Turtles and tortoise represent a major breakthrough in self-defense: their scales have evolved into a hard shell over their backs, and bone supports their undershells, leaving their bodies encased in strong, unbreakable armor. When they come across danger, their head and legs pull back into their shells.
烏龜自誕生地球，對自身的保護就已有了極大的突破，它讓背部鱗片結成堅固的硬塊，底部也用骨頭支撐，身體封閉宛如穿上牢不可破的盔甲，遇到危險，就將四肢、頭縮進甲中。