Morphology, ultrastructure and affinity of barremian (lower cretaceous) megaspores dijkstraisporites and paxillitriletes from Brilonnehden, Germany

Abstract

A number of well‐preserved megaspores of Paxillitriletes fairlightensis (Dijkstra) Potonié & Dijkstraisporites helios (Batten) Nicholson & Hall from the terrestrial Barremian (Lower Cretaceous) of Brilon‐Nehden (Germany) have been investigated in detail using electron microscopy. Morphology and ultrastructure is compared to that of known examples of Mesozoic megaspores and this, combined with the presence of adherent monolete microspores, indicates an isoetalean affinity for both species. Furthermore, the reticulate body ornament, laesural and equatorial elaboration, and wall ultrastructure suggest a close systematic relationship between these two species. This is new evidence in support of the view that most Mesozoic and Tertiary megaspores with expanded laesural lips and/or zona belong to this order of heterosporous lycopsids.