Calcareous dinoflagellate cysts or calcareous dinocysts are dinoflagellate cysts produced by a group of peridinoid

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

s, called

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

Definition

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

dinoflagellates The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

, called

. Such calcareous structures are either

dinocysts Dinocysts or dinoflagellate cysts are typically 15 to 100 μm in diameter and produced by dinoflagellates as a dormant, zygotic stage of their lifecycle, which can accumulate in the sediments as microfossils. Organic-walled dinocysts are ofte ...

(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 unranked clade or superphylum within Eukaryota. They are currently grouped with the Stramenopiles and Rhizaria among the protists with tubulocristat ...

,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 ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

and are highly diverse during the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

and throughout the

Tertiary Tertiary (from Latin, meaning 'third' or 'of the third degree/order..') may refer to: * Tertiary period, an obsolete geologic period spanning from 66 to 2.6 million years ago * Tertiary (chemistry), a term describing bonding patterns in organic ch ...

.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