Ever since their discovery more than 165 years ago, massive fossilized structures left by an organism known as *Prototaxites *have proven impossible to categorize.
Researchers in the UK have suggested in a recently published study that there’s a very good reason these oddities don’t fit neatly on the tree of life – they belong to a branch all of their own, with no modern equivalent.
Some 400 million years ago, the swamps of the late Silurian period would have sprouted a mix of horsetails, ferns, and other prototype plants that look…
Ever since their discovery more than 165 years ago, massive fossilized structures left by an organism known as *Prototaxites *have proven impossible to categorize.
Researchers in the UK have suggested in a recently published study that there’s a very good reason these oddities don’t fit neatly on the tree of life – they belong to a branch all of their own, with no modern equivalent.
Some 400 million years ago, the swamps of the late Silurian period would have sprouted a mix of horsetails, ferns, and other prototype plants that look positively alien today.
Related: Stunning Grand Canyon Fossils Reveal Evolution’s Weird Experiments
Among them stretched 8-meter (26-foot) tall towers that defy easy identification. Wide and branchless, these organisms may have been a form of algae or ancient conifer, researchers suspect, based on what little evidence remains.
Fossils found on the shores of Gaspé Bay in Quebec, Canada, were initially considered by geologist John William Dawson to be the remains of rotting trees, leading to his naming it ‘first conifer’ back in the 1850s.
A confocal laser scanning microscopy image revealing the microstructure of a Prototaxites fossil. (Laura Cooper/BlueSky)
Though the name stuck, confusion over the fossil’s classification continued until National Museum of Natural History paleontologist Francis Hueber confirmed in 2001 that Prototaxites was indeed most likely an enormous fungus.
That conclusion was backed up years later in 2017 by a subsequent analysis of a fossil fragment assumed to be from the peripheral region of a smaller Prototaxites species named P. taiti.
The 2017 study claimed to identify textures that resembled the fertile structures of today’s Ascomycota fungi.
Magnified image of a thin section showing characteristic tubes and medullary spots of P. taiti. (Loron et al., Science, 2026)
Not everybody is convinced, however, given the possibility that the distinct fragments might not have even been connected.
Related: Newly Discovered Organism Could Represent a Whole New Branch in The Tree of Life
"In the books and books of anatomy written about living fungi, we never find structures like that," University of Edinburgh paleobotanist Alexander Hetherington told Erik Stokstad at Science Magazine.
Hetherington co-led a study on three different P. taiti fragments, concluding there’s insufficient evidence to conclude Prototaxites is a fungus at all.
Comparisons between Prototaxites fossils and other organisms put it into a group of its own. (Loron et al., Science, 2026)
Through a review of microscopic anatomy and chemical analysis of its tubular structures, the team of researchers systematically eliminated each and every candidate group, leaving no modern organism with which it might share some kind of ancestral relationship.
More in Science
Fungi? Rejected thanks to the unique way its anatomy connects.
A plant or algae? Not likely given its chemical composition.
A mix of the two, such as a lichen? Not with that anatomy.
Some bizarre animal? Cell walls say no chance.
Audition now for ScienceAlert’s Casting Call
"Based on this investigation we are unable to assign Prototaxites to any extant lineage, reinforcing its uniqueness," the researchers claim.
"We conclude that the morphology and molecular fingerprint of P. taiti is clearly distinct from that of the fungi and other organisms preserved alongside it in the [Devonian deposit], and we suggest that it is best considered a member of a previously undescribed, entirely extinct group of eukaryotes."
Related: Complex Life May Be a Billion Years Older Than We Thought
What might have happened to this long-dead group of organisms is anybody’s guess. Further reviews may even return the mystifying group back to its box among ancient fungi.
Without similar specimens to relate them to, Prototaxites may simply remain a fossil anomaly – a reminder that evolution is a constant experiment, one littered with far more failures than we may ever have realized.
This research was published in Science.
An earlier version of this article was published in March 2025 before the research was peer-reviewed.