Dinoflagellate cysts from the Upper Cretaceous (upper Campanian to lowermost Maastrichtian) of the Middle Vistula River section, Poland

Abstract

In this article, the most representative dinoflagellate cyst genera and species recognised in the rich palynomorph assemblages of the upper Campanian–lowermost Maastrichtian succession of the Middle Vistula River section (central Poland) are treated taxonomically: in particular, six genera and 16 species are considered. Oligosphaeridium araneum sp. nov., which possesses processes with relatively long and slim stems and perforate or fenestrate terminations, is described as new. Glaphyrocysta pala comb. nov. and Hystrichosphaeridium brevispinum stat. nov. are proposed. Glaphyrocysta pala comb. nov. has a dorso-ventrally compressed central body and lacks mid-ventral processes connecting the central body with the membrane, suggesting its affinity with Glaphyrocysta, rather than Riculacysta; and H. brevispinum stat. nov. is raised to species rank on the basis of the distinct morphology of its processes. The tabulation pattern and plate arrangement are determined for the first time in Amphorosphaeridium and revised in Callaiosphaeridium. Both genera have a sexiform hypocystal configuration, L-type ventral organisation, and neutral torsion, which indicates their inclusion in the subfamily Leptodinioideae. The species-level taxonomy of the genera Hystrichosphaeridium and Samlandia is discussed. The transfer of Hystrichosphaeridium proprium to Hystrichokolpoma is rejected, and Hystrichosphaeridium? recurvatum is questionably left in Hystrichosphaeridium, although it is characterised by a commonly larger number of processes per plate and the lack of a preapical process.