Holotype species: Amphitetras antediluviana Ehrenberg
Original publication:Ehrenberg, C.G. (1840). Über noch zahlreich jetzt lebende Thierarten der Kreidebildung und den Organismus der Polythalamien Preprint of Abhandlung der Könglichen Akademie der Wissenschaften zu Berlin aus dem Jahre 1839  with different pagination. pp. 1-94, 4 pls. Berlin.
Type designated in 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.
Taxonomic status: currently recognized as a distinct genus.
Most recent taxonomic treatment adopted: Sims, P.A., Williams, D.M. & Ashworth, M.[P.] (2018). Examination of type specimens for the genera Odontella and Zygoceros (Bacillariophyceae) with evidence for the new family Odontellaceae and a description of three new genera. Phytotaxa 382(1): 1-56, 156 figs, 2 text-figs.
Description: Cells forming zig-zag colonies attached to seaweeds, often with conspicuous mucilage pads between cells; these pads appear 'collar-like' in some of our material. Plastids numerous, plate-like. Not uncommon and probably of world-wide distribution. Valves quadrate, often with concave sides. Superimposed upon the quadrate morphology there is a central circular dome with a depressed centre. Prominent ocelli occur on low elevations at the angles. Valve framework massive, sometimes granulose or spinulose, and sometimes with branching spinules near the mantle edge. Areolae occluded by cribra located near the outside surface, some of which bear fine spinules. The edge of the valve mantle is formed into internal and external flanges; the latter is turned upwards parallel to the valve mantle and is often quite deep and in some valves finely granular. Internally the underlying centric radiating system of costae is obvious at the centre of the valve; here there are a few simple pores through the framework. Rimoportulae absent. Copulae are complete, areolate with cribra of the same form as those of the valve but lying flush with the siliceous framework which is more laminate than that of the valve. The valvocopula has an inwardly directed pars interior, which underlaps the valve.The most recent alteration to this page was made on 10 Jan 2019 by M.D. Guiry.
Comments: The siliceous framework of the valve is very similar to that of Isthmia. The genus Amphitetras has formerly been placed in Biddulphia, Triceratium and Stictodiscus. With the redefinition of these genera, Amphitetras remains as a distict entity. An extremely detailed and fascinating account of A. antediluvianum is given by Liebisch (1928) in which he also figures auxospore formation involving expansion of the cytoplasm in the distal region of the hypocingulum which then splits as further expansion of the auxospore wall occurs. The primary cell is formed within the auxospore while still attached to the hypovalve, as in Melosira varians. The classification of genera in the order Biddulphiales is still in a state of flux. Amphipentas is possibly to be included within Amphitetras but a position in Stictodiscus also needs consideration.
Numbers of names and species: There are 59 species names in the database at present, as well as 1 infraspecific names. Of the species names, 4 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.
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: 23 April 2002 by M.D. Guiry
Verified by: 10 January 2019 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=44350
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 22 October 2021.