Chrysanthemodiscus A.Mann, 1925

Holotype species: Chrysanthemodiscus floriatus A.Mann

Original publication and holotype designation: Mann, A. (1925). Marine diatoms of the Philippine Islands. Bulletin United States National Museum 100(6, part 1): 1-182, 39 pls.

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Description: An epiphytic, marine diatom with delicate cylindrical cells (often 4-6 times as long as wide) and convex valves, attached end-to-end by means of mucilage pads arising from the valve centres. Sometimes, however, cells are attached by pads near the valve margins and appear heterovalvate - one being domed and the other flatter and notched. Plastids numerous, discoid. Often abundant on macroscopic algae along tropical shores but only rarely reported, e.g. from Oahu, Hawaii (Round, 1978b), off Florida (Gibson & Navarro, 1981) and from the coast of Oman (samples from S. Hiscock). Valves domed with concentric undulations or rises (see Gibson & Navarro). Centrally with a cluster of 'pegged', round areolae (probably of the rota type) within the annulus, and outside this with radiating rows of areolae whose lengths change as they approach the centre. The vela are delicate and in most specimens only 'pegs' remain of what were possibly rotae located in somewhat radially elongate areolae. No distinct valve mantle. Internally no more detail is obvious. There are no portulae. Cingulum composed of numerous complete copulae of similar form, with vertical rows of areolae of similar structure to those of the valve. Proximal edges of bands slightly fimbriate.

The most recent alteration to this page was made on 2015-12-09 by M.D. Guiry.

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

Most recent taxonomic treatment adopted: Nikolaev, V.A., Kociolek, J.P., Fourtanier, E., Barron, J.A. & Harwood, D.M. (2001). Late Cretaceous diatoms (Bacillariophyceae) from the Marca Shale member of the Moreno Formation, California. Occasional Papers of the California Academy of Sciences 152: 1-119, 39 plates.

Comments: Round (1978b) suggested that this was a distinctive diatom which should be placed in its own family, the Chrysanthemodiscaceae. Simonsen (1979) removed it to the subfamily Stictodiscoideae of the Biddulphiaceae, a subfamily containing so many diverse diatoms in his treatment as to be unacceptable: we retain the original family. Whilst preparing this account we found that Takano (1965) had rediscovered C. floriatus in waters off Japan and his light micrographs are the best we have seen of this genus. He also points out that Melchersiela described by Teixeira (1958) is probably congenric.

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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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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 09 December 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 11 December 2023

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