Did Monster Morel Mushrooms Once Conquer the World?

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From Jules Verne's "Journey to the Center of the Earth"/ Available simonandschuster.com

It’s morel mushroom season!  But what if I told you that once upon a time, before the first dinosaur ever roared, there were mushrooms that were as big as palm trees! 

I’m talking about Prototaxites, a super-fungus which was once the largest land creature on the planet. 

Picture Earth during the late Silurian to late Devonian Period (i.e., 420 to 370 million years ago). This was long before the giant ferns and conifers that would father the coal fields of the world. Plants are small, timidly exploring this crazy place called “Dry Land.”   

In this proto-forest of dwarf plants, Prototaxites could be a 1 meter (3 feet) thick and almost 8 meters (26 feet) high! 

The Prototaxites were discovered first in Canada by W.E. Logan in 1843. But it was John William Dawson who would name the species fourteen years later. Dawson thought the tree was a kind of ancient pine tree (“first yew”, or Prototaxite) that had been eaten up by fungi. 

The Fungus Theory

But a century and half later, plant scientist Francis Hueber classified Prototaxites – the whole thing - as one big fungus, due to its structure and morphology. 

A few years later, a research team (including Hueber) concluded that Prototaxites was indeed a fungus, due to its variety of carbon isotopes. In plants, like today's trees, two particular carbon isotopes should be in balance because they get their food by photosynthesis. In plants and animals that eat other life-forms, the isotope ratio should vary widely. The Prototaxites’ combination of isotopes indicated that it fed on decaying organic matter, just what you would expect from a fungus. 

Of course, if Prototaxites was a large fungus, it would also need a large food supply.  But if the plant world was new and small, where would the food come from? Scientists Erik Hobbie and C. Kevin Boyce suggested that Prototaxites could have fed on “algal-derived organic matter.”  Algal mats were most likely because there weren’t many true (vascular) plants for a good compost. 
 
The Non-Fungus Theory

However, another group of researchers asserted that Prototaxites was more like a kind of liverwort, curling up with other liverworts and plants and ascending into the air. They thought that the fungus-like structure was just an associative growth with fungi and cyanobacteria, just like in some modern liverworts.
But the “monster mushroom” theory is currently in vogue.    

The Mushroom Vogue
 
Did Jules Verne know about Prototaxites?  In chapter 30 of Jules Verne’s classic “Journey to the Center of the Earth,” the heroes find themselves in “a forest of mushrooms” that had been “constructed on a gigantic scale.” 
 
Simon and Schuster’s 2008 edition of the classic has a drawing of the mushroom forest on its cover. If you eliminated the mushroom caps, you’d get a pretty good visual of Prototaxites. 

My cousin told me he was a “mushroom hunter.” I told him that you can’t call it “hunting” when the prey lacks teeth or even feet to run away.  But who could hunt Prototaxites?  Not even Mario and Luigi.

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Prototaxites, By Dawon (Public Domain), Source: Wikimedia Commons