Structure and fracture resistance of alligator gar (Atractosteus spatula) armored fish scales

The alligator gar is a large fish with flexible armor consisting of ganoid scales. These scales contain a thin layer of ganoine (microhardness ∼2.5 GPa) and a bony body (microhardness ∼400 MPa), with jagged edges that provide effective protection against predators. We describe here the structure of both ganoine and bony foundation and characterize the mechanical properties and fracture mechanisms. The bony foundation is characterized by two...