Cyclostephanos Round, 1987

Lectotype species: Cyclostephanos novae-zeelandiae (Cleve) Round

Original publication and holotype designation: Theriot, E., Håkansson, H., Kociolek, J.P., Round, F.E. & Stoermer, E.F. (1988 '1987'). Validation of the centric diatom genus name Cyclostephanos. British Phycological Journal 22(4): 345-347.

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Description: Cells short, disc-shaped, solitary or in short chains. Valves circular, with a concentric undulation and spines around the margin. Plastids discoid. Freshwater, planktonic. Previously included within Stephanodiscus. Valves with radiating lines of areolae, grouped into fascicles around the margin and separated by raised, rounded ridges. Areolae continuing down valve mantle in separate fascicles. Spines occur on ridges at the edge of the 'valve face' and the fultoportulae open below these, usually close to the valve edge, which may be well developed. No clear distinction between valve face and mantle. Central region of valve face variously nodulose or plain. Areolae simple, internally with domed cribra. Struts or ribs extend in from the valve edge onto the valve face internally between the fascicles of areolae but they do not form distinct chambers in species investigated to date. There is a ring of fultoportulae on the mantle, each opening internally onto one of the struts between the fascicles; scattered fultoportulae may also occur on the valve face: all these have only two satellite pores. A single rimoportula may be present. Copulae porous, split, with ligulae; areolae much finer than on the valve.

The most recent alteration to this page was made on 2021-10-03 by M.D. Guiry.

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

Gender: This genus name is currently treated as masculine.

Most recent taxonomic treatment adopted: Houk, V., Klee, R. & Tanaka, H. (2014). Atlas of freshwater centric diatoms with a brief key and descriptions. Part IV. Stephanodiscaceae B. Stephanodiscus, Cyclostephanos, Pliocaenicus, Hemistephanos, Stephanocostis, Mesodictyon & Spicaticribra. Fottea (Supplement) 14: 1-530.

Comments: This genus was erected by Round (1981d) to include Stephanodiscus dubius and S. novae-zeelandiae since these differed from other Stephanodiscus species in having the fascicles of areolae continued down the valve 'mantle' and internal ribbin in the 'mantle' region; the name was made valid in Theriot et al. (1987). Cyclostephanos differs from Cyclotella in the extension of the rows of fascicles to the centre of the valve and the presence of a single ring of spines around the valve face. The internal folds/struts are reminiscent of Cyclotella but are not developed to the same extent. They do, however, suggest a relaiotnship, hence the generic name. C. damasii (Hust.) Stoermer & Håkansson (1983) can be added to the list of species. Further discussion and figures of S. African forms can be found in Schoeman et al. (1984) and Theriot, Stoermer & Håkansson (1987) discuss in detail the rimoportulae in this genus and in Cyclotella.

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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. 03 October 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 02 October 2022

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