The upper shell of a turtle or tortoise is actually the ribcage. The individual ribs fuse together where they emerge from the spine and extend around the shoulders and pelvis of the animal to form a continuous carapace.
The underside of the shell is a separate piece made from the shoulder girdle and sternum (breastbone). So turtles don’t actually ‘live inside’ their shells, any more than you live inside your own rib cage.
But the shell isn’t made entirely of bone. It’s covered with around 54 plates of horn-like keratin that provide waterproofing and scuff-protection.
- What is the human body made of?
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Asked by: Vikram Rathaur, London
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Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.