An unusual specimen of the enigmatic fungal reproductive unit Windipila spinifera from the Lower Devonian Rhynie cherts of Scotland

Windipila spinifera from the Rhynie cherts is a spheroidal microfossil enveloped in a hyphal mantle from which extend prominent spines and otherwise shaped projections. It is believed to be a reproductive unit of a fungus in the Glomeromycota or zygomycetes, but features to determine the systematic affinities have not hitherto been documented. This study describes a new specimen of W. spinifera that contains a single spherical structure from which a hypha arises that extends outside and terminates in what appears to be a sporangium. The specimen is reminiscent of germinated zygospores of the germ-sporangial type, and thus may suggest affinities of W. spinifera to the zygomycetes. However, the interior sphere and its outgrowth could also be a part of another organism that had invaded W. spinifera .