Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hypermineralized hammer-like dactyl clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one species, Odontodactylus scyllarus, exhibit an impressive set of characteristics adapted for surviving high-velocity impacts on the heavily mineralized prey on which they feed. Consisting of a multiphase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines of defense against catastrophic failure during repetitive high-energy loading events.

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During mineralization, the hard outer magnetite‐containing shell of the radular teeth of Cryptochiton stelleri undergoes four distinct stages of structural and phase transformations: (i) the formation of a crystalline α‐chitin organic matrix that forms the structural framework of the non‐mineralized teeth, (ii) the templated synthesis of ferrihydrite crystal aggregates along these organic fibers, (iii) subsequent solid state phase transformation from ferrihydrite to magnetite, and (iv) progressive magnetite crystal growth to form continuous parallel rods within the mature teeth. The underlying α‐chitin organic matrix appears to influence magnetite crystal aggregate density and the diameter and curvature of the resulting rods, both of which likely play critical roles in determining the local mechanical properties of the mature radular teeth.

Ecological pressures and varied feeding behaviors in a multitude of organisms have necessitated the drive for adaptation. One such change is seen in the feeding appendages of stomatopods, a group of highly predatory marine crustaceans. Stomatopods include "spearers," who ambush and snare soft bodied prey, and "smashers," who bludgeon hard-shelled prey with a heavily mineralized club. The regional substructural complexity of the stomatopod dactyl club from the smashing predator Odontodactylus scyllarus represents a model system in the study of impact tolerant biominerals. The club consists of a highly mineralized impact region, a characteristic Bouligand architecture (common to arthropods), and a unique section of the club, the striated region, composed of highly aligned sheets of mineralized fibers. Detailed ultrastructural investigations of the striated region within O. scyllarus and a related species of spearing stomatopod, Lysiosquillina maculate show consistent organization of mineral and organic, but distinct differences in macro-scale architecture. Evidence is provided for the function and substructural exaptation of the striated region, which facilitated redeployment of a raptorial feeding appendage as a biological hammer. Moreover, given the need to accelerate underwater and "grab" or "smash" their prey, the spearer and smasher appendages are specifically designed with a significantly reduced drag force.

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