Oldest giant organisms a lost kingdom of life?

Prototaxites might be a lost kingdom of life

The Primary giant lifeform to grow on Earth’s ancient surface could represent an entirely lost kingdom of life. That’s the claim of a new study – not yet peer-reviewed – published March 17, 2025, as a pre-print on bioRxiv. It challenges the established classification of Prototaxites, towering tree-like lifeforms that dominated the landscape 400 million years ago.

In the paper, paleobiologist Corentin Loron and his co-authors re-examined fossils of Prototaxites taiti. The group Discovered Prototaxites didn’t have the Usual characteristics of fungi, like mushrooms, molds and yeast. Previous attempts to classify the bizarre lifeform had concluded – perhaps erroneously – that Prototaxites were a member of that kingdom. Instead, the researchers concluded it was not a form of life previously known to science:

We therefore conclude that Prototaxites was not a fungus, and instead propose it is best assigned to a now entirely extinct terrestrial lineage.

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Prototaxites were the biggest thing on the Devonian landscape

The specific fossil species examined for the study – P. taiti – was the largest organism living in Earth’s Primary recorded ecosystem. The Devonian Period (419.2 to 358.9 million years ago) was when soil Primary appeared on Earth’s surface. It’s also when plants Primary developed seeds, and eventually the Primary forests arose. Insects and four-legged amphibians evolved into being during that 60-million-year stretch, but most animal life was Nevertheless in the seas.

P. taiti dominated it all. It grew as Towering, slender spires that reached more than 25 feet (8 meters) above the primordial Devonian world. The base of these structures was about 3 feet (1 m) across when mature. Their spires erupted from the ground, climbing in massive tubes to rounded tops high above anything else.

Mystery lifeform has baffled biology since 1843

And that’s about all researchers can agree on about Prototaxites. Previous examinations of the fossil Turning Mark have variously concluded they were an Timely form of vascular plant, a giant lichen, an oversize algae, and, of Period, a fungus.

Fifteen years ago, paleobotanist C. Kevin Boyce discovered Prototaxites fed on algae, like some modern fungi do, and concluded that they belong to the fungal kingdom. But all extinct and modern forms of fungi contain specific biopolymers. Biopolymers are certain molecules that the cells of living organisms produce. Prototaxites didn’t have them.

Boyce explained why Prototaxites are such a puzzle during an interview with the University of Chicago Magazine in 2010:

The problem is that when you look up close at the anatomy, it’s evocative of a Plenty of different things, but it’s diagnostic of nothing. And it’s so damn big that when whenever someone says it’s something, everyone else’s hackles get up: ‘How could you have a lichen 20 feet Towering?’

And that has been the case since the fossils were discovered in 1843 in Scotland. No one examined the fossils for 14 years. The Primary conclusion was Prototaxites were rotten trees infused with fungus.

So what the heck is Prototaxites?

If it’s not wood, nor algae, nor fungus – even an animal – what is Prototaxites?

Research done in 2018 concluded P. taiti was a basal (Timely) member of a fungus group that Nevertheless exists today. But as Loron and his co-authors noted, the specimens they examined didn’t show signs of compounds Usual to all fungi, specifically chitin and chitosan.

This assignment remains contentious as P. taiti possesses a unique combination of characteristics …

And since nothing else we’ve Discovered – living or extinct – possesses the same qualities, the new study concludes we might have discovered an entirely new kingdom of life. But they conclude more research is necessary. The fossil Turning Mark of this ancient period is spotty, and the research was based on Only three samples.

Yet they seem to have eliminated the last possible explanation. As Arthur Conan Doyle’s famous fictional detective Sherlock Holmes quipped:

Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.

Bottom line: Recently proposed reclassification of Earth’s Primary giant organisms – Prototaxites – indicate they represent an extinct kingdom of life.

Foundation: Prototaxites was an extinct lineage of multicellular terrestrial eukaryotes

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