Palynodinium
Palynodinium is an extinct genus of organic-walled dinoflagellate cyst (or dinocyst). 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. Dinoflagellate cysts are estimated to be produced by 10–16% of living dinoflagellates as a dormant, zygotic stage of their life cycle, which can accumulate in marine sediments as microfossils. Organic-walled dinoflagellate cysts are noted for their resistance to degradation owing to their composition of dinosporin, a biopolymer similar to sporopolinin characteristic of many terrestrial palynomorphs. Their abundance, cosmopolitan distribution, and quality of preservation in the fossil record since the Middle Triassic make dinoflagellate cysts excellent indicators of primary productivity as well as tools for biostratigraphy and paleoenvironmental reconstructions. The scope of dinoflagellate cyst applications has resulted in ongoing collaborative efforts between industry and academia to refine their taxonomic classification and enhance their utility through database organization. References 

Dinoflagellates
Dinoflagellate biology
Endosymbiotic events
Cretaceous–Paleogene boundary
Cretaceous geology
Events that forced the climate
Extinction events
Paleogene geology

Palynology