The first anatomically preserved wood specimens of an upland Carboniferous flora from the Iberian Peninsula are reported from the Erillcastell Basin (Eastern Pyrenees, Catalonia, Spain). Two taxa are described, a calamitacean Equisetale (Arthropitys sp.) and a Cordaitale (Dadoxylon sp.). The Arthropitys specimen shows fusiform multiseriate rays composed of square parenchyma cells with conspicuous uniseriate or multiseriate simple pits. These pits are located near the transverse walls and occasionally in the tangential walls. The tracheids vary in lumen size, with scalariform-bordered pits on their radial walls and multiseriate pits in their cross-field areas. The Dadoxylon specimen commonly has uniseriate fusiform rays. The tracheids are long, with a square shape in transverse section. Their radial walls bear araucarian pitting with a uni- to triseriate arrangement. The pits are circular with a spindle-shaped aperture. Comparison of the Erillcastell specimens with coeval species from Europe indicates that they could belong to new species. The good preservation of the new fossil wood yields significant palaeoenvironmental information. The lack of marked growth rings in both specimens and the presence of tyloses in Dadoxylon suggest that the climate in the intramontane basins of the Pyrenees was slightly seasonal towards the end of the Carboniferous. This contrasts with the marked seasonality of coeval lowland basins. Such upland habitats may have enhanced the survival of plants adapted to humid conditions in a global context of increasing aridity.

Two specimens preserved in silica from the late Pennsylvanian were found in Erillcastell. Ten thin sections about 30 µm thick were prepared in the transverse, radial, and tangential planes. They are stored in the Museu de Ciències Naturals de Barcelona with the collection numbers MGB90407.1-MGB90407.3; MGB90408.1-MGB90408.7. The slides were photographed with a Keyence VHX-7000 digital microscope. The measurements were taken for each wood character using the free software “ImageJ” (https://imagej.net/Welcome).