Imagine if we knew what the oldest known organism on planet Earth was. Now, scientists think that they may have found it. They've discovered a fossil dating from 440 million years ago that's the oldest known example of a fossilized fungus and could have helped colonize Earth.
The early fungus is known as Tortotubus and displays a structure similar to one found in some modern fungi. This likely allowed it to store and transport nutrients through the process of decomposition. While it can't be linked to be the first organism on land, it is the oldest yet found.
"During the period when this organism existed, life was almost entirely restricted to the oceans: nothing more complex than simply mossy and lichen-like plants had yet evolved on the land," said Martin Smith, who conducted the work while at the University of Cambridge's Department of Earth Sciences. "But before there could be flowering plants or trees, or the animals that depend on them, the process of rot and soil formation needed to be established."
In this latest study, the researchers worked with a range of tiny microfossils to reconstruct the method of growth for two different types of fossils that were first identified in the 1980s. These fossils had once been thought to represent parts of two different organisms, but by identifying other fossil with "in-between" forms, the scientists showed that the fossils actually represented parts of a single organism at different stages of growth.
Fungi play a vital role in the nitrogen cycle, in which nitrates in the soil are taken up by plant roots and passed along food chain into animals. 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. In other words, they were the first colonizers of Earth and paved the way for other organisms.
In this case, the researchers found that Tortotubus had a cord-like structure, similar to that of some modern fungi, in which the main filament sends out primary and secondary branches that stick back into the main filament, eventually enveloping it. This cord-like structure is often seen in land-based organisms, allowing them to spread out and colonize surfaces. In modern fungi, the structure is associated with the decomposition of matter, allowing a fungus colony to move nutrients to where they are needed-a useful adaptation in an environment where nutrients are scarce and unevenly distributed.
The new findings reveal a bit more about early terrestrial organisms. This helps scientists learn a bit more about evolution and what creatures may have existed millions of years ago in addition to which creatures may have helped colonize early Earth.
