  A fibrous herringbone-modified helicoidal architecture is identified within
the exocuticle of an impact-resistant crustacean appendage. This previously
unreported composite microstructure, which features highly textured apatite
mineral templated by an alpha-chitin matrix, provides enhanced stress
redistribution and energy absorption over the traditional helicoidal design
under compressive loading. Nanoscale toughening mechanisms are also identified
using high load nanoindentation and in-situ TEM picoindentation.
