Diamond helps uncover a lost branch of life

Researchers studying one of palaeontology’s longest-running mysteries have shown that Prototaxites, giant column-like fossils that dominated Earth’s earliest terrestrial landscapes, do not belong to the fungal kingdom, as long suspected. Instead, new evidence suggests they represent a completely distinct and now extinct branch of complex eukaryotic life. 

The findings, published in Science Advances, were supported by experiments carried out on Diamond’s B22 infrared microspectroscopy beamline. 

Prototaxites fossils date back more than 400 million years to the early Devonian period and could reach several metres in height, making them the largest known organisms on land at the time. They are typically preserved as massive, trunk-like columns found in some of the earliest terrestrial ecosystems, long before trees had evolved. For over 160 years, scientists have debated their biological identity, with fungi long considered the most likely explanation due to their tubular internal structure and lack of obvious plant features.

This new study combined high-resolution structural observations with advanced chemical analyses to reassess that assumption - and found that Prototaxites does not match fungi, living or extinct. Instead, the results point to a form of complex multicellular organisation unlike any known group, suggesting that early life on land included major lineages that have since disappeared.

Diamond’s role: chemical fingerprints at the microscale

Researchers from the University of Edinburgh used infrared microspectroscopy to probe the molecular composition of Prototaxites fossils at high spatial resolution. Lead author Dr Corentin Loron, as well as postgraduate students Edwin Rodriguez Dzul and Ruaridh Alexander used this technique to identify specific chemical bonds and functional groups within complex samples. Spectral similarities between different types of structures within the sample supported the hypothesis that the specimen was a single organism and not a symbiotic association of different organisms.

Artist impression of what Prototaxites would have look like. (credit Matt Humpage)

Beyond the chemical differences, the fossil's internal architecture was shown to differ fundamentally from fungal hyphal networks. The fossil is made of many different tiny tubes, and detailed 3D imaging shows that they all branch and connect into one tightly linked internal network - something unlike any known fungus.

Machine-learning comparison of spectroscopic data with  equivalent data from a wide range of modern and fossil organisms,  consistently placed Prototaxites outside all known major groups.

The authors conclude that Prototaxites represent a unique evolutionary experiment in large, multicellular life, belonging to a lineage that has no modern equivalent.

The discovery reshapes our understanding of early terrestrial ecosystems, showing that Earth’s first complex land environments were populated by organisms unlike anything alive today. It also highlights the growing role of synchrotron techniques in palaeontology, where subtle chemical signals preserved in fossils can unlock deep evolutionary insights. 

By enabling detailed, non-destructive chemical analysis of rare fossil material, Diamond continues to play a crucial role in revealing the hidden biology of ancient life.