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General palaeontology, systematics and evolution (Palaeobotany) The fern Stauropteris oldhamia Binney: New data on branch development and adaptive significance of the hypodermal

a b s t r a c t Well-preserved specimens of Stauropteris oldhamia are described. The material was col- lected in the early 1920s from the Lower Westphalian (Early Pennsylvanian) Saurue seam from Belgium. The fossil plants occur as permineralized axes fragments within a coal ball. This study confirms most of the interpretations made by previous researchers. The obser- vation of immature axis however suggests a less regular organization than previously interpreted beyond the three first branching orders. We also highlight the presence of pro- fusely and dichotomously branched aphlebiae, the lack of laminate organs as well as the presence of hypodermal aerenchyma in all plant parts. We interpret these features as part of a very specialized assimilatory apparatus indicating an adaptation to a humid swamp