Calcareous dinoflagellate cysts or calcareous dinocysts are

dinoflagellate cysts 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- ...

produced by a group of peridinoid dinoflagellates, called

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an ad ...

dinoflagellates.

Definition

Organisms producing calcareous structures are exclusively found in a small group of peridinoid

dinoflagellates The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates a ...

, called

. Such calcareous structures are either

dinocysts 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- ...

(systematized as CalciodinelloideaeFensome, R.A., Taylor, F.J.R., Norris, G., Sarjeant, W.A.S., Wharton, D.I., Williams, G.L., 1993. A classification of living and fossil dinoflagellates. Micropalaeontology (Special Publication) 7, 1–245.), which are formed during the life cycle (i.e., mostly hypnozygotes, after sexual reproduction, or resting stages; an overview of potential cyst formations is given by) or found in vegetative stages (namely in ''Thoracosphaera'' Kamptner). The potential to produce calcareous structures has been considered as apomorphic within

alveolates The alveolates (meaning "pitted like a honeycomb") are a group of protists, considered a major clade and superphylum within Eukarya. They are currently grouped with the stramenopiles and Rhizaria among the protists with tubulocristate mitochond ...

,Kohring, R., Gottschling, M., Keupp, H., 2005. Character traits and palecological significance of calcareous dinoflagellates—an overview. Paläont. Z. arguing for the monophyly of Calciodinellaceae (including ''Thoracosphaera''Janofske, D., 1992. Kalkiges Nannoplankton, insbesondere kalkige Dinoflagellaten-Zysten der alpinen Ober-Trias: Taxonomie, Biostratigraphie und Bedeutung für die Phylogenie der Peridiniales. Berliner Geowiss. Abh. (E) 4, 1–53.).

Distribution and ecology

Calciodinellaceae (Peridiniales, Dinophyceae) comprise 35 extant species of calcareous dinophytes, plus about 260 fossil species. They are distributed in cold through tropical seas of the world (neritic and pelagic). Calcareous cysts are deposited in both marine sediments that are coastal and oceanic. The first freshwater dinoflagellate that produces calcareous cysts was recently discovered.

Fossil record

According to the fossil record, calcareous

originate in the Upper

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

and are highly diverse during the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

and throughout the

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

.Keupp, H., 1991. Fossil calcareous dinoflagellate cysts. In: Riding, R. (Ed.), Calcareous Algae and Stromatolites. Springer, Berlin, pp. 267–286.

Systematics

Due to their long stratigraphic range, many fossil species (namely their cysts) have been described. By contrast, descriptions of extant species are primarily based on the motile stages (namely on the thecae, which are less diverse). This has led to two distinct systematics: paleontological (with four subordinate groups, primarily based on the cyst wall ultrastructure, of which the c-axes of the crystals are orientated irregularly oblique, regularly radial, regularly tangential, or regularly oblique) and neontological (with the motile taxa ''Bysmatrum'' Faust and Steidinger, ''Ensiculifera'' Balech, ''Pentapharsodinium'' Indelicato and Loeblich III, and ''Scrippsiella''Steidinger, K.A., Tangen, K., 1996. 3. Dinoflagellates. In: Tomas, C.R. (Ed.), Identifying Marine Diatoms and Dinoflagellates. Academic Press, San Diego (California), pp. 387–583.).

References

{{reflist Dinoflagellate biology