Aulacodiscus, 1844, nom. cons.
Holotype species: Aulacodiscus crux Ehrenberg
Original publication and holotype designation: Ehrenberg, C.G. (1844). Mittheilung über 2 neue Lager von Gebirgsmassen aus Infusorien als Meeres-Absatz in Nord-Amerika und eine Vergleichung derselben mit den organischen Kreide-Gebilden in Europa und Afrik. Bericht über die zur Bekanntmachung Geeigneten Verhandlungen der Königl. Preuss. Akademie Der Wissenschaften zu Berlin 1844: 57-97.
Taxonomic status: currently recognized as a distinct genus.
Most recent taxonomic treatment adopted: 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.
This is a genus of fossil species, or a genus with a fossil type species, or a genus the type species of which was originally described as a fossil.
Description: Cells solitary, circular in valve view with conspicuous marginal processes. Truncated oblong in girdle view with the marginal processes protruding. Plastids not observed. A marine genus living associated with inshore sediments and sometimes attached to sand grains. Can form massive growths in the surf zone, e.g. along Copalis Beach, Oregon coast during certain years in the 1920s and 1930s (Lewin, 1974) and along California beaches recently (Holmes & Mahood, 1980). A very large, mainly fossil genus going back to the Cretaceous and exhibiting considerable diversity of valve and rimoportula form. Valve with a conspicuous hyaline area at the centre from which rows of loculate areolae radiate. The valve surface is often corrugated and the valve mantle is not differentiated from the rest of the valve. The areolae are closed by cribra externally and open internally by large foramina; we have some evidence that there is an internal occlusion of some kind in some species. Rimoportulae marginal, complex, opening externally either via a tube or onto a cap extending towards the valve centre. In capped forms, the processes often have 'fork-like' slits. The rimoportula is unique. The tube passes through the valve and ends internally in a curved slit, almost flush with the internal layer of the wall. This slit is either E-shaped or C-shaped and may be orientated with the opening of the E or C pointing to the centre or tangentially. Sometimes clear hyaline rays extend from the centre to the rimoportulae, these being best seen on the inside of valves. Copulae numerous, split, ligulate and antiligulate, fimbriate (at least on the valvocopula), with vertical rows of small areolae.The most recent alteration to this page was made on 27 Jan 2017 by M.D. Guiry.
Comments: Reviewed by Rattray (1888a) and Ross & Sims (1970) and studied intensively by Burke & Woodward (1963-74). The structure of A. amherstia is discussed by Venkateswarlu & Round (1973) and by Sims & Holmes (1983) (who regard it as A. johnsonii var. amherstia) and A. Kittonii by Holmes & Mahood (1980). Both Holmes & Mahood and Ross & Sims (1970) consider that the morphology of the rimoportula is a useful specific taxonomic character.
Numbers of names and species: There are 220 species names in the database at present, as well as 37 infraspecific names. Of the species names, 91 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: 27 January 2017 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=44356
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 26 September 2021.