Hemiaulus Ehrenberg, 1844, nom. rejic.

Holotype species: Hemiaulus antarctica Ehrenberg

Currently accepted name for the type species: Eucampia antarctica var. recta (Mangin) G.Fryxell & A.K.S.K.Prasad

Original publication and holotype designation: Ehrenberg, C.G. (1844). Einige vorläufige Resultate seiner Untersuchungen der ihm von der Südpolreise des Captain Ross, so wie von den Herren Schayer und Darwin zugekommenen Materialien über das Verhalten des kleinsten Lebens in den Oceanen und den grössten bisher zugänglichen Tiefen des Weltmeeres. Bericht über die zur Bekanntmachung Geeigneten Verhandlungen Der Königl. Preuss. Akademie Der Wissenschaften zu Berlin 1844: 182-207.

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Description: Cells united by short or long processes to form straight or curved chains. Plastids small, discoid. A common marine planktonic genus with many fossil representatives (up to 90 spp. according to VanLandingham, 1971) but many require re-investigation (see Ross & Sims, 1985, for the removal of some to Briggera - also p. 272). Valves elliptical with long thin processes linking by apical spines (the species originally in Hemiaulus but having bulbous endings to the processes no longer belong here). Valve face curved, merging imperceptibly with the deep mantles. Areolae: simple round pores (H. hauckii) or large elliptical to rectangular holes closed by complex cribra (H. sinensis: figs 20-33 of Ross, Sims & Hasle, 197?). One rimoportula usually present in a central or offset position (cf. Eucampia) but sometimes absent. Copulae more finely areolate than the valves, split with pointed ends.

The most recent alteration to this page was made on 2011-10-20 by M.D. Guiry.

Taxonomic status: This name is currently regarded as a synonym of Eucampia.

Comments: At the LM level Hemiaulus is not usually confused with Eucampia but in the elctron microscope there are similarities (see also Syvertsen & Hasle, 1983). The absence of pseudocelli of the Eucampia type we regard as sufficient to maintain the genera separate. The three general Hemiaulus, Eucampia and Climacodium form a distinct group of genera with two elongated processes on each valve, both processes linking to form chains. However, Eucampia has distinct features (e.g. the costate ocellus) allying it to Cerataulina. Recently Ross & Sims (1985) have erected the genus Briggera to encompass a number of fossil species which have swollen ends to the processes and interlocking spines (see p. 272). Sims (1986), in describing two genera from the Eocene not illustrated here, Ailuretta Sims and Sphynctolethus Hanna, provides a link with present-day members of the subfamily Hemiauloideae, namely Cerataulina, Eucampia and Hemiaulus. There is little doubt that selection since the Cretaceous has eliminated many species of Hemiaulus, leaving only the lightly silicified, rather delicate forms.

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Contributors
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=47523

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 20 October 2011. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 19 April 2024