Aspects of Permian palaeobotany and palynology. XVIII. On the morphology and ultrastructure of Potonieisporites novicus (prepollen of Late Carboniferous/Early Permian Walchiaceae)

SUMMARY The type species of the palynological form‐genus Potonieisporites, P. novicus, can be considered to represent Late Carboniferous/Early Permian conifers, assignable to the Walchiaceae of the Euramerican floral province. Morphological and ultrastructural analysis of the species falsifies earlier concepts of a monosaccate organization and the presence of a distal germinal area. The species is characterized by a monosaccoid sexine expansion, completely filled with an alveolate infrastructure. A proximal aperture is distinct, but there is no evidence of distal specializations indicative of the outgrowth of a haustorial pollen tube; the species thus qualifies as prepollen. These characters are included in an emended diagnosis for the species. A restricted concept of an exclusively walchiaceous status for the form‐genus Potonieisporites can not yet be proposed, mainly because of the lack of conclusive evidence on the botanical affinity and the morphological/ultrastructural organization of similar pollen from the Gondwana floral province.