Deciphering interfungal relationships in the 410-million-yr-old Rhynie chert: Rhizophydites shutei sp. nov. (fossil Chytridiomycota) on glomeromycotan acaulospores

Michael Krings

Pages	77–89
DOI	10.37520/fi.2024.008
Keywords	apophysis, discharge papilla, Glomeromycota, Early Devonian, rhizoidal system, Rhizophydium, zoosporangium
Type of Article	Peer-reviewed
Citation	KRINGS, Michael. Deciphering interfungal relationships in the 410-million-yr-old Rhynie chert: Rhizophydites shutei sp. nov. (fossil Chytridiomycota) on glomeromycotan acaulospores. Fossil Imprint / Acta Musei Nationalis Pragae, Series B – Historia Naturalis. Prague: National Museum, 2024, 80(1), 77–89. DOI: https://doi.org/10.37520/fi.2024.008. ISSN 2533-4050 (tisk), 2533-4069 (online). Also available from: https://www.nm.cz/en/periodicals/fossil-imprint-acta-musei-nationalis-pragae-series-b-historia-naturalis/80-1/deciphering-interfungal-relationships-in-the-410-million-yr-old-rhynie-chert-rhizophydites-shutei-sp-nov-fossil-chytridiomycota-on-glomeromycotan-acaulospores

Fossil Imprint / Acta Musei Nationalis Pragae, Series B – Historia Naturalis | 2024/80/1

The spores of arbuscular mycorrhizal fungi (Glomeromycota) in the Early Devonian Rhynie ecosystem served as a habitat for a diversity of other fungi, only a few of which have been studied in detail so far. Rhizophydites shutei nov. sp. occurs in planar assemblages and tuft-like clusters comprised of thalli in various stages of development on Archaeosporites rhyniensis-like acaulospores. The presence of multiple individuals on several closely spaced hosts allows a thorough depiction of this fungus. Thalli are monocentric and characterized by an ovoid, narrowly to broadly citriform, bulb-shaped, or globose inoperculate zoosporangium 10–35(–38) μm high and 7–33 μm wide, and an endobiotic rhizoidal system reaching into the host lumen. The sporangium can be epibiotic or interbiotic (stalked), or located between the wall layers of the host spore. Mature sporangia have a pronounced apical papilla. Similarities with the modern chytrid genera Rhizophydium and Phlyctochytrium are used to suggest that the fossil belongs to the Chytridiomycota, and to place it in the genus Rhizophydites, which accommodates chytrid-like fossils that are morphologically similar or even identical to present-day Rhizophydium. This discovery contributes to our understanding of the various roles mycorrhizal fungi had in early terrestrial ecosystems.

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