Four-hundred and forty million years ago, life on Earth’s land surface was scant. The bounty was beneath the waves. But an intrepid fungus, belonging to the genus Tortotubus, made that venture to land, and was key to laying the groundwork for all land-dwelling life following it.
University of Cambridge announced this week that microfossils from Sweden and Scotland represent not only the oldest fungal fossil, but also the oldest land-dweller fossil ever discovered.
The research was published in the Botanical Journal of the Linnean Society.
“During the period when this organism existed, life was almost entirely restricted to the oceans: nothing more complex than simple mossy and lichen-like plants had yet evolved on the land,” said the study’s author Martin Smith in a statement. “But before there could be flowering plants or trees, or the animals that depend on them, the processes of rot and soil formation needed to be established.”
First identified in the 1980s, the fossils, which are smaller than the width of a human hair, were once thought to be two separate organisms. However, Smith’s research pointed out that the specimens represented the same organism at different stages of growth.
Tortotubus’ cord-like structure is similar to extant fungi. Out of the main filament of modern fungi grow primary and secondary branches, which allow the organisms to spread and colonize the surfaces they grow on.
According to the University of Cambridge, life started transitioning from the oceanic to the terrestrial between 500 and 450 million years ago. A timeline of the evolution of life from New Scientist suggests plants began colonizing land around 465 million years ago. The oldest known living insects showed up around 400 million years ago, and the first four-legged animals appeared around 397 million years ago.
“Fungi play a vital role in the nitrogen cycle, in which nitrates in the soil are taken up by plant roots and passed along (the) food chain into animals,” according to the University of Cambridge. “Decomposing fungi convert nitrogen-containing compounds in plant and animal waste and remains back into nitrates, which are incorporated into the soil and can again be taken up by plants. These early fungi started the process by getting nitrogen and oxygen into the soil.”
Smith postulates that hundreds of millions of years ago Tortotubus would have been decomposing organisms, such as bacteria and algae. But since those organisms rarely leave fossils, it’s only a theory.
