The Stomatopod Dactyl Club: A Formidable Damage-Tolerant

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. The stomatopods are an ancient group ofmarine tropical and subtropical crusta-ceans with a fossil record that dates back more than 300 million years (1). Modern repre-sentatives reach lengths of nearly 40 cm, al-though most species are appreciably smaller (e.g., 15 cm). To the casual observer, they super-ficially resemble heavily armored caterpillars