Streptotheca Shrubsole, 1890, nom. illeg.

Holotype species: Streptotheca tamesis Shrubsole

Currently accepted name for the type species: Helicotheca tamesis (Shrubsole) M.Ricard

Original publication and holotype designation: Shrubsole, W.H. (1890). On a new diatom in the estuary of the Thames. Journal of the Quekett Microscopical Club, series 2 4: 259-262.

Description: Cells joined to form long, ribbon-like filaments, which are often twisted; in these there are no intervening apertures between the cells, which are square in girdle view. Plastids numerous, discoid, often located in cytoplasmic strands radiating from the central nucleus. A marine planktonic genus. Valves linear to elliptical, rounded at the apices and sometimes slightly swollen in the centre. Valve face flat; mantle very shallow, slightly more pronounced at the apices where it bears slit-like openings. The valve is unusual in that it consists of a simple flat lamina, which is porous but without any ribbing, except for slight vein-like thickenings at isolated points on the valve face and along the valve mantle (see also von Stosch, 1977). The slight thickenings on the valve surface are sometimes associated with slightly more pronounced pores than those scattered over the remainder of the valve. The areolae are apparently without vela. There is a central rimoportula with a short external tube (see also Hasle, 1975). The cingulum consists of numerous simple porous bands, which both Hasle and von Stosch thought might be half-bands; we still cannot resolve this point. In this diatom the greater part of the cell covering is composed of copulae.

The most recent alteration to this page was made on 2022-05-16 by M.D. Guiry.

Taxonomic status: This name is currently regarded as a synonym of Helicotheca.

Gender: This genus name is currently treated as feminine.

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: The taxonomic position of this diatom has been discussed by both Hasle (1975) and von Stosch (1977), possible places for it being near the Chaetoceraceae or Thizosoleniaceae, or in the cluster containing Lithodesmium, Bellerochea and Ditylum. Von Stosch clearly preferred a position in the latter cluster, associating it particularly with Neostreptotheca and Bellerochea. The valve structure of Bellerochea is not at all like that of Streptotheca but for the moment we see no better alternative.

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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. 16 May 2022. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 13 August 2022

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