Use 'cartilaginous' when talking about animals with parts made of cartilage instead of bone. Stingrays are fascinating due to their cartilaginous bodies.
Pro Tip 2/3
Not Just Fish
'Cartilaginous' isn't exclusive to describing fish, it's used for any cartilage-based structure. Some cartilaginous structures in humans include the ear and nose.
Pro Tip 3/3
Flexibility
Emphasize the flexible nature of cartilage compared to bone when using 'cartilaginous.' The cartilaginous nature of the nose allows it to endure bending without breaking.