Palynodinium is an extinct genus of organic-walled dinoflagellate cyst. It is a fossil species of dinoflagellate cyst used to demarcate the K/Pg boundary, which marks the terminal Cretaceous and the extinction of the dinosaurs. Palynodinium grallator was among the microfossils which lead to the recent discovery of the K/Pg event record in marine sediments of the northeast Pacific.