An article on the Smithsonian Institution’s blog describes gigantic fungi that dominated the Earth’s biota 400 million years ago. Originally these fossil mushrooms were thought to be primitive conifer trees, or enormous liverworts, but spectral analysis has shown they did not use photosynthesis and were probably members of the kingdom of fungi.
This fossil, designated Prototaxites, has been found in many places around the world, notably in Quebec and the Middle East. 24 feet tall and 3 feet wide, they towered over the earliest primitive trees.
Here’s a picture of one being dug up in Saudi Arabia. Now THAT’s a mushroom… Fun to speculate whether they tasted good, and if they still exist on some forgotten Jurassic Park island!