A big catch of fish fossils in southern China includes the oldest teeth ever found — and could help scientists learn how our aquatic ancestors got their bites.
The finds offer new clues to an important period of evolution that’s difficult to work out, because scientists haven’t found many fossils from that time so far. In a series of four studies, published Wednesday in the journal Nature, researchers describe some of their finds, from ancient teeth to never-before-seen species.
The fossils date from the Silurian Period, an important era for life on Earth from 443 million years ago to 419 million years ago. Scientists believe that our spineless ancestors, still swimming on a watery planet, may have started developing teeth and jaws around this time.
This allowed the fish to hunt for prey instead of “digging around” as bottom feeders, filtering food from the mud. It also led to a series of other changes in their anatomy, including different types of fins, said Philip Donoghue, a University of Bristol paleontologist and an author on 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 shift, said Matt Friedman, a University of Michigan paleontologist who was not involved in the study. They relied on fragments of the era—a bit of spine here, a bit of scale there.
The fossils from China are expected to fill some of those gaps as researchers around the world dig into them.
A field team discovered the fossils in 2019, Min Zhu, a paleontologist at the Chinese Academy of Sciences who led the study, said in an email. On a rainy day, after a frustrating journey that had yielded no fossils, researchers explored a pile of rocks near a cliff along the road. When they split open a rock, they found petrified fish heads staring at them.
After hauling more rocks back to the lab for research, the research team came up with a huge array of fossils that were in excellent condition for their age.
The most common species in the bunch is a small boomerang-shaped fish that likely used its jaws to scoop up worms, said Per Erik Ahlberg of Sweden’s Uppsala University, an author on one of the studies.
Another fossil shows a shark-like creature with bony armor on the front – an unusual combination. A well-preserved jawless fish offers clues as to how ancient fins evolved into arms and legs. While fossil heads for these fish are commonly found, this fossil encompassed the entire body, Donoghue said.
And then there are the teeth. The researchers found bones called gear teeth with multiple teeth on them. The fossils are 14 million years older than any other teeth of any kind found — providing the earliest solid evidence of jaws to date, Zhu said.
Alice Clement, an evolutionary biologist at Australia’s Flinders University who was not involved in the study, said the fossil find is “remarkable” and could rewrite our understanding of this period.
The wide range of fossils suggests there are many toothy creatures swimming around right now, Clement said in an email, even though it’s the next evolutionary era considered the “Age of Fishes.”
Dead fish breathe new life into the evolutionary origins of fins and limbs
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