Deciphering interfungal relationships in the 410-million-yr-old Rhynie chert: Sporocarp formation in glomeromycotan spores

Fungi today enter into relationships with other fungi in many ways. Although this was likely also the case in the geologic past, detailed descriptions of interfungal associations and interactions based on fossils remain scarce. Sporocarps bounded by a peridium-like envelope occur singly within the lumen of large glomeromycotan spores (Palaeomyces gordonii var. major) from the Lower Devonian Rhynie chert. The envelope consists of multi-branched, interlacing hyphae. At the tips of hyphae extending from the envelope into the lumen are produced spheroidal to urn-shaped spores. Similar sporocarps are found in several present-day species in the Glomeraceae. Clusters of spores, superficially resembling sporocarps, may also form within dead spores from any member of the Glomeromycota, including non-sporocarpic groups such as Ambispora, Acaulospora, and the Gigasporaceae, probably because they provide a shielded or otherwise advantageous environment for sporulation. The sporocarps in P. gordonii var. major from the Rhynie chert provide important information for reconstructing the numerous levels of fungal associations and interactions that existed in early continental ecosystems.