Earliest fungi

The earliest fungi known are currently unnamed microfossils discovered in dolomite shale from the Democratic Republic of the Congo estimated to be 715–810 million years old. They consist of carbonaceous filaments of less than 5 micrometres (μm) in width, which exhibit low-frequency septation (pseudosepta) and high-angle branching that can form dense interconnected mycelium-like structures. They have also been shown to contain vestigial chitin (a compound found in fungal cell walls), which together with the above characteristics confirm them to be remnants of fungal networks. This discovery was formally published in the journal Science Advances on 22 January 2020.

In May 2019, a paper was published in Nature concerning the discovery of what were claimed to be fossilized microfungi dating back 1 billion years in the Canadian Arctic. Again, it was claimed that chitin was present within these fossils, suggested by chemical analysis. However, Sylvain Bernard, a geochemist at the Institute of Mineralogy, Physics of Materials and Cosmochemistry in Paris, France, pointed out that the presence of many organic molecules could produce similar results, and the findings from the chemical analysis also suggested the presence of molecules not typically found in chitin. In his view (as well as that of other prominent scientists), therefore, the data does not conclusively show that these microfossils originally contained chitin, so at present their status as fungi remains contentious.