163,770 species and infraspecific names are in the database, 22,783 images, 63,043 bibliographic items, 481,350 distributional records.

Thalassiosira Cleve, 1873

Empire Eukaryota
Kingdom Chromista
Phylum Bacillariophyta
Subphylum Bacillariophytina
Class Mediophyceae
Subclass Thalassiosirophycidae
Order Thalassiosirales
Family Thalassiosiraceae

Holotype species: Thalassiosira nordenskioeldii Cleve

Original publication and holotype designation: Cleve, P.T. (1873). On diatoms from the Arctic Sea. Bihang till Kongliga Svenska Vetenskaps-Akademiens Handlingar 1(13): 1-28, 4 pl.
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Taxonomic status: currently recognized as a distinct genus.

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Stoermer, E.F. & Julius, M.L. (2003). Centric Diatoms. In: Freshwater Algae of North America. (Wehr, J.D. & Sheath, R.G. Eds), pp. 559-594. San Diego: Academic Press.

Taxonomic notes
Coscinodiscophyceae (Marie et al., 2017: table 4). - (24 May 2017) - Wendy Guiry

Description: Cells discoid to cylindrical, solitary, or joined by threads or valve to valve to form loose chains; or in mucilage masses. Plastids numerous, discoid. Mainly in the marine plankton. Valve circular, with a flat valve face and short downturned mantles or sometimes almost watchglass-like. Areolae usually loculate, arranged in radial rows, tangential rows, or arcs; varying in size and prominence. The areolae open to the outside by circular foramina, sometimes with finger-like projections (e.g. T. ferrelineata); internally they are occluded by slightly raised cribra. Valve mantle edge often very prominently ribbed and rimmed. Fultoportulae are present in a ring around the valve mantle opening externally by short tubes; in some species scattered or grouped fultoportulae occur also on the valve face. The internal fultoportula structure varies; very short to very long tubes are surrounded by (3 or) 4 buttresses. Each valve usually has one rimoportula, which opens externally through a larger and more obvious tube, located somewhat internal to the marginal ring of fultoportulae; in some cases, however, the external tube can be thin and located close to fultoportulae (e.g. T. conferta); in a few species a rimoportula may occur in the centre of the valve face. The internal rimoportula opening is usually elongate and sessile. The mangle edge may be thickened internally in some species. Copulae numerous, split and ligulate. The valvocopula is more obviously areolate than the other copulae, with a loculation similar to that of the valve and a more conspicuous row of areolae adjacent to the valve mantle. A slight septum occurs on the valvocopula of T. trifulta which also has a complex triradiate ligula

The most recent alteration to this page was made on 12 Aug 2021 by M.D. Guiry.

Comments: This is a large genus - descriptions of species (many new) are to be found in the numerous papers of Hasle & Fryxell. Most species (c. 100) are marine, although up to 12 have been recorded in freshwaters (Hasle, 1978); of the latter T. weissflogii (=T. fluviatilis) is probably the best known. There is considerable variation within the genus, which is one of the largest in our collection; we cannot do justice to it in our illustrations. Makarova (1988) provides a comprehensive account of the genus in seas around Russia.

Numbers of names and species: There are 287 species names in the database at present, as well as 42 infraspecific names. Of the species names, 175 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..

Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):

Click here to also show infraspecific names in the list below.

Hustedt, F. (1930). Bacillariophyta (Diatomeae) Zweite Auflage. In: Die Süsswasser-Flora Mitteleuropas. Heft 10. (Pascher, A. Eds), pp. [i]-vii, [1]-466. Jena: Verlag von Gustav Fischer.

Tomas, C.R., Eds (1996). Identifying marine diatoms and dinoflagellates. pp. 1-858. San Diego: Academic Press Inc.

Round, F.E., Crawford, R.M. & Mann, D.G. (1990). The diatoms biology and morphology of the genera. pp. [i-ix], 1-747. Cambridge: Cambridge University Press.

Johansen, J.R. & Fryxell, G.A. (1985). The genus Thalassiosira (Bacillariophyceae): studies on species occurring south of the Antarctic Convergence Zone. Phycologia 24(2): 155-179, 81 figs, 2 tables.

Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.

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.

Created: 11 April 2002 by M.D. Guiry

Verified by: 12 August 2021 by M.D. Guiry

Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=43768

Citing AlgaeBase
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 16 October 2021.

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