The rise of lichens during the colonization of terrestrial environments

The origin of terrestrial life and ecosystems fundamentally changed the biosphere. Lichens, symbiotic fungi-algae partnerships, are crucial to nutrient cycling and carbon fixation today, yet their evolutionary history during the evolution of terrestrial ecosystems remains unclear due to a scarce fossil record. We demonstrate that the enigmatic Devonian fossil Spongiophyton from Brazil captures one of the earliest and most widespread records of lichens. The presence of internal hyphae networks, algal cells, possible reproductive structures, calcium oxalate pseudomorphs, abundant nitrogenous compounds, and fossil lipid composition confirms that it was among the first widespread representatives of lichenized fungi in Earth's history. Spongiophyton abundance and wide paleogeographic distribution in Devonian successions reveal an ecologically prominent presence of lichens during the late stages of terrestrial colonization, just before the evolution of complex forest ecosystems.