Stephanopyxis (Ehrenberg) Ehrenberg, 1845

Holotype species: Pyxidicula aculeata Ehrenberg

Currently accepted name for the type species: Stephanopyxis aculeata (Ehrenberg) Ehrenberg

Original publication and holotype designation: Ehrenberg, C.G. (1845). Neue Untersuchungen über das kleinste Leben als geologisches Moment.. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin, 1845: 53-87.

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Description: Cells cylindrical to almost spherical, joined by processes into long filaments. Plastids discoid, lobed. A fairly common marine planktonic genus tending to be tropical in distribution but carried into colder waters by currents. Also common in fossil deposits where it exhibits a larger number of species - some may be resting spores. Valves domed, hemispherical to discoid; without obvious distinction into valve face and mantle. Areolae large, hexagonal, opening outwardly by large foramina in shallow chamber; forming a base to the areolae is a layer of silica with a continuous series of poroids containing rotae, arranged in rows radiating from the valve centre. Areolae more regularly arranged towards the valve centre. A ring of tubular (sometimes half-tubular) processes is present; in some fossil forms additional processes occur in the centre. The processes arise as extensions of the walls of the areolae and articulate with those of the sibling valve. Low-lying rimoportulae occur in a ring beneath the processes, into which they open. A further ring of rimoportulae occurs around the valve margin, in the marginal row of loculate areolae, and these open to the outside by simple slits. The cingulum is composed of a complete (?) narrow valvocopula and numerous segmented bands. All have simple pores.

The most recent alteration to this page was made on 2023-01-06 by Salvador Valenzuela Miranda.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

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

Comments: It is reported (e.g. Hendey, 1964) that strands of cytoplasm pass up the processes and thus connect cell to cell; this requires confirmation and if this is so it is the only diatom we know which has such interconnections. Stephanopyxis does not fit easily into any higher grouping of genera, though Simonsen (1979) placed it in the Melosiraceae. Recently Nikolaev (1984) has erected a new family Stephanopyxaceae and this appears to be a more logical step but must be emended to Stephanopyxidaceae (see Silva, 1980). Further EM detail is provided by Round (1973).

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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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Salvador Valenzuela Miranda in Guiry, M.D. & Guiry, G.M. 06 January 2023. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 14 July 2024

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