Fossil lichens from the Devonian period reveal how the fungus-algae alliance paved the way for terrestrial life.

Lichens were already widespread more than 410 million years ago, according to a new international study identifying a Brazilian fossil as one of the oldest lichens in Earth’s history.

The team used state-of-the-art X-ray imaging and other advanced techniques to examine the fossils, known as spongiophytons, from the Devonian time period (about 419.2 to 358.9 million years ago).

The study brought together more than 20 institutions and state-of-the-art facilities in Brazil, Australia, the United States, the United Kingdom and France. Results are published Science advances.

According to lead author Dr. Bruno Becker Kerber from Harvard University, the fossil shows a similar combination of fungi and algae to modern lichens. “Our results show that lichens were not trivial organisms, but key pioneers in land surface change,” he said. “They helped form the soil that allowed plants and animals to take hold and diversify the land.”

The results show that ancient lichens first evolved in the cold polar regions of the supercontinent Gondwana, in areas that correspond to modern-day South America and Africa.

ANU Professor Jochen Brooks said: “Spongiophyton is an extraordinary fossil with extraordinary preservation. It must have gone hand in hand with the preservation of organic matter.” “The tough material in simple plants is cellulose. Lichens, on the other hand, are decidedly odd—they contain the same material that makes beetles and other insects tough.

“Chitan is loaded with the element nitrogen. When we analyzed the spongiophyton, we found a huge nitrogen signal, which had never been seen before. You rarely get such a clear result, it was a eureka moment.”

According to the authors, lichens still play an important role in soil preparation, nutrient recycling, and carbon sequestration in extreme environments from deserts to polar regions. However, their origins remain obscure due to their fragile nature and sparse fossil record.

“This work shows how important it is to combine traditional methods with modern techniques,” said co-author Nathalie L. Archela of the Brazilian Synchrotron Light Laboratory. “Preliminary measurements guided us to key areas of interest, and only then could we collect 3D nanometric imaging, revealing the complex fungal and algal networks that define spongiophyton as a true lichen.”