A new look at the permineralized flora of Grand-Croix (Late Pennsylvanian, Saint-Etienne basin, France)

A survey of the anatomically preserved flora of the Grand-Croix cherts (Late Pennsylvanian, Saint-Etienne basin, France) is presented following a study of collections preserved in the Swedish Natural History Museum, Stockholm in complement to previous investigations on the original material kept in France. An exhaustive list of the flora is provided, confirming the particular importance of this permineralized plant assemblage that is one of the most diverse for the Late Pennsylvanian. The observed occurrence of taxa and organs confirms a previous quantitative study based on material in the French collections: cordaiteans are both the most common taxa and the most important contributors to peat volume, whilst leaves are the most common and abundant organs. However, the seed ferns are the most diverse group of plants before cordaiteans and ferns; the exceptional diversity of medullosan ovules is of particular interest. The Grand-Croix flora is compared with that of the nearby Early Permian basin of Autun. The two assemblages have 21 genera, but only 6 species, in common, and this may be explained by differences in age and taphonomy. The Grand-Croix flora is also similar to that of American coal balls of the same age and, despite taxonomic differences, it is significant that several species of ferns and seed ferns are common to the vegetation of the French limnic and American paralic basins.