A sea turtle’s shell is living bone fused directly to its spine and ribs. It is not a detachable shield or an external case, as certain quirky cartoons have shown. The shell grows with the turtle, ...

Sometimes animated turtles seem to live inside their shells like it’s a tiny home. They may even hop out of the shell and run around. That’s funny in cartoons and games, but my friend Ryan Wagner told ...

Sea mollusc shells are patterned not through conscious control, but by chemistry acting at the shell’s growing edge. A thin strip of tissue known as the mantle secretes both the shell material and its ...