Deciphering interfungal relationships in the 410-million-yr-old Rhynie chert: Glomites bacatus nov. sp. (sporocarp-forming Glomeromycota) and associated microfungi

The fossil record of the Glomeromycota (arbuscular mycorrhizal fungi) from the Lower Devonian Rhynie chert of Scotland includes a wide variety of spores, most of which formed singly in the axes of land plants; only a few have been reported to occur as sporocarps. The Rhynie chert also provides ample evidence that these spores were attractive as a habitat and nutritional basis for other fungi. Here, I describe a new glomeromycotan sporocarp from the Rhynie chert, Glomites bacatus nov. sp., which consists of more than 100 glomoid spores and is completely enveloped by a peridium of tightly interlacing and interlocking hyphae with vesicle-like swellings. Both the peridium and the spores of the specimens at hand are colonized by other fungi, including chytrid-like thalli comparable to Rhizophydites bicornis. Other remains associated with the sporocarps could belong to fungus-like Oomycetes. These include stalked spherules reminiscent of chlamydospores, flask-shaped structures resembling sporangia, and a putative intercalary oogonium containing two unequal-sized oospores and subtended by a hypogynous antheridium with a fertilization tube protruding into one of the oospores. This discovery expands our knowledge of sporocarpic Glomeromycota in the Rhynie ecosystem and provides further evidence for the function of these fungi as hosts for other microbial life.