Researchers think a 440 million-year-old fungus, recently found in fossilized form, jump-started the process of rot and soil formation on Earth, paving the way for more diverse land-based life forms.

The fossil fungus, unearthed in Sweden, is the oldest ever found and the oldest example of a land-dwelling organism.

Though it wasn't the first organism to begin life on land, the fungus, Tortotubus, likely played an important role in making the solid ground more suitable for other organisms. Its ability to store and transport nutrients through decomposition helped create a nutrient-rich layer of topsoil.

Researchers detailed their discovery in the Botanical Journal of the Linnean Society.

Tortotubus featured a series of cord-like filaments that hung from a main tube. The filaments stretched into the soil, leeching nutrients from decaying plant and animal matter and waste. Similar designs are found among some modern fungi.

Tortotubus' presence not only helped created richer, deeper soil, it also helped incorporate oxygen and nitrogen into the dirt.

"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," study author Martin Smith, an earth scientist who led the researcher while at the University of Cambridge, said in a news 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."

Researchers believe the earliest organisms to populate the land showed up between 500 million and 450 million years ago, during the Palaeozoic era. The latest discovery suggests mushrooms may have been one of the first.

"This fossil provides a hint that mushroom-forming fungi may have colonized the land before the first animals left the oceans," said Smith. "It fills an important gap in the evolution of life on land."