A new study of a fossilized fish skull dismissed the popular theory modern bony fish evolved from sharks. It also showed humans evolved from what are called "cartilaginous fishes".

Researchers from the Imperial College London and Oxford University examined a 415 million year-old fossil and found out that sharks aren't as primitive as their ancestors.

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Using CT scans and X-rays, researchers studied the fossil they called "Janusiscus" for its two-faced feature. The fossil was named after the two-faced Roman god, Janus.

Janusiscus's brain case is an internal skeleton made of cartilage. This makes the fossil more similar to the cartilaginous fish family that includes sharks and rays than the bony fish family.

In addition, the absence of a division on the bottom of the skull indicates that its evolution is in the infancy stage. Present-day sharks similarly lack external skulls.

The scans showed the fossil also has an external skull, albeit smaller. Researchers suggested that sharks lost the skeleton on their faces early in their evolution.

The two features Janusiscus possesses branched out to two families in the evolution history: cartilaginous fish and bony fish. The former further evolved to land vertebrates and finally, humans.

"This mix of features, some reminiscent of bony fishes and others cartilaginous fishes, suggests that humans may have just as many features that you might call 'primitive' as sharks," Oxford University's Department of Earth Sciences researcher Matt Friedman said.

Experts previously pinned sharks on the primitive stage of the evolution history because of its external features but recent findings led them to give sharks another look.

"Janusiscus has helped us to look at sharks differently," said Martin Brazeau of Imperial College of London's Department of Life Sciences.

The fossil provided researchers new evolutionary insights, Dr. Brazeau added.

Janusiscus was discovered in 1972 in Siberia and is currently kept at the Tallinn University of Technology in Estonia.

Tagssharks, evolution, Janusiscus, Imperial College London, Oxford University, Fossil, Research, Study