A gymnosperm pollen not a dinoflagellate: a new combination for Mendicodinium? quadratum and description of a new pollen species from the Jurassic of Tanzania

Abstract

A palynological investigation of outcrop samples from the Upper Jurassic part of the dinosaur-bearing Tendaguru Beds, southeast Tanzania, yielded well-preserved material of the alleged dinoflagellate Mendicodinium? quadratum. Combined scanning electron microscopy (SEM) and light microscopy showed that this species does not possess an epicystal archeopyle encircling the grain as would be expected in the dinoflagellate genus Mendicodinium. Rather, its opening is a sulcus confined to one side of the grain, commonly expanded at one or both ends. Therefore, M.? quadratum is interpreted here as a monosulcate gymnosperm pollen, and transferred to the genus Shanbeipollenites, which was originally described from the Jurassic of China. In the Tendaguru Beds Shanbeipollenites quadratus is associated with the new species Shanbeipollenites proxireticulatus. Both species occur in marine and possibly nonmarine parts of the section. This distribution pattern and some morphological peculiarities of the latter species (proximal reticulum, rare dyads) support the interpretation of both species as gymnosperm pollen.