Oldest teeth ever found in fossil fish catch in China

NEW YORK (AP) — A big catch of fish fossils in southern China includes the oldest teeth ever found — and may help scientists understand how our aquatic ancestors were bitten.

The findings offer new clues to a key period in evolution that has been difficult to flesh out because until now scientists have not found many fossils from that time. In a series of four studies, published Wednesday in the journal Nature, the researchers detail some of their findings, from ancient teeth to never-before-seen species.

The fossils date back to the Silurian period, a significant era for life on earth from 443 million years ago to 419 million years ago. Scientists believe that our spiny ancestors, who were still swimming on an aquatic planet, may have started developing teeth and jaws around this time.

This allowed the fish to hunt for prey instead of “foraging” as bottom feeders, filtering food from the mud. It also triggered a range of other changes in their anatomy, including different types of fins, said Philip Donoghue, a paleontologist at the University of Bristol and author of one of the studies.

“It’s just at this interface between the Old World and the New World,” Donoghue said.

But in the past, scientists haven’t found many fossils to show this change, said Matt Friedman, a University of Michigan paleontologist who was not involved in the research. They relied on fragments from the era – a piece of spine here, a bit of scale there.

Fossils from China should fill in some of these gaps as researchers around the world study them.

A field team discovered the fossil treasure in 2019, Min Zhu, a paleontologist at the Chinese Academy of Sciences who led the search, said in an email. One rainy day, after a frustrating journey that turned up no fossils, researchers explored a pile of rocks near a roadside cliff. When they split a rock, they found fossilized fish heads staring at them.

After bringing more rocks back to the lab for examination, the research team ended up with a vast array of fossils that were in very good condition for their age.

The most common species in the group is a small, boomerang-shaped fish that likely used its jaws to pick up worms, said Per Erik Ahlberg of Sweden’s Uppsala University, author of one of the studies.

Another fossil shows a shark-like creature with bony armor on its front – an unusual combination. A well-preserved jawless fish offers clues as to how ancient fins evolved into arms and legs. While fossil heads of these fish are commonly found, this fossil included the entire body, Donoghue said.

And then there are the teeth. The researchers found bones called dental whorls on which several teeth grow. The fossils are 14 million years older than any other teeth found in any species – and provide the first solid evidence of jawbones to date, Zhu said.

Alice Clement, an evolutionary biologist at Flinders University in Australia who was not involved in the research, said the fossil find is “remarkable” and could rewrite our understanding of this time period.

The wide range of fossils suggests there were plenty of toothy swimming creatures around this time, Clement said in an email, even though it’s the next evolutionary era that’s considered “the era of Pisces”.

The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Department of Science Education. The AP is solely responsible for all content.

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