Résumé
A new fossil water mold (Peronosporomycetes), Galtierella biscalithecae nov. gen. et sp., consisting of coenocytic hyphae occurs as an intracellular endophyte in a partially degraded specimen of the reproductive organ Biscalitheca cf. musata (Zygopteridales) from the Upper Pennsylvanian Grand-Croix cherts (Saint-Etienne Basin, France). Some hyphal tips produce small spheres that subsequently develop into ornamented, opaque-walled oogonia; amphigynous antheridia encircle the necks of several immature oogonia. Also present are ovoid structures, which may represent differently shaped oogonia, hyphal swellings, or zoosporangia. Small dome-shaped structures, probably zoospore cysts, are attached to numerous host cell walls. This discovery sheds new light on the morphology and biology of water molds in a Carboniferous ecosystem. (c) 2009 Academic des sciences. Published by Elsevier Masson SAS. All rights reserved.