While humans have a bony skeleton, parts of our bodies – such as our noses – are made of cartilage. This soft, flexible material forms the entire skeletons of sharks and rays.
We have long known that the ancient ancestors of both bony and cartilaginous animals had skeletons made of cartilage. This means that cartilage was the ‘ancestral state’ that we all once had.
Scientists once thought that the ancestors of sharks and rays never evolved bone, but one fossil changed that idea. Minjinia turgenensis was an ancient jawed fish. It was thought to be an ancestor of both bony and cartilaginous creatures, yet it was bony. This means that sharks and rays probably re-evolved a cartilaginous skeleton from a bony one.
A cartilaginous skeleton is likely to be useful for oceanic predators because it is lightweight. While more constraining than a bony skeleton in terms of the shapes it can support, it allows for quicker swimming, tighter turning circles and better buoyancy. For sharks and rays, at least, cartilage is clearly an excellent adaptation.
Discover more amazing wildlife stories
- Ancient animal filmed slithering over the seafloor near Komodo island
- Gigantic iceberg breaks free in Antarctica, revealing ghostly mega-nest beneath
- Formidable crocodile-like predator discovered in Egyptian desert
- Diver drops into Caribbean Sea at night, then tentacled animal rises from depths with unusual things inside it
Top image: tiger shark. Credit: Getty
