A microfossil with suggested affinities to the Peronosporomycetes (Oomycota) from the Carboniferous (c. 330 Ma) of France

Abstract : Combresomyces cornifer is a conspicuous spheroidal microfossil (<40 μm diam.) that occurs in Mississippian (~330 Ma) chert from France and is characterized by a prominent surface ornament of antler-like extensions positioned on hollow, conical or column-like wall papillations. The fossil has been interpreted as a peronosporomycete oogonium based on appressed paragynous antheridia. Here we report Annelaurea excornis nov. gen. et sp., a new fossil from the French Mississippian chert that resembles C. cornifer in overall morphology, but is distinctly thicker-walled and lacks the antler-like extensions. Moreover, size and shape of the papillations vary greatly within one specimen. This discovery suggests that by the Carboniferous the peronosporomycetes were already a morphologically diverse group