Tough, flexible tissue that can support the body instead of bone. For example, humans have cartilage in our nose and ears. A 'cartilaginous' animal such as a stingray or shark has cartilage inside instead of bone.

There are two meanings of the word spine: 1. The backbone of a creature that extends from the bottom of their head/skull all the way down their back. And 2. a stiff, pointed, part that sticks out from a creature. E.g. the pointy spines of a fish or kina.