Do Sharks Have Bones?

A shark does not have a single bone in its body – its skeleton is made
entirely of cartilage.

Sharks do not have bones. Instead, their skeletons are made of cartilage.
This connective tissue, like the kind found in human ears, is not nearly as
strong as bone and doesn’t fossilize over time like bones do. The
softness of cartilage has several advantages for sharks, such as making
them able to move more quickly through water, to live in tight spaces and
to heal more quickly from injuries. Sharks do have extra calcium deposits
similar to bone located in their skulls, jaws and spines as reinforcements
to add strength and stability. Some researchers believe that sharks might
be missing a gene that causes skeleton bone formation, but it is not
conclusively known why sharks have cartilage-based skeletons.
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