The overarching aim of this thesis was to integrate the Bonenburg section and its extremely well- preserved palynoflora within the existing framework of end-Triassic records, and describe and compare its paleoenvironmental changes and vegetation history during the end-Triassic mass extinction. In 2017 the outcrop of 'Bonenburg' in Western Germany came into the spotlight of paleontological studies after the discovery of a new species of reptile potentially representing the oldest fossil of plesiosaurian found worldwide to date. Unfortunately, the lack of age diagnostic macrofossils in the Triletes Beds complicate correlations of this end-Triassic record and the only available fossils for such purposes are organic walled microfossils, i.e. palynomorphs. A part of this thesis was thus to confirm the interpretation of a Rhaetian age (∼208-201 Ma) using paylnological data. Additionally, a stratigraphic framework was needed to correlate the locality of these new prominent reptile remains with other contemporaneous sections. The excellent preservation of palynomorphs in the new Bonenburg section provides informative insights for stratigraphic, taxonomic and paleoecological purposes. Amongst paleoecologists studying the end-Triassic biotic crisis, it is still disputed whether animals and plants were affected alike. It is also disputed whether plants show similarly raised values of extinction as animals do, and whether they indicate severe terrestrial changes that might also have affected marine life, fostering faunal extinction. To achieve the overarching aim, the thesis pursues three main objectives. (1) To confirm the Rhaetian age of the plesiosaur and to characterise and correlate the new section palynostratigraphically with other European sections. Special focus lies on the potential correlation of the similarly reddish Triletes Beds in the Germanic Basin and Schattwald Beds in the Eiberg Basin. (2) To provide an environmental reconstruction and record of the vegetation history to determine whether and how terrestrial systems were affected by a changing environment. To support palynological applications in the first two objectives as well as future studies, the thesis also attempts to (3) review and revise relevant palynotaxonomy and palynological practices. To meet the first objective, we used an interdisciplinary approach combining lithology, carbon isotope signatures, and macro- and microfossils of the Bonenburg section. Palynologically, we confirmed the Rhaetian age of the plesiosaur and a major result of our work was the integration of the qualitative palynostratigraphy. This enabled us to correlate this new locality with other contemporaneous European sections, and also supported correlation of the reddish Triletes Beds from the shallow epicontinental shelf of the Central European Basin, with the Schattwald Beds from the Eiberg Basin, i.e. the western Tethys shelf area. To address the second objective, we used a detailed quantitative palynological analysis. A palynofacies-zonation was established and compared with the respective palyno-assemblages. These showed similar patterns overall, however, minor differences indicated that palynological assemblages were not exclusively driven by facies change. A novel approach for a Triassic-Jurassic boundary section was applied investigating biodiversity patterns beyond taxonomic richness, which provided new insights into how severely the primary producers were affected by environmental changes. Two intervals of increased environmental stress were indicated, but these preceded the marine extinction. Preliminary results indicated an increased darkening of palynomorph walls at the transition from the Triletes to the Contorta beds, coinciding with the marine extinction event. However, further work is necessary to better understand the underlying causal mechanisms for the palynological 'dark zone' An important side observation of this study is the documentation of malformed pollen and spores, and tetrads, which opens an important new perspective for future study of this section. To approach the third objective, we consulted relevant type-material of Rhaetian key taxa of well-known German and Austrian palynologists (e.g., Potonié, Thiergarth, Schulz, Mädler, and Klaus). The challenges we encountered lead to the revision of existing palynotaxonomic practices as well as the proposal of new practices to aid future taxonomic works. These revised and new practices were then employed to revise several Rhaetian key taxa, which lead to the most extensive and up-to date catalogue of Rhaetian taxonomy of the Germanic Triassic. We also proposed emendation of the Code of Nomenclature for algae, fungi, and plants, to rectify a current problem that prevents designation of neotypes. The discussed palynotaxonomy in this thesis therefore not only revised Rhaetian paleopalynology in detail, but made a crucial contribution to paleobotany at large.
