Dinoflagellates are biflagellate, eukaryotic protists that comprise a large proportion of planktonic biomass and are therefore important components of marine and freshwater environments. Most dinoflagellates are either photosynthetic or heterotrophic, but some can be both.
Some dinoflagellate species (~15-20% of modern species ) produce a resting cyst, capable of being preserved in the sedimentary record, during the sexual phase of their life cycle and in preparation for a dormant period. These cysts are found throughout the world in surface sediments  and cysts recognized as produced by dinoflagellates have been reliably identified as far back as the Triassic (~250 Ma).
Dinoflagellate cysts may be organic-, calcareous- or, rarely, siliceous-walled. Organic-walled dinoflagellate cysts are composed of a resistant biomacromolecule termed dinosporin, which is unique to dinoflagellates. The primary method for identifying cyst species is through their morphology , particularly an opening in the cyst wall through which the dinoflagellate cell emerges called an archeopyle. Dinoflagellate cysts are exceedingly useful (i)] as sensitive environmental indicators in modern freshwater [4,5] and marine settings [6-14], often in conjunction with pollen , and (ii) in deeper time studies and biostratigraphy [16-21]. They therefore constitute an important link between organisms, the environment in which the cells lived, and the geological record.
- Lentin and Williams Index of fossil dinoflagellates
- Click here for the accompanying DINOFLAJ3 database