Paleontologists discover fossil fungi a billion years old in Canada | Paleontology

An international team of paleontologists has discovered microfossils of a 1000- to 900-million-year-old fungus in estuarine shales of the Grassy Bay Formation in the Canadian Arctic. These microfossils with multicellular organic walls are more than half a billion years older than previously reported fungi occurrences.

"Mushrooms are essential components of modern ecosystems and are among the first traces of life to colonize continents," said Corentin Loron, a researcher at the University of Liège, and his colleagues.

"To date, the first fungal fungi are 410 million-year-old specimens of Scotland and 450-million-year-old Wisconsin glomeromycotus mushroom spores in the Ordovician era."

"The fossil fungi of the Grassy Bay Formation dating from 1-0.9 billion years ago (Proterozoic Period) are older than those previously reported fossils of more than half a billion dollars. years. "

Paleontologists have discovered an abundance of microfossils from a fungus named Ourasphaira giraldae.

These fossilized specimens have a wall consisting of chitin, a fibrous compound that forms fungal cell walls.

"These microfossils with organic walls consist of multicellular branched filaments with terminal spheres," the scientists said.

"Scanning electron microscopy and transmitted light (SEM) examinations show smooth, unadorned walls of filaments and spheres."

"SEM images also reveal the presence of locally well-preserved and interlaced microfibrils (about 15 to 20 nm thick) that make up the walls."

"Ultrastructural analyzes using transmission electron microscopy show that flattened microfossils are hollow, with a bilayer wall composed of a thick inner layer of electrons and a thin outer layer of electrons."

This combination of complex morphology, right-angle branching, multicellularity, ultrastructure of the bilayer wall, composition recalibration and relatively large size allows the unambiguous placement of Ourasphaira giraldae among eukaryotes. "

"Together, they indicate the presence of a complex cytoskeleton, absent in prokaryotes."

Existing fungi are mainly terrestrial, although some marine forms are known.

Because Ourasphaira giraldae is preserved in shallow-water estuarine schists of the Grassy Bay Formation, this fungus may have lived in an estuarine environment. The fungus may also have been transported in this estuarine environment from terrestrial or marine niches.

"The later colonization of terrestrial environments by fungi may have preceded and favored the colonization of land by plants through symbiosis and soil treatment, which would have provided ecological niches, improved substrate, uptake of nutrients and increased aerial productivity, "the researchers said.

"As multi-disciplinary studies on Proterozoic fossil assemblages progress, we anticipate that more fossil fungi and other early eukaryotes will be discovered and will improve our understanding of the evolution of the early biosphere."

The discovery is reported in an article published this week in the newspaper Nature.

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Corentin C. Loron et al. First Proterozoic mushrooms of the Canadian Arctic. Nature, published online May 22, 2019; doi: 10.1038 / s41586-019-1217-0