Some 115 million years ago, on the ancient supercontinent Gondwana, a small mushroom dropped into a river and washed away into a salty lagoon, where it was buried in sediment and lost to the ages. After stumbling across the remains of this Cretaceous fungus in Brazil, researchers say it's the oldest fossilized mushroom in the world.
Paleontologist Sam Heads, who specializes in fossilized insects, was digitizing specimens from the Crato Formation when he found an orangey-brown something-or-other that got him wondering about what it was, he told me. "I looked at it under the microscope, and I could see structures that looked like gills. It has a cap and a stem," said Heads, who's based at the Illinois Natural History Survey. "I thought, wow. This looks like a mushroom."
Finding dinosaur bones that date back millions of years is one thing. But discovering a mushroom from the Early Cretaceous, when the Earth teemed with dinosaurs and flowering plants were beginning to emerge, is astounding. "Mushrooms are very ephemeral in nature," Heads told me over the phone. "Quite often, they're gone within a matter of days."
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Yet this mushroom hung around for millions of years, thanks to the environment where it was preserved. "There are only about 10 fossilized mushrooms known," Heads said. All the others are preserved in amber, as tree resin dripping down to the ancient forest floor encased and preserved them. (The second-oldest is about 100 million years old, according to him.)
"The Crato Formation is really unique in terms of exceptional preservation," Heads continued, as this ancient mushroom goes to show. His research, with co-author Andrew Miller, an expert in ancient plants and fungi, is described in a new paper in PLOS ONE.
So, was this mushroom edible, or toxic? Would dinosaurs have chowed down on this fungus, or avoided it? All that, for now, is impossible to say. According to Heads, he and Miller stopped short of assigning it to a family of mushrooms, because they couldn't be sure. (However, they speculate it may have been something like mushrooms from the family Strophariacae.)
"I've been working on the Crato Formation for 15 years now," Heads said. "I'd never seen something like this before. But this specimen shows it's possible."