When I first heard that the Earth was once covered by giant fungi, the image that appeared in my mind was of enormous mushrooms with colossal caps. However, the type of fungus that dominated the world at that time was “Prototaxites”, which is quite different from the fungi we know today.
A Mystery Over a Century Old
According to The University of Chicago magazine, the genus Protomycota is believed to have existed between 430 million and 350 million years ago. C. Kevin Boyce, a geophysicist at the university, stated, “At that time, this land was inhabited only by insects and small plants. Therefore, protomycetes were probably the largest land-dwelling organisms on Earth at that time.”
The fossils of the genus Protomycota were not discovered until the mid-19th century. Since then, its fossils have been found in Saudi Arabia, Australia, Canada, and other locations. Research indicates that they could even reach a maximum height of 8 meters and a trunk diameter of about 1 meter.
Prototaxites is a genus of land-dwelling fossil fungi dating from the late Silurian to the late Devonian periods. Prototaxites formed large structures resembling tree trunks, up to 1 meter wide and 8 meters long, made from interwoven tubes approximately 50 micrometers in diameter, making it the largest terrestrial organism of its time. (Image: ZME).
In fact, over the past 150 years, scientists have debated exactly what the Protomycota genus is. Initially classified as conifers, they were later thought to be lichens or algae. Ultimately, most began to realize that they were indeed fungi.
Boyce stated that the main issue with protomycetes is that “when you look closely at their anatomy, it evokes many different things. Their size also makes it hard to imagine.”
It wasn’t until 2007 that Boyce discovered how to use geochemistry to study these mysterious organisms. Although they are fossils, their carbon isotopes can also be analyzed.
Like a Giant Root System
In a scholarly article published in Canadian Journal of Microbiology in 2022, a group of scientists compared samples of protomycete fungi from quarries in Germany and Canada with contemporary fungi. Each type was studied using various modern and powerful microscopes.
They found that the structures in the fossils closely resembled modern root-like bodies found in certain fungi that they grew in the laboratory.
These root-like appendages allowed the fungi to transport nutrients over long distances. Additionally, these fungi also consumed other organisms.
The researchers explained that protomycetes, both fossilized and modern fungi, “comprise tubular structures of similar length and diameter, merging to form tissue-like material.” Furthermore, in their laboratory, they observed microscopic images of root-like bodies in which fungi develop.
From a distance, the fossils appear trunk-like, slightly widening near the base, suggesting a connection to root-like structures. Prototaxites were perhaps the tallest living organisms during their time. At the microscopic level, the fossils consist of narrow tubular structures intertwined with each other. They come in two types: “skeletal” tubes, 20–50 μm in diameter, with thick walls (2–6 μm) that are not divided along their lengths, and capable of reproduction. (Image: Zhihu).
However, they have a major point of disagreement: the research team does not believe that protomycetes grew vertically . From their perspective, fungi developed horizontally. And there is indeed some logic supporting their viewpoint.
First, no specimens have been recorded standing upright on the ground. Clearly, in the fossils, they are all lying down. Moreover, nutrient gathering would be more efficient if these fungi lay horizontally, especially in a real-world environment. The researchers noted:
“At that time, the abundance of live plants and the accumulation of dead plant matter were available for fungi to decompose.” Clearly, a horizontal orientation would allow protomycetes to spread further in search of nutrients and water.
Although most people support the idea that protomycetes were upright, tree-like organisms due to their trunk structure, this association gives us a different picture of the world long ago.
First collected in 1843, it wasn’t until 14 years later that John William Dawson, a Canadian scientist, studied the Prototaxites fossil, which he described as giant conifer-like plants partially decayed. (Image: ZME).
While for us, ten thousand years may seem like a long time, this period is merely a blip in the history of the Earth.
We do not know what the Earth looked like hundreds of millions of years ago. And our understanding of this world still appears to be quite superficial.
