Admit it. Your eyes glaze over when Aunt Marge drones on about her collection of salt and pepper shakers, or when geeky experts wax eloquent about their lifelong obsession, whether toy trains, stamps, quilts, airplanes, or racecars. I’m admittedly a geek about reptiles, with a deep fascination since childhood. In fact, for my PhD I studied Eastern box turtles for four years. But before you thumb past this article extoling the architecture of turtle shells—I promise you it’s more than an oddball obsession. Even folks who generally dislike reptiles don’t hold the same prejudice about turtles. They even stop to watch when a turtle crosses their path in the great outdoors. What is it about turtles that’s so intriguing? I’ll venture a guess. They capture our attention because turtles are either walking tanks or armored streamlined submersibles.
Unlike most reptiles, which escape danger by hiding or running, turtles carry around a protective shield and home all rolled into one. No other vertebrate does anything quite like this. A portable home requires special architectural designs — not just on the inside but for the whole body plan.
I prefer to think of turtles as walking cathedrals, temples that honor the Creator’s architectural skill, built long before Christopher Wren ever conceived of St. Paul’s Cathedral in London.
Light But Strong
The first challenge in building a walking cathedral is to be light and strong. What good is a sturdy roof if it’s too heavy to haul around? Turtle shells are made of special bones called osteoderms, which grow within and are a part of their skin (a marvel all by itself). To maximize strength and minimize weight, the shells are made out of a type of bone that has many open spaces in it (called spongy bone) sandwiched between two thin layers of dense, compact bone.