Fossil upends theory of how shark skeletons evolved, say scientists – The Guardian

The partial skull of an armoured fish that swam in the oceans over 400m years ago could turn the evolutionary history of sharks on its head, researchers have said.
Bony fish, such as salmon and tuna, as well as almost all terrestrial vertebrates, from birds to humans, have skeletons that end up made of bone. However, the skeletons of sharks are made from a softer material called cartilage even in adults.
Researchers have long explained the difference by suggesting the last common ancestor of a…

Click here to view the original article.