A team of University of Cambridge scientists has discovered the earliest example of a land-dwelling organism - an early fungus - thanks to a fossil dating from 440 million years ago. The organism is believed to have stimulated the processes of soil and root formation, which are vital to all land life, and laid the groundwork for more complex plants and animals.
The fungus, known as Tortotubus, possesses a structure similar to some modern fungi, allowing for the storage and transportation of nutrients through decomposition. While scientists cannot yet say that it is the first organism to have lived on land, it is the oldest fossil known thus far.
"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," Martin Smith, author of the paper, said in a press release. "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."
Smith worked with numerous tiny microfossils gathered from Sweden and Scotland and attempted to reconstruct the method of growth for two that were discovered in the 1980s. He was able to show that each fossil was actually a part of a single organism at different growth stages and identified the fossils as mycelieum, the root-like filaments that fungi use in order to gather nutrients from the soil.
Subsequently, Smith discovered that Tortotubus had a cord-like structure that resembles modern fungi, using a main filament to send out primary and secondary branches that are attached back onto main filament, eventually consuming it. These structures, often seen in land-based organisms, allow them to spread out and make their home on surfaces.
"What we see in this fossil is complex fungal 'behaviour' in some of the earliest terrestrial ecosystems - contributing to soil formation and kick-starting the process of rotting on land," Smith said.
"This fossil provides a hint that mushroom-forming fungi may have colonized the land before the first animals left the oceans," he concluded. "It fills an important gap in the evolution of life on land."
The findings were published in the March issue of the Botanical Journal of the Linnean Society.
