Prototaxites: The Giant Life Form That Was Not a Fungus

Prototaxites grew up to 8 meters tall and 1 meter wide, and new evidence suggests this giant Devonian organism was neither a plant nor a fungus.

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Hundreds of millions of years ago, long before familiar forests dominated the land, Prototaxites produced enormous trunk-like structures that could reach about 8 meters tall and roughly 1 meter wide. Fossils show that these organisms were built from tightly interwoven microscopic tubes and could tower above the other vegetation of their time. For more than a century, Prototaxites was commonly interpreted as a giant fungus, although its exact identity has remained controversial. Researchers have also proposed connections to lichens and other ancient forms of life. Recent work has strengthened the case that Prototaxites does not fit comfortably within either modern or known extinct fungi. A 2026 study comparing exceptionally preserved Prototaxites fossils with fungi from the same ancient environment found important structural and chemical differences, leading the researchers to propose that Prototaxites belonged to an entirely extinct lineage of eukaryotic life. That does not mean scientists have discovered a living fourth kingdom or settled every detail of its biology. Instead, the fossils remain evidence of a remarkably unusual branch of ancient life whose exact place in the tree of life is still being investigated.

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