Dinocysts or
dinoflagellate cysts are typically 15 to 100 µm in diameter and produced by around 15-20% of living
dinoflagellates as a dormant, zygotic stage of their lifecycle, which can accumulate in the sediments as microfossils.
Organic-walled dinocysts are often resistant and made out of
dinosporin. There are also
calcareous dinoflagellate cysts and
siliceous dinoflagellate cysts. Many books provide overviews on dinocysts.