Scientists have found the world’s oldest terrestrial fossil hiding inside 635-million-year-old sedimentary dolostone rocks from China.
Researchers estimate the record-setting fungi played a key role in ending the “snowball Earth” ice age that frozen Earth solid 650 million years ago.
The finding was described Thursday in a new paper, published in the journal Nature Communications.
“It was an accidental discovery,” lead study author Tian Gan said in a news release.
“At that moment, we realized that this could be the fossil that scientists have been looking for a long time. If our interpretation is correct, it will be helpful for understanding the paleoclimate change and early life evolution,” said Gan, a postdoctoral researcher with the Chinese Academy of Sciences.
Gan is currently working as a visiting researcher in the laboratory of study co-author Shuhai Xiao, a professor of geosciences at Virginia Tech.
Since scientists first found evidence of the planet’s snowball-Earth episode, they’ve struggled to explain how life survived and ultimately returned to normal.
Upon discovering the fungi microfossil, Gan and Xiao became convinced that the tiny, cave-dwelling organism helped reverse the feedback loops that plunged the planet into a deep ice age.
Fungi help plants colonize terrestrial environments by breaking down rocks and tough organic matter, recycling nutrients that can both be utilized by plants on land and carried to the ocean where they can feed marine microorganisms.
“Fungi have a mutualistic relationship with the roots of plants, which helps them mobilize minerals, such as phosphorus,” Gan said.
“Because of their connection to terrestrial plants and important nutritional cycles, terrestrial fungi have a driving influence on biochemical weathering, the global biogeochemical cycle, and ecological interactions,” Gan said.
Studies have previously traced the origins of the alliance between plants and fungi back some 400 million years on the evolutionary timeline, but some scientists have wondered whether fungi might have emerged prior to terrestrial plants.
“I think our study suggests yes,” Xiao said. “Our fungus-like fossil is 240 million years older than the previous record. This is, thus far, the oldest record of terrestrial fungi.”
For decades, the upper dolostone layers of South China’s Doushantuo Formation have yielded a plethora of fossils, but scientists never expected to find fossils among the formation’s bottom layers.
It wasn’t long ago that researchers doubted whether the remains of tiny organisms like fungi could be preserved in ancient rocks.
Now, scientists have evidence that fungi and other microorganisms persisted in ancient caves during snowball Earth, plotting a return to normalcy.
Moving forward, researchers plan to explore the relationships between the newly discovery fungi and other organisms living in the ancient cave.
“It is always important to understand the organisms in the environmental context,” said Xiao. “We have a general idea that they lived in small cavities in dolostone rocks. But little is known about how exactly they lived and how they were preserved. Why can something like fungi, which have no bones or shells, be preserved in the fossil record?”
By : Brooks Hays – UPI