Michael Krings, Benjamin Bomfleur, Hans Kerp
Abstract The Lower Devonian Rhynie cherts contain a wide variety of microfossils with possible affinities to fungi or fungus-like organisms, only a fraction of which have been described and critically evaluated. Philophrosyne beckeri gen. et sp. nov. occurs in accumulations of decayed plant parts interspersed with patches of microbial-mat communities. The specimens consist of a sac-like envelope with a diameter of 30–50 µm, filled with closely spaced spherules of equal or varying sizes with a diameter of up to 25 µm. In some specimens, a tubular subtending hypha is preserved, which either originates from a plant fragment or emerges from a microbial mat. The fossil is interpreted as an oomycete oogonium containing oospores, as small, club-shaped structures found on several specimens are strongly reminiscent of paragynous antheridia. Modern morphological equivalents exist within the order Saprolegniales. This discovery expands our knowledge of life forms in early terrestrial ecosystems that closely resemble modern oomycetes.