Coscinodiscus Ehrenberg, 1839, nom. et typ. cons.

Lectotype species: Coscinodiscus argus Ehrenberg

Original publication and holotype designation: Ehrenberg, C.G. (1839). Über die Bildung der Kreidefelsen und des Kreidemergels durch unsichtbare Organismen. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1838: 59-147, pls I-IV, tables 1, 2.

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Fossil: This is a genus of fossil species, or a genus with a fossil type species, or a genus the type species of which was originally described as a fossil.

Description: Cells discoid, sometimes thin (like a coin) or more barrel-shaped, occasionally with valve mantle deeper on one side. Plastids numerous, discoid. Free-living, marine and often abundant in the phytoplankton. A few species reported from lakes but usually only in high conductivity waters and many records need checking. Widely distributed in the fossil record. Valves saucer-to petri-dish shaped. Valve face flat, sometimes depressed centrally; areolae radiating from central annulus, sometimes sectored. Ovoid and triangular forms occur as fossils. Valves loculate with complex external vela with central small pores and an external ring of larger openings. Vela often becoming diamond-shaped on valve mantle. The internal openings are foramina, often rimmed and becoming smaller on the valve mantle. Rimoportulae present at intervals around the valve; external openings simple; internally with small cup-shaped expansions. Macro-rimoportulae sometimes occur at intervals in the ring; these aree larger, sometimes with flat apical expansions and curled; the macro-rimoportulae open via larger external apertures. Copulae poroidal, split and ligulate.

The most recent alteration to this page was made on 2015-10-19 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Tomas, C.R., Eds (1996). Identifying marine diatoms and dinoflagellates. pp. 1-858. San Diego: Academic Press Inc.

Comments: This genus is also classified occasionally as being a member of the Bacillariophyta, Bacillariophyceae. See ING entry. This is a large genus and requires extensive study since there is much variation at the ultrastructural level. Fryxell (1978) has documented the typification. Several species have been removed to Thalassiosira, others to Actinocyclus - many of the changes involve species living in tropical lakes. C. nitidus has been transferred to Psammodiscus by Round & Mann (1980). Many small centric forms need checking and the position of the vela determined; any forms found to have fultoportulae are almost certainly Thalassiosira species. Sims (1989) has reviewed three subgroups of Coscinodiscus and discussed their stratigraphical distribution and phylogeny.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

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Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 19 October 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 13 April 2024

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