Comment on “The ‘seed-fern’ Lepidopteris mass-produced the abnormal pollen Ricciisporites during the end-Triassic biotic crisis” by V. Vajda, S. McLoughlin, S. M. Slater, O. Gustafsson, and A. G. Rasmusson [Palaeogeography, Palaeoclimatology, Palaeoecology, 627 (2023), 111,723

Abstract

Recently, Ricciisporites Lundblad and Cycadopites Wodehouse (=Monosulcites Cookson) pollen types have been found cooccurring in Antevsia zeilleri (Nathorst) Harris pollen sacs and it was assumed that the tetrads of Ricciisporites resulted from atypical pollen developmental pathway in which the pollen grains failed to separate. The pollen grains of Cycadopites type were interpreted as normal pollen grains of a peltasperm with Antevsia zeilleri pollen sacs and Lepidopteris ottonis (Göppert) Schimper foliage, and Ricciisporites, as abnormal pollen tetrads of this parent plant. However, if it were true, the exines in the pollen grains of the two types should have something in common in the ultrastructure. Examples of aberrant pollen in living seed plants show that changes occurring in the predetermined succession of events of exine development are minor and even if they finally lead to a significantly altered mature exine, the original structural plan remains recognizable. Contrariwise, the two pollen types are too dissimilar by their exine ultrastructure as well as by the general morphology and exine sculpture. Comparison with ontogenetic data on suitable modern analogues also allows one to suppose that exines of Ricciisporites and Cycadopites developed differently, in unrelated parent plants. Another explanation should be found for the presence of Ricciisporites tetrads in these pollen sacs.