Strangulonema Greville, 1865
Holotype species: Strangulonema barbadense Greville
Original publication and holotype designation: Greville, R.K. (1865). Descriptions of new and rare diatoms. Series XVI . Transactions of the Microscopical Society, New Series, London 13: 43-57 [last page as "75"], 2 pls [pls V, VI].
Request PDFFossil: 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 cylindrical, forming chains linked by spines arising from a valve face 'collar'. A fossil genus found in sediments of Eocene to Oligocene age. Valves circular, with deep mantles and a smooth raised 'collar' on the valve face, from which flattened furcate spines arise. The collar turns outwards around its apex and, besides spines, also bears downwardly directed projections, which may originally have linked with the remnants of upwardly directed projections visible on the valve mantle, to form a network over the depression formed around the collar. The interlocking spines are non-separable and in the second form illustrated seem to be completely fused between sibling cells. Areolae large, round or elliptical. The valve face areolae radiate from the centre and are slightly smaller than those of the mantle (P.A. Sims, personal communication); on the valve mantle the areolae are in vertical rows and in addition there are small pores through the framework. No vela have been detected in our material, which is eroded. We cannot comment on the occurrence of portulae. Copulae wide, complete, with widely spaced areolae.
The most recent alteration to this page was made on 2023-10-16 by M.D. Guiry.Taxonomic status: This name is of an entity that is currently accepted taxonomically.
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.
Comments: Round, Crawford & Mann (1990: 126) include a note which states: "We are not able to place this [genus] with any confidence - it resembles Aulacoseira but may eventually require its own family". According to VanLandingham (1978) this is a monotypic genus but our material suggests that this is not so. Without further information, especially on presence or absence of portulae, it is difficult to place this genus in a family. However, the indented 'collar' may represent a 'pseudosulcus' such as found in Autocoseira granulata and its relatives, and this might indicate a relationship.
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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=46617
Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 16 October 2023. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 26 April 2024
