Reconstructed tree fern Alethopteris zeilleri (Carboniferous, Medullosales)

From a smaller open-pit area in the roof shale of the basal Cantabrian coal seam in Sydney Coalfield, Cape Breton Island, Nova Scotia, Canada, large amounts of the pteridosperm foliage Alethopteris zeilleri (Ragot) were found. This foliage is associated with abundant, naked medullosalean axes and dichotomies of varying sizes, up to 0.80-m long, cauline structures 0.90 m and 1.3 m long, detached ovules assigned to Pachytesta incrassata Brongniart, rare male-pollen organs of the type Dolerotheca Halle, rooted tree ferns in life position, and one specimen each of a juvenile medullosalean frond and root mantle. The fossils are compression/impression-preserved, and the foliage yielded thickly cutinized cuticles with unoriented cells (57–103 by 27–57 μm) in intercostal fields. Ultimate rachises, and abaxial surfaces (excluding costal fields) show a mixture of simple and complexly-branched trichomes, and two different structural bases. These, together with fractal dimensionality of curvatures of anticlinal walls in intercostal fields, have taxonomic potential for alethopterids.The finds suggest reconstructing A. zeilleri (Ragot) as a tree, 5–7 m high, that bore both P. incrassata Brongniart and Dolerotheca-type fructifications. Its habitat was low-land coastal plains in the Pennsylvanian coal swamps of ancestral Sydney Coalfield.