Trigonium Cleve, 1867

Holotype species: Trigonium arcticum (Brightwell) Cleve

Original publication and holotype designation: Cleve, P.T. (1867). Diatomaceer från Spetsbergen. Öfversigt af Kongl. Vetenskaps-Akademiens Förhandlingar, Stockholm 24(10): 661-670.

Description: Cells tri- to multiangular, rectangular in girdle view. Plastids discoid. A marine genus growing in zig-zag chains attached to seaweeds; cosmopolitan but most widely distributed in warm waters. Also fossil, from the Late Eocene to the present. Valves triangular to multiangular, elevated at the corners; with deep, vertical mantles. Surface apparently smooth but at high magnification small granules can often be seen. areolae more-or-less simple, arranged in rows radiating from the centre, becoming smaller at the angles to form pseudocelli; closed externally by a layer of silica in which there is a ring of usually six pores, each closed by rotae. A septum occurs at each corner. Our figure suggests that there is a septum on the valvocopula. Rimoportulae low lying, clustered in the centre of the valve; their external openings are inconspicuous. Cingulum deep, containing porous, complete copulae.

The most recent alteration to this page was made on 2015-12-07 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: Hendey (1964) clarified Cleve's description and rejected later modifications. His concept of the genus seems now to be accepted (e.g. by Glezer, 1975 and Hoban, 1983) although Simonsen (1974) has a different concept, using the name for Triceratium alternans. Keeping to the Cleve-Hendey concept helps to bring some order to the confusion of tri- and multiangular taxa. Hoban (1983) discusses and figures the type species of Trigonium; our material of another species (T. formosum?) is clearly in the same genus.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in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. 07 December 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 30 September 2022

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