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Artist’s depiction of the possible appearance of Prototaxites, from 400 million years in the past.(Image credit: Matt Humpage)ShareShare by:
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Researchers suggest that a peculiar, primeval life form, considered the original colossal organism to inhabit land, may be part of a completely unknown division of the tree of life.
These entities were huge, with certain kinds achieving heights of up to 26 feet (8 meters) and widths of 3 feet (1 m). Known as Prototaxites, they existed around 420 million to 375 million years prior, during the Devonian epoch, and had the form of branchless, tube-shaped tree stems.
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However, according to findings from a study revealed Wednesday (Jan. 21) in the journal Science Advances, Prototaxites may not have actually been a gigantic fungus — rather, it could have represented a totally distinct and unfamiliar — and now defunct — form of life.
“They constitute life, albeit not life as recognized today, exhibiting structural and compound traits unlike those of fungal or plant life, and thereby constituting an entirely extinct evolutionary division of life,” as stated by study lead co-author Sandy Hetherington, a research associate affiliated with the National Museums Scotland and senior lecturer with the School of Biological Sciences at the University of Edinburgh.
Every living thing on Earth is arranged among three realms — bacteria, archaea, and eukarya — with eukarya encompassing all multicellular creatures within the four domains of fungi, animals, plants, and protists. Bacteria and archaea solely include single-celled organisms.
Prior substance breakdown of Prototaxites remains implied that they seemingly subsisted on rotting organisms, akin to numerous current fungi, rather than synthesizing their sustenance from aerial carbon dioxide like plants.
Nonetheless, as per this recent research, Prototaxites might genuinely have been a constituent of an entirely different kingdom of life, separate from fungi, plants, animals, and protists.
The researchers scrutinized fossilized residues belonging to a Prototaxites variety dubbed Prototaxites taiti, discovered intact within the Rhynie chert, which is a sedimentary accumulation of notably well-preserved relics of ancient land plants and creatures in Scotland. This variety was considerably smaller compared to several others from Prototaxites, only reaching heights of several inches, though it continues to be the largest Prototaxites specimen documented in this vicinity.
The 410 million-year-old fossil, Prototaxites, that was unearthed in Rhynie, Aberdeenshire.
Upon investigating the internal arrangement of the petrified Prototaxites, the scientists discerned that its interior encompassed a sequence of conduits, analogous to those detected within a fungus. Yet, these conduits branched and intertwined in manners quite dissimilar to those observed within contemporary fungi.
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“We document that Prototaxites taiti fossils originating from the 407-million-year-old Rhynie chert possessed unique chemical features from those of synchronous Fungi and unique structural traits from every recognized Fungi,” the researchers penned in their study. “This outcome casts doubt upon Prototaxites’ fungal connection, alternatively recommending that this enigmatic organism be most suitably assigned to an utterly extinct eukaryotic lineage.”
Authentic fungi hailing from the same period have similarly been preserved within the Rhynie chert, enabling the scientists to chemically analyze them against Prototaxites. Aside from their singular structural traits, the team discovered that the Prototaxites remains left behind chemical signatures entirely distinct from those of the fungal remains, hinting that Prototaxites lacked chitin, a prominent ingredient of fungal cell walls and a distinct characteristic of the fungal domain.
Reconstruction portraying the possible paleoenvironment of the Rhynie Chert more than 400 million years ago.
Conversely, the Prototaxites remains appeared to encompass chemicals analogous to lignin, a compound present within the wood and bark of plants.
Kevin Boyce, a professor employed at Stanford University, steered the 2007 study postulating Prototaxites as a gigantic fungus and remained uninvolved with this current research. However, he communicated with New Scientist, conveying his concurrence with the study’s findings.
“Considering the phylogenetic insights presently available, there is no suitable location to place Prototaxites within the fungal phylogeny,” Boyce stated. “Hence, it may be a fungus, though regardless of being a fungus or something entirely unrelated, it signifies an unprecedented experiment encompassing complex multicellularity that has since gone extinct and shares no multicellular common forebear with any extant organism.”
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Supplementary investigation into Prototaxites remains must be carried out to ascertain whether they constituted fungi or a wholly separate variety of life, and to deduce the cause of their extinction occurring millions of years ago.
“The Rhynie chert is remarkable. It is among the planet’s most ancient fossilised terrestrial ecosystems, and due to the preservation excellence and organism diversification, we are enabled to pioneer groundbreaking methods such as machine learning upon fossil molecular information,” voiced study initial author Corentin Loron, a researcher assigned to the U.K. Centre for Astrobiology situated at the University of Edinburgh. “Considerable additional material originating from the Rhynie chert resides within museum assortments earmarked for comparative studies, potentially contributing substantial context to scientific outcomes.”
Editor’s note: Initially, this article was disseminated in March 2025, succeeding the study’s availability on the preprint server bioRxiv; its revision occurred on Jan. 22 upon the peer-reviewed publication of the study.
Article Sources
Prototaxites fossils are structurally and chemically distinct from extinct and extant Fungi. Sci. Adv.12,eaec6277(2026).DOI:10.1126/sciadv.aec6277
Jess ThomsonLive Science Contributor
Jess Thomson acts as a freelance journalist. Her prior engagement encompassed operating as a science correspondent for Newsweek, coupled with authorship for outlets such as VICE, The Guardian, The Cut, and Inverse. Jess possesses a Biological Sciences degree from the University of Oxford, with specialization in animal behavior and ecology.
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