for National Geographic News
At a time when the tallest trees stood just a few feet high, giant "mushrooms" towered over the landscape.
That's the finding being reported by new a paper appearing in the May issue of the journal Geology.
The study adds to the quest to solve a long-standing scientific puzzle: the true nature of a fossil that was the world's largest organism from about 420 million to 370 million years ago.
(Related news: "Giant Fossil Rain Forest Discovered in Illinois" [April 24, 2007].)
Called Prototaxites, the mystery life-form was first reported in 1859 based on samples found in Canada.
The ancient organism boasted trunks up to 24 feet (8 meters) high and as wide as three feet (one meter).
Prototaxites was widespread—its fossils are found all over the globe.
Lead study author Kevin Boyce, of the University of Chicago, said the unidentified monstrosity was a staple in textbooks while he was still in school.
"It's fun because it's kind of a classic specimen that people have worried about for a long time," Boyce said. "It's been an outstanding question for 150 years."
Since the fossil's discovery, researchers have speculated that Prototaxites was a type of algae or lichen or even a primitive pine tree.
The idea that the fossil could have been a giant fungus first emerged in 1919.
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