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Recent discoveries at Joggins, Nova Scotia have altered our understanding of the Pennsylvanian tropical biome. Of particular signicance has been the recognition of seasonal dryland ecosystems, compositionally distinct from the peat-forming wetland rainforests. Here I describe two anatomically-preserved fossil plant specimens from dryland alluvial plain facies. The rst specimen, Mesoxylon cf. sutclif i, is previously unknown from Joggins. It is a septate cordaitalean axis with mesarch leaf traces and a non-sympodial vasculature. Where found as isolated blocks, the secondary xylem of this plant has previously been classied as Dadoxylon recentium. The axis exhibits subtle growth interruptions suggestive of tropical rainfall seasonality, while associated traumatic zones may record re-damage. The second specimen is a Dadoxylon stump rooted within well-drained oodbasin soils. It conrms earlier conjecture, based on parautochthonous assemblages, that cordaitalean trees grew in inter-channel areas. Together these new specimens improve our knowledge of the composition and ecology of seasonal dryland vegetation at Joggins. RESUME Des decouvertes recentes a Joggins (Nouvelle-Ecosse), ont modie notre comprehension du biome tropical pennsylvanien. La reconnaissance d'ecosystemes de milieux arides saisonniers aux compositions distinctes des forets tropicales humides ayant forme des tourbieres, s'avere particulierement importante. Je decris aux presentes deux specimens preserves de plantes fossiles anatomiquement provenant du facies d'une plaine alluviale de milieu aride. Le premier specimen, un Mesoxylon cf. sutclif i, etait auparavant inconnu a Joggins. Il s'agit d'un axe cordaitaleen cloisonne comportant des cicatrices foliaires a arc moyen et une vasculature non sympodiale. Lors de sa decouverte sous forme de blocs isoles, on avait precedemment classie le xyleme secondaire de cette plante en tant que Dadoxylon recentium L'axe presente des interruptions de croissance subtiles evoquant des chutes de pluie tropicales saisonnieres, tandis que les cernes traumatiques associes pourraient temoigner de dommages causes par le feu. Le second specimen est une souche de Dadoxylon qui plongeait ses racines a l'interieur des sols d'un bassin de crue bien draine. Il conrme une conjecture anterieure, basee sur des assemblages parautochtones, supposant que les arbres cordaitaleens aient pousse dans des secteurs situes entre des chenaux. Ces deux nouveaux specimens ameliorent notre connaissance de la composition et de l'ecologie de la vegetation saisonniere des milieux arides a Joggins. [Traduit par la redaction.]

Anatomically-preserved cordaitalean trees from Lower Pennsylvanian (Langsettian) dryland alluvial-plain deposits at Joggins, Nova Scotia