Back when the tallest trees were only a few feet high, huge towers of fungus grew in excess of 8 meters.
The terrestrial landscape was very different 400 million years ago - so much so in fact that, rather than plants and trees, this prehistoric era was dominated by Prototaxites - tall spire-like structures that scientists have been struggling to understand since their discovery back in 1859.
These days it is generally believed that these peculiar spires were actually giant mushrooms.
"A 6-meter fungus would be odd enough in the modern world, but at least we are used to trees quite a bit bigger," said geophysicist C. Kevin Boyce of the University of Chicago in Illinois. "Plants at that time were a few feet tall, invertebrate animals were small, and there were no terrestrial vertebrates."
"This fossil would have been all the more striking in such a diminutive landscape."