Researchers at Oxford University studied the fossil of a fish skull from Siberia, which they believe provides evidence of the origins of all jawed vertebrates.
The 12-centimeter long skull was discovered in 1972 near the Sada River and initially classified as a bony fish. The researchers named the new genus Janusiscus schultzei after the Roman God Janus and its discoverer Hans-Peter Schultze.
The team used an advanced computer tomography scanner to analyze the skull. They also created a 3D model of it so they can look at it in different angles.
Initial analysis showed that the tiny fish skull is not really a bony fish, but rather a combination of bony fish and cartilage fish. Scientists have long-believed that jawed vertebrates are either made of bones or cartilage, but not both.
The scans showed that the fossil has sensory line canals that bony fish use to detect pressure changes, and blood vessels that supply oxygen to the brain that is common on cartilage fish.
"It's a very interesting fossil, and it's very small," said Sam Giles, study lead researcher and a paleobiology doctoral candidate at Oxford University in the United Kingdom, to LiveScience. "It's surprising that something so tiny could have so much information in it."
The findings of the study hint that the shark's evolution is only recent. Scientists previously thought it is primitive.
"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," said Dr Matt Friedman of Oxford University's Department of Sciences in a press release.
The tiny fish skull offers more understanding on evolutionary transition, from primitive jaw fish to modern jaw fish. But further study is needed to determine how the two types of jawed vertebrates evolved separately.
The study was published in the Jan. 12 issue of the journal Nature.
