Dinoflagellate cysts and associated aquatic palynomorphs from the Tendaguru Beds (Upper Jurassic‐Lower Cretaceous) of Southeast Tanzania

Abstract

Dinoflagellate cysts and associated aquatic palynomorphs have been recovered from the dinosaur‐bearing Tendaguru Beds (Upper Jurassic‐Lower Cretaceous) at Tendaguru, a hill in southeast Tanzania. Palynofloras from these beds are generally dominated by pollen grains of Mesozoic conifers (mainly Classopollis), but dinoflagellate cysts occur sporadically throughout the succession. They attain highest relative abundances and diversities in the marine intercalations between the Saurian Beds, namely in the Nerinea Bed (between the Lower and Middle Saurian Beds) and even more so in the Trigonia smeei Bed (between the Middle and Upper Saurian Beds). Peak levels of dinoflagellate cysts correspond to times when the shallow marine environments of the Nerinea and Trigonia smeei Beds had access to the open sea, while scarcity or absence of dinoflagellate cysts in the Saurian Beds is related to intervals of restricted access to the sea in tidal flat and coastal plain environments. Four informal dinoflagellate cyst assemblages can be distinguished in the Tendaguru Beds: 1. the Rigaudella aemula‐Chlamydophorella wallala assemblage from the Nerinea Bed (Oxfordian to Kimmeridgian); 2. the Endoscrinium attadalense‐Ctenidodinium sellwoodii group assemblage from the Middle Saurian Bed (late Kimmeridgian); 3. the Dingodinium jurassicum‐Kilwacysta assemblage from the Trigonia smeei Bed (Tithonian); 4. the Muderongia‐Oligosphaeridium assemblage probably from the Trigonia schwarzi Bed at Namunda Plateau, 8 km south of Tendaguru (late Valanginian to Hauterivian). The age determinations are based on correlation with known dinoflagellate cyst ranges and zonations in Australia, Europe and elsewhere. However, the stratigraphic position and previous biostratigraphic interpretations of the Tendaguru Beds based on ammonites, charophytes and ostracods were also taken into consideration. One new genus (Kilwacysta), three new species (Kilwacysta multiramosa, Kilwacysta semiseptata and Protobatioladinium lindiensis) and the new combination Barbatacysta capitata are proposed.