The hard external supporting and protecting structure in many invertebrates, such as mollusks and crustaceans, and certain vertebrates, such as turtles; exoskeleton.

• 骨干：许多非脊椎动物身体外部起支持和保护作用的结构，例如软体动物和甲壳纲的动物，另外还包括一些脊椎动物，例如海龟；外骨骼