age aged armor armored armorment armour armoured armourment carapace elongated-neck giant-tortoise herbivore hide large-tortoise leathery longevity neck old plod plodding protection protective reptile reptilian shell size skin slow strength strong texture textured textures tortoise zoo abstract appearance astrochelys-radiata critically-endangered endangered giant tortoise large tortoise Madagascar radiated-tortoise aldabra giant tortoise aldabrachelys gigantea eating eating grass elongated neck Seychelles rough scaly tough