Microfungi from the upper Visean (Mississippian) of central France: Chytridiomycota and chytrid-like remains of uncertain affinity

A diverse assemblage of eucarpic and apparently holocarpic chytrids, and chytrid-like remains of uncertain affinity is preserved in late Visean (Mississippian; ~ 330 Ma) cherts from Combres (Roanne area) and Esnost in central France. The evidence is primarily composed of various types of (resting) spores, as well as epibiotic and endobiotic (putative) zoosporangia that occur in/on solitary unicells, peronosporomycetous oogonia, (degrading) vascular plant tissues (i.e. xylem, periderm, cortical parenchyma), and various plant and fungal spores. Vegetative parts such as tenuous filaments or rhizomycelia in organic connection are rarely preserved. Host responses possibly linked to chytrid infection occur in the form of two different types of callosities, some with a distinct penetration canal, in lycophyte xylem and periderm, as well as in fungal spores. We suggest that the majority of chytrids and chytrid-like remains preserved in the Visean cherts belonged to a community of saprotrophic microorganisms that functioned in the decomposition of organic matter. Only a few forms appear to have been parasites. The Visean cherts from France provide a rare opportunity to examine the diversity of Chytridiomycota in a Carboniferous ecosystem.