385 million-year-old shark fossil reveals sharks and humans had a common ancestor

A 385 million-year-old shark fossil has revealed that there once lived a prehistoric creature that was a common ancestor to both sharks as well as humans. The prehistoric shark lived during the Devonian period, which lasted from about 420 million to 360 million year ago. This was when four-legged animals first began dominating the evolutionary process.

The prehistoric shark, which was discovered in 2001, belongs to a species called Gladbachus adentatus. The species was named after the German city Bergisch Gladbach, where the shark was found. Although the shark was previously thought to have a toothless jaw, recent analysis of the fossil found that it had teeth.

Michael Coates, a professor in the Department of Organismal Biology and Anatomy at the University of Chicago, who is the lead researcher of the new study, told LiveScience that unlike other shark fossils discovered, which are "usually preserved as a mess of tiny scales and teeth and not much else," this Devonian shark's bones were still in place.

"The body is preserved as a sheet of prickly scales," Coates said. "The skeleton of the head has a very course grain to it, almost like the pattern of tree bark."

Scientists performed scans on the prehistoric shark, the only one ever to be found from the Devonian period, to find that sharks and the human ancestor split around 440 million years ago during the Silurian period.

The fossil also revealed more information about the evolutionary history of sharks. "As such, [it] reveals new information about the diversity of early sharks that we haven't had access to before," Coates reportedly said.

However, the new information has also complicated researchers' understanding of sharks' lineage. The study suggests that shark evolution has more branches than previously known, several of which converged. This in turn led to the development of the signature features of modern sharks such as multiple gills and long throats.

The findings of the new study have been published in the journal Proceedings of the Royal Society B.