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The oldest evidence of earth mushroom may be a small 635 million year old microfossil found in a cave in southern China.
Too small to be seen with the naked eye, this remarkable discovery delays the appearance of the terrestrial fungus from about 240 million years ago to a period known as “snowball earth“When the planet was locked in ice 750 million to 580 million years ago.
The presence of terrestrial fungi at this critical point may have helped Earth transition from a frozen scoop of ice to a planet with a variety of ecosystems that can harbor various life forms, scientists wrote in a new study. By breaking down minerals and organic matter and recycling nutrients back to the atmosphere and ocean, ancient fungi could have played an important role in reshaping the Earth’s geochemistry, creating more hospitable conditions that opened up the pathway for the emergence and growth of land plants and animals.
Related: Images: The oldest fossils in the world
Scientists have discovered the fossilized filamentary filaments – a hallmark of fungal structures – in sedimentary rocks of the Chinese Doushantuo Formation in Guizhou Province, dating from the Ediacaran period (there are about 635 million to 541 million years). Identifying rocks that might contain microscopic fossils takes both luck and skill, said study co-author Shuhai Xiao, professor of geosciences at the Virginia Tech College of Science (VT) in Blacksburgh, Virginia.
“There is an element of serendipity, but there is also an element of experience and expectation. Having worked with microfossils, you know what kind of rocks to look at,” Xiao told Live Science. For example, rocks must be fine grained, because fossils are so small. Color can also provide clues; biological carbon in microfossils can make fossil rocks darker than rocks that do not contain fossils.
“But it’s not error-proof; most of the time we cut a stone and can’t find anything. There is maybe a 10% success rate,” Xiao said.
Sliced
To find the fossils, the study’s authors crushed slices of rock thin enough for light to penetrate, measuring no more than 50 microns thick. Powerful microscopes revealed the tiny tendrils of the fungus, which were only a few microns in diameter – about 1/10 the width of a human hair. Under the microscopes, traces of organic carbon in the fossils were darker than the rock around them.
The researchers also used more advanced microscopy to examine the fossils and build digital copies of their structures. Fortunately, many of these structures “have been perfectly preserved in three dimensions,” said lead author of the study Tian Gan, a doctoral student at the Chinese Academy of Sciences in Beijing and visiting scholar at VT, in an email. .
These branched filaments told researchers that the fossils were of biological rather than mineral origin. Although certain types of bacteria also produce branches, the closest analogues of these types of filaments are fungal, and the small spheres in the fossil “could be interpreted as fungal spores”, supporting the hypothesis that these microorganisms were a type of fungus, the scientists wrote. .
Old life
Fossil evidence of the first organisms on Earth is exceptionally scarce, but this microfossil and other recent discoveries are helping researchers slowly piece together important clues about when life first appeared.
The oldest evidence of marine fungus, described in 2019 from rocks found in Canada, dates back about a billion years; the oldest forest, described in 2020 from fossilized roots in upstate New York, is 386 million years old; and the oldest known animal – a bizarre oval-shaped creature called Dickinsonia – is around 558 million years old (fossils that were once considered to represent older animals have recently been attributed to ancient algae, Live Science reported in December 2020).
Fossilized structures of Canada which may have been built by microbes between 3.77 billion and 4.29 billion years ago represent one of the oldest examples of life on Earth. Other structures preserved in the rock of Greenland are also believed to have microbial origins and are 3.7 billion years old. Another fossil from Western Australia may contain microbes that are 3.5 billion years old, although some scientists have argued that geothermal activity may have modified chemicals in the rock to make them look like with biological traces Previously reported Live Science.
Scientists first linked terrestrial fungi to the appearance of terrestrial plants, from fossils from the Rhynia cherts in Scotland which preserve plants and fungi together and date to around 410 million years ago, Xiao said. In these fossils, “plants and fungi have already established a kind of ecological relationship,” he explained.
However, the mushroom fossils that predated the earliest known plants have suggested that terrestrial fungi first appeared, around 450 million years ago, “and now we are extending that to 635 million years,” he said. Xiao said.
The results were published online Jan. 28 in the journal Nature communications.
Originally posted on Live Science.
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