“Cast a net back 450 million years ago to the Ordovician Era, and you wouldn’t capture anything more than the ancestors of millipedes and worms. However, you might notice tall 29-feet-tall (8 meters) trunks without branches or leaves, towering over a landscape of newly-evolved vascular plants. These trunks, which have been found as fossils all over the world, are now strongly believed to be mushrooms—giant fungal towers that mean the kingdom of fungi produced the first giant land organism.”—”Long Before Trees Overtook the Land, Our Planet Was Covered by Giant Mushrooms”

See “Mystery prehistoric fossil verified as giant fungus“—”Scientists have identified the Godzilla of fungi – a giant, prehistoric fossil that has evaded classification for more than a century. A chemical analysis has shown that the 6-metre-tall organism with a tree-like trunk was a fungus that became extinct more than 350 million years ago. Known as Prototaxites, the giant fungus has intrigued scientists, who originally thought it was a conifer. In 2001, Francis Hueber at the National Museum of Natural History in Washington DC, US, first suggested it may be a fungus, based on an analysis of the fossil’s internal structure. But he had no conclusive proof. ‘No matter what argument you put forth, people say it’s crazy,’ says C. Kevin Boyce, a geophysicist at the University of Chicago in Illinois, US. ‘A 6-metre-fungus doesn’t make any sense, but here’s the fossil.’ Boyce, who says Prototaxites ‘get his vote for being one of the weirdest organisms that ever lived”, helped solve the mystery by comparing the types of carbon found in the giant fossil with plants that lived about the same time, some 400 million years ago.'”

Reminds me of some J Augustus Knapp illustrations for Etidorhpa by John Uri Lloyd.