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

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.