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.
More about sharks:
- The species of shark known as the whale shark has been found to live for as long as 100 years.
- Shark fossils, such as teeth, have been discovered that are thought to date back 400 million years, possibly making them older than dinosaurs.
- Sharks can go six weeks without eating because they can live off their thick layers of blubber for energy.
