A long time before trees ever inhabited the earth it may have been covered in giant mushrooms. These where massive in size up to 24 feet and would have doted the landscape like giant spires and existed some 420 to 350 million years ago where plants were still becoming established.
Mushrooms played important roles in colonising the surface of the earth and helped nutrients become available from minerals to allow plants to grow. What a different world it would have been imagine a forest full of giant mushrooms. It would have been an alien looking world to us.
Fossilised spirals of what are thought to be these fungi have been available for over 130 years but no one could really figure out what they where. Then in 2007 a report suggested they where members of Prototaxites species although the evidence is still inconclusive
I do not think they looked much like the picture below but you get the idea.
From around 420 to 350 million years ago, when land plants were still the relatively new kids on the evolutionary block and “the tallest trees stood just a few feet high,” giant spires of life poked from the Earth. “The ancient organism boasted trunks up to 24 feet (8 meters) high and as wide as three feet (one meter),” said National Geographic in 2007. With the help of a fossil dug up in Saudi Arabia scientists finally figured out what the giant creature was: a fungus. (We think.)