Five dispersed medullosalean male organs, one species? Late Pennsylvanian Sydney Coalfield, Canada


Authors: Zodrow EL, Pšenička J

Published in: Bulletin of Geosciences, volume 96, issue 1; pages: 29 - 51; Received 14 February 2020; Accepted in revised form 20 August 2020; Online 29 November 2020

Keywords: compression, seed fern, male organs, micromorphology, taphonomy,

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Five dispersed medullosalean male-organ compressions are embedded within a few centimeters of each other in basal Cantabrian fluviolacustrine sediments, Sydney Coalfield, Canada. Exposed are variable shapes, surface features and apparent sizes. The paper deals with the cause of the repose differences, and if one organ species was preserved in five differing positions, or conversely, if five species are involved. New insights based on the macerated external cover (theca) include soluble multicellular trichomes in en echelon formation that are interspersed with rare heteromorphic stomata, and imbricated pattern of prepollen sacs on the internal layer. The organs are interpreted as synangiate structures with large ellipsoidal/circular monolete prepollen grains (overall 447 × 320 μm average, n = 150) of Monoletes Ibrahim ex Schopf. Based on observational data, it appears that all organs belong to one biological species and the enormous size range of prepollen grains could express natural variability, where the huge grains are associated with tripartite segmentation and the smaller grains with quadripartite segmentation in Dolerotheca Halle. The anatomical positions of diverse cuticular and acellular fragments could not be ascertained in the organs. The proximal, distal, or lateral resting positions, relative to the bedding plane of deposition, are haphazard. The studied organs compare with Dolerotheca, although specific assignment is deferred because of an unresolved anatomy in these compressions. The discovery of these five specimens, in concert with previous discoveries, strengthens the hypothesis of an organic connection with Alethopteris pseudograndinioides.