The oldest fossil mushroom in the world, dating back approximately 115 million years (when the former supercontinent Gondwana was breaking), It has been found in limestone preserved mineralized in northeastern Brazil.
Before this discovery, the oldest fossil mushrooms found they had been preserved in amber, but it has mineralized: somehow it reached a very saline lagoon, sank through the stratified layers of salt water and covered itself with layers on layers of fine sediments. Finally, after a long time, their tissues were replaced by pyrite, which later became the mineral Goethite.
The finding of this fungus has been reported in a study published in PLOS ONE. Researchers have placed the fungus in the order of 'Agaricales' and have called it 'Gondwanagaricites magnificus'. As the paleontologist explains Sam Heads, from the Illinois Natural History Survey (INHS), who discovered the fungus by digitizing a fossil collection from the Crato Formation of Brazil:
Most fungi grow and disappear within a few days. When you think about it, the chances of this thing being here (the obstacles you had to overcome to get from where it grew to the lagoon, be mineralized and preserved for 115 million years) have to be tiny.
The fungus was about five centimeters (two inches) tall. Electron microscopy revealed that it had gills under its cover, instead of pores or teeth, structures that release spores and can help identify species.