Dinocysts are produced by around 10% of living Dinoflagellates as a dormant zygotic stage of their lifecycle. The next-generation Dinoflagellate exits the cyst (excysts) via the archaeopyle, a hole which may take the form of the removal of the apex of the cyst (apical archaeopyle), or the removal of one of the tabulæ (Precingular archæpyle).

Dinocysts are composed of Dinosporin, an organic compound similar to sporopollenin

Sporopollenin

thumb|right|270px|[[Scanning electron microscope|SEM]] image of pollen grainsSporopollenin is a major component of the tough outer walls of spores and pollen grains. It is chemically very stable and is usually well preserved in soils and sediments...

, but unique to Dinoflagellates.

The tabulation of the Dinoflagellate is mirrored in the 'paratabulation' of the Dinocyst, allowing species to be deduced from the cyst (Fensome and Taylor, 1933).

Dinocysts are essentially the only evidence in the fossil record of Dinoflagellates; nonetheless they have been discovered as early as the Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

.