Cover image: Computed tomography (CT) scans reveal the mineralized portions of the skeletons of an array of batoid fish species (stingrays and relatives). Although the skeletons of rays and sharks are primarily radio-lucent uncalcified cartilage, they are crusted with a layer of mineralized tiles that shows up in x-rays. Like most of the composite biological materials highlighted in this issue's symposium, "Biomaterials: Properties, Variation and Evolution," the combination of tissues imparts emergent mechanical advantages—in this case, high stiffness and high mechanical damping—sidestepping the limitations of any one of the constituents. Submitted by Mason Dean.
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