Fungal reproductive units enveloped in a hyphal mantle from the Lower Pennsylvanian of Great Britain, and their relevance to our understanding of Carboniferous fungal “sporocarps”

Abstract

An assemblage of distinctive fungal reproductive units occurs in a fragment of permineralized xylem from the Lower Coal Measures (Carboniferous) of Great Britain. Specimens are spherical to irregular in outline, 70–95μm in diameter, and consist of a central cavity surrounded by an investment of tightly interlaced hyphae. Clusters of specimens may additionally be enveloped in a confluent hyphal meshwork. This complement of features is quite similar to the morphology seen in mantled zygosporangia/zygospores of certain extant zygomycetous fungi. Closely associated with several of the reproductive units are single or paired smaller spherical to elongate structures, which we interpret as apposed gametangia. This discovery represents only the third record of zygomycetous fungi from the Carboniferous. Moreover, the reproductive units resemble certain Carboniferous microfossils termed fungal sporocarps in the genus Mycocarpon, and thus indirectly support the hypothesis that the systematic affinities of these sporocarps may lie with the zygomycetous fungi.