“Though the shell is turtles’ signature design feature–and all sea turtles except the Leatherback live within rigid shells–Leatherbacks have, in a sense, no shell. Their ribs do not meet or fuse but remain an open lattice-work. Rather than a hard-bone carapace shingled with scaly scutes, the back forms over a jigsaw mosaic of thousands of small, thin–only a few millimeters–bones, overlaid by a thick matrix of oily fat and fibrous tissue. The belly consists only of a fragile, narrow oval of bone that’s filled in with an expanse of heavy, fibrous tissue several centimeters (more than an inch) thick. Rather than a domed back meeting a flat belly, the whole animal is rounder, more barrel-shaped. In different languages, the Leatherback’s names refer to its shape. In the Caribbean, for instance, it’s sometimes called Trunk or Trunk-back.”
–Carl Safina, Voyage of the Turtle: In Pursuit of the Earth’s Last Dinosaur
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