Permineralized coniferophytes from the Autun Basin: specimens from two new localities of Renault zone 3

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Английский. Four zones yielding silicified plant remains have been recognized in the Autun Basin by Renault (1893-1896). Zones 2, 3 and 4, characterized by Autunian plants, correspond to the successive formations of Igornay and Muse (lower Autunian), and Surmoulin-Millery (upper Autunian). Their paleobotanical content, together with that preserved as adpressions in the same formations, document paleofloral changes on the western side of the Tethys within a time interval extending from the latest Ghzelian (uppermost Pennsylvanian) to the early Sakmarian (lower Permian) (Broutin et al. 1999). The analyses realized so far indicate a progressive replacement of wetland plants by taxa better adapted to drier environments. The number of taxa referable to the Coniferophytes (i.e. belonging to the Cordaitales and Coniferales) increased during this time interval.In order to enlarge the record of permineralized plants from the Autun Basin and improve our understanding of their diversity patterns, prospections directed in 2011 by Jean-Luc Desage, and 2015 by Georges Gand, were conducted on the northwestern side of the village of Muse. Isolated fragments representing coniferophytic woods were collected in two new localities, one along the banks of the Arroux River, the second at Les Echars. Both localities fall in Renault’s zone 3. We present here the main characters of these specimens and compare them to Cordaixylon sp., Dadoxylon rollei and Scleromedulloxylon varollense, the three taxa of coniferophytic affinities found to date in zone 3 (Broutin et al. 1999). Many specimens show large spherical structures scattered in either rays or tracheids. They measure about 100 μm wide and show heavily silicified walls. The cells surrounding them are compressed, indicating that these structures developed inside living trees. Based on wood characters alone, the new discoveries confirm that the community of coniferophytic trees was well established in the Muse formation but suggest that it may not have been highly diversified.