Porosira Jørgensen, 1905
Holotype species: Porosira glacialis (Grunow) Jørgensen
Original publication and holotype designation: Jørgensen, E.G. (1905). Diatoms in bottom samples from Lofoten and Vesteraalen. In: Hydrographical and Biological Investigations in Norwegian Fiords. (Nordgaard, O. Eds), pp. 95-225. Bergen: Bergens Museum Skrift, John Grieg.
Description: Cells short, cylindrical, attached by mucilage to form filaments of spaced cells. Numerous fine polysaccharide threads also radiate from the valves. Plastids disc-like. Marine, planktonic. Valves watchglass-like with a central annulus and radiating rows of areolae; no real mantle. Areolae loculate, opening to the exterior by elongate foramina. Internally the areolae are closed by finely perforate cribra. Fultoportulae are scattered over the whole of the valve but become more frequent around the margin; they have simple openings or short stalks externally and are unremarkable internally, resembling those of Thalassiosira. A single flattened rimoportula, with a short stalk is located to the inside of the denser region of fultoportulae; the external opening is on a slight elevation. Copulae numerous, split, with areolae similar to those of the valve.The most recent alteration to this page was made on 2019-10-20 by Salvador Valenzuela Miranda.
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: This genus is close to Thalassiosira and Lauderia but Hasle (1973a) considered it sufficiently distinct to maintain as a separate genus. In Lauderia, cell-to-cell contact is maintained via prolongations of the processes, while in Thalassiosira it is via the central group of fultoportulae.
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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in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.
Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=44442
Cite this record as:
Salvador Valenzuela Miranda in Guiry, M.D. & Guiry, G.M. 20 October 2019. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 27 March 2023