black brown browns colors colours contours cover dips exterior grooves hard horny plates layers lines outlines pointed points protection rough shapes shell shelter sides solid strength strong textures tips tortoise tortoise shell tough white abstract aged aldabra-giant-tortoise aldabrachelys-gigantea appearance armor armored armorment armour armoured armourment carapace giant-tortoise hide horny-plates leathery lined longevity old protective reptile reptilian size skin texture textured zoo