Paleomycology

Did You Know?

• Interest in fossilized fungi dates back to the early nineteenth century.
• Paleoecologists historically focus more on plant and animal macrofossils due to difficulty identifying fungal physiology and morphology.
• The first illustrated collection of fossil fungi was curated by Luigi Meschinelli in 1898.

Early Discovery

Most fossilized fungal remains, including spores and sclerotia, are found in amber. Two significant discoveries—one in Baltic amber dated to the Eocene and another in Dominican amber dated to the Miocene—are important for comparing fungal evolution across timescales. Baltic amber preserved a hexapod alongside the fungus Aspergillus collembolorum, suggesting parasitic relationships existed as early as 34 million years ago. The presence of wood-rotting fungi in Callixylon whiteanum, one of the oldest known trees, indicates that saprophytic interactions between plants and fungi evolved when wood first developed.

Ecological Importance

Fungi require a carbon source, obtained through decomposing organic plant and animal matter. Mycorrhizal relationships are mutualistic: the fungus gains carbon while the plant receives mineral nutrients. Fungi discovered in the Early Devonian Rhynie chert, when plants were rootless and leafless, suggest fungi played a major role in plant evolution into terrestrial ecosystems. Fungal endophytes and epiphytes similarly form symbiotic relationships with plant hosts, but the absence of fossil endophytes on leaves before the Cretaceous implies leaves became a fungal habitat only after flowering plants evolved around 130 million years ago. Fossil epi- and endophytes help determine evolutionary modifications for colonizing ecosystems, identify environmental tolerances, serve as paleoclimatological proxies (e.g., Sporormiella used to reconstruct megaherbivore extinction), and reveal extinct morphologies. Bioeroder fungi have been found in carbonate substrates like shells, extracting organic carbon and indicating mutualistic or parasitic relationships. Fungal hyphae and spores in coprolites show arthropods used fungi as a food source. Fossil fungi also contribute to geological history through rock weathering and nutrient cycling in mineral media.