“Bithynian and Pelsonian (Anisian, Middle Triassic) Ammonoidea are generally rare in the Germanic Basin. Here, we describe ammonoids from the Jena and Rüdersdorf formations (Lower Muschelkalk) of Rüdersdorf (Brandenburg, Germany). This locality is peculiar in its isolated situation and its comparatively high diversity in ammonoids. This outcrop yielded several assemblages encompassing eight species: Balatonites ottonis (Buch, 1849), B. balatonicus (Mojsisovics, 1873), B. egregius (Arthaber, 1896), Beneckeia buchi (Alberti, 1834), Bulogites zoldianus (Mojsisovics, 1882), “Ceratites” antecedens (Beyrich, 1858), Discoptychites dux (Giebel, 1853) and Noetlingites strombecki (Griepenkerl, 1860). When the geographic distribution of these species are compared, it becomes evident that immigrants from the southeast and the southwest met in that region. Such immigrations were only possible during transgressions. Balatonites balatonicus, B. egregius and B. zoldianus are recorded from the area for the first time. Beneckeia is revised with a focus on Ben. buchi, one of the few true endemites of the Germanic Basin, using synchrotron data to describe its early ontogeny. The holotype of “Ceratites” antecedens is figured for the first time and a lectotype for Balatonites egregius is designated” – read on ResearchGate