Fracture Mitigation Strategies in Gastropod Shells

For hundreds of millions of years, gastropods have been evolving, modifying their external calcified shells for defense against shell-breaking and drilling predators. They have evolved primarily to use two different aragonitic microstructures: the evolutionary older Nacre (mother of pearl) structure and the more recently developed crossed-lamellar structure. By using both of these structures, gastropods are able to produce shells that are significantly tougher then geologic aragonite. However, the crossed-lamellar structure allows for a wider variety of shell morphologies, ensuring its increasing presence since the Mesozoic Marine Revolution more than 200 million years ago.