Ancient tiny fish fossil sheds light on evolution of jawed vertebrates

By Brooks Hays   |   Jan. 13, 2015 at 11:56 AM
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OXFORD, England, Jan. 13 (UPI) -- The advent of the jaw among vertebrates was quite a moment -- essential, really. The jaw, the hinge-operated vault of the mouth, opened up a wide world of possibilities for creatures looking to satisfy those ceaseless hunger pangs.

The jaw proved so popular among animals, it can be seen today throughout the Animal Kingdom, from tigers to crocodiles, from sharks to humans.

Now, researchers at Oxford University in England suggest a tiny, ancient fish fossil discovered in Siberia could explain the jaw's evolutionary origin. The 415-million-year-old fish skull was unearthed in the 1970s, but researchers are only just now coming to realize its paleontological importance.

The fish (Janusiscus schultzei) is named for the Roman god Janus and for Hans-Peter Schultze, the University of Kansas researcher who first described the specimen in 1977. Schultze and his colleagues determined that the ancient skull belonged to a bony fish. In the beginning, fish were the first vertebrates to sport jaws, and there were two kinds, those with bones and those with cartilage.

But scientists have yet to ascertain exactly when and where to the two kinds diverged on the evolutionary timeline.

"There are over 60,000 species of living jawed vertebrates, and they encompass pretty much everything you can think of [with a backbone] that lives on land or in the sea," lead researcher Sam Giles, a paleobiology doctoral candidate at Oxford, told Live Science. "But we don't really know what they looked like when they split."

Analysis by Giles and his colleagues, however, revealed that the ancient skull exhibits characteristics of both bony fish and those with cartilage -- suggesting Janusiscus schultzei was one of the two groups' shared ancestors.

"I think it is a highly significant discovery, as the origin and diversification of modern bony-jawed fishes is still shrouded in mystery," said John Long, an paleontologist who wasnt' involved in the study. "But Janiusiscus takes us a big step closer to really understanding this major evolutionary transition, from primitive jawed fishes to the beginning of the modern jawed fish fauna."

The new research was published this week in the journal Nature.

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