Comparitive Anatomy: How the Turtle Got Its Shell

You might need a short anatomy review before reading this one. The turtle's shell is basically made from a fusion of its ribs to the vertebrae. The trick is that the shoulder blade (scapula) grows deeper than the rib cage, rather than on top of it (like ours).

This adjustment of the shoulder blade causes a "muscular origami" when the torso musculature is forced to develop differently.

In the end, it is not possible for a turtle to come out of his shell, as the cartoons suggest.