“Diamond” starfish

It has been recently discovered that some species of modern starfish form a calcite skeleton with a triply periodic trabecular microstructure resembling the atomic structure of diamond, composed of a network of hexagonally ordered four-armed tetrapods, which gives them extraordinary mechanical strength, optimum packing in space, and minimum material expenditure. We described a similar microstructure in a Devonian crinoid from the Holy Cross Mountains. Such a highly ordered microstructure, additionally enriched in magnesium, might have developed in these echinoderms in response to increased predation pressure.