure. Its vertebrae, pelvis, ribcage--it has no muscles between its ribs, which makes this...