Helicosphaera


Classification: Coccolithophores -> Zygodiscales -> Helicosphaeraceae -> Helicosphaera
Sister taxa: Helicosphaera,

Distinguishing features: Coccoliths with helical flange; arranged spirally on the coccosphere


Daughter taxa: (blue => in age window 0-300Ma) Granddaughter taxa
Living and Neogene medium to large species (typically 7-11 microns) with flanges that end in distinct wings.

Miocene small to medium sized Helicosphaera species with wing ending flush with flange rather than terminating abruptly. Openings usually strongly oblique. Blanket confiend to central area, in xpl flange dark around whole coccolith.

Early Miocene group of large Helicosphaera species with weak wing, and blanket confined to central area

Late Oligocene to Mid Miocene species; flange terminates abruptly rather than expanding into a wing; blanket largely confined to central area, so flange is dark is dark in cross-polars; bar conjunct with rim, horizontal or inversely oriented.

Paleogene species; flange does not expand into a wing; bar conjunct or disjunct with rim, normally oriented.

Specimens which cannot be assigned to established species

Taxonomy:

Citation: Helicosphaera Kamptner, 1954
Rank: Genus
Type species: Helicosphaera carteri
Synonyms:

 

Notes & discussion: Drawings:  the drawings used in the table above are from Theodoridis (1984).
Subdivision
: The large number of described species have been variously subdivided into sub-groups by different workers (e.g. Theodoridis 1984, Aubry 1990, Young 1998). The subdivision followed here is based on Young (1998) which followed previous work. The main Paleogene and Neogene groups are respectively the lophota and carteri groups. The recta group is an additional well-separated Oligo-Miocene lineage. Finally the walbersdorfensis and ampliaperta groups include some distinctive Miocene species, although the separation from the carteri group is somewhat subjective.
Alternative taxonomy: Aubry & Bord (2009) proposed an alternative taxonomy for the species conventionally included in Helicosphaera on the basis that there is "morphostructural evidence" that  Helicosphaera carteri evolved from Pontosphaera in the Late Oligocene, rather than from other Helicosphaera species such as H. intermedia or H. euphratis. The nature of this morphostructural evidence is not explained, however the proposal seems extremly unlikely to us since Helicosphaera is a distinctive and unique set of species. In particular the spiral  coiling of the shield in Helicosphaera is a unique feature within the coccolithophores and is essentially identical in all species conventionally included in Helicosphaera.  Moreover intermediates occur between the species H. euphratis, H. intermedia and H. carteri, indeed in the Early Miocene it is often dificult to separate these species. Hence we regard it as highly unlikely that Helicosphaera is polyphyletic and this further means that the genera Helicosphaerella, and Helicosphaeroides,  are unnecessary. They could, of course, still be used - for respectively the H. recta group and the H. lophota group as recognised here. However, the proposed names are confusingly similar so using them does not seem advantageous.

Farinacci & Howe catalog pages: Helicopontosphaera * Helicosphaera + * Helicosphaerella * Helicosphaeroides *

Distinguishing features: Coccoliths with helical flange; arranged spirally on the coccosphere


Morphology remarks: Coccoliths with helical flange, formed of V-units.  surrounding a proximal plate of regular R-units. The R-units also extend to thedistal surrface but  show much les sregular shape and ar termed the "blanket". Theosdoridis 1984 gives a very detailed descrition and Young et al. (2004) a modern analysis uing observations from culture.  
Various sub-groups can be recognised based on presence/absence of a disjunct bar, bar orientation, degree to which the blanket (R-units) covrs the flange (V-units), termintion of the flange, etc. (see e.g. Theodoridis 1984, Perch-Nielsen 1985b, Aubry 1990, Young 1998).
There is however also signifiant variation within all species, notably in degree of development of the wing. In modern Helicosphaera carteri this can be seen to be relsted to position on the coccosphere, with the coccoliths around the flagellar opning typiclly having especially wel-devloped wings.

Search data:
TagsLITHS: placolith, asymmetric, RIM: wing,
CSPH: ellipsoidal, varimorphic, V-UNITS: distal shield, R-UNITS: blanket, c-str, px-plate, DETAILS: rim-bicyclic, isogyres kinked, isogyres oblique, isogyres separated,
MetricsLith size: 4->22µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): in lower part of Ypresian Stage (28% up, 53.7Ma, in Ypresian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Aubry, M.-P. & Bord, D., (2009). Reshuffling the cards in the photic zone at the Eocene/Oligocene boundary. In: Koeberl, C. and Montanari, A. (Editors), The Late Eocene Earth—Hothouse, Icehouse, and Impacts. Geological Society of America Special Paper. 452, pp. 279–301.

Aubry, M.-P., (1990). Handbook of Cenozoic calcareous nannoplankton. Book 4: Heliolithae (Helicoliths, Cribriliths, Lopadoliths and others). Micropaleontology Press, American Museum of Natural History, New York, 381 pp.

Jafar, S.A. & Martini, E., (1975). On the validity of the calcareous nannoplankton genus Helicosphaera. Senckenbergiana lethaea, 56: 381-397.

Kamptner, E., (1954). Untersuchungen über den Feinbau der Coccolithen. Anzeiger. Österreichische Akademie der Wissenschaften. Mathematische-Naturwissenschafliche Klasse. Wien, 87: 152-158.

Perch-Nielsen, K., (1985). Cenozoic calcareous nannofossils. In: Bolli, H.M., Saunders, J.B. and Perch-Nielsen, K. (Editors), Plankton Stratigraphy. Cambridge University Press, Cambridge, pp. 427-555.

Theodoridis, S., (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin, 32: 1-271.

Young, J.R., (1998). Neogene. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 225-265.

Young, J.R.; Henriksen, K. & Probert, I., (2004). Structure and morphogenesis of the coccoliths of the CODENET species. In: Thierstein, H.R. and Young, J.R. (Editors), Coccolithophores - From molecular processes to global impact. Springer, pp. 191-216.


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Helicosphaera compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 11-12-2018

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