Helicosphaera lophota


Classification: ntax_cenozoic -> Zygodiscales -> Helicosphaeraceae -> Helicosphaera -> H. lophota group -> Helicosphaera lophota
Sister taxa: H. clarissima, H. compacta, H. disrupta, H. reticulata, H. robinsoniae ⟩⟨ H. bramlettei, H. lophota, H. papillata, H. prolixa, H. seminulum, H. wilcoxonii

Taxonomy:

Citation: Helicosphaera lophota (Bramlette & Sullivan, 1961) Locker, 1973
Rank: Species
Basionym: Helicosphaera seminulum lophota Bramlette & Sullivan, 1961
Variants:

Distinguishing features: Elliptical, oblong or reniform Helicosphaera with wide flange and central area spanned by a broad, near-longitudinal disjunct bar usually with distinct median suture.

Farinacci & Howe catalog pages: H. seminulum lophota * , H. neolophota *


Morphology: The median suture in the bar may be obscure in poorly preserved speciemens - (written comment from Rui de Gama, 2017).

Search data:
TagsLITHS: placolith, asymmetric, CA: ca_disjunct, bar,
CSPH: elongated, monomorphic, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent,
MetricsLith size: 10->15µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within NP18 zone (36.97-37.32Ma, top in Priabonian stage). Data source: Theodoridis (1984) Perch-Nielsen (1985)
First occurrence (base): within NP12 zone (50.50-53.70Ma, base in Ypresian stage). Data source: Theodoridis (1984) Perch-Nielsen (1985)

Plot of occurrence data:

References:

Barron, J. A., Bukry, D. & Poore, R. Z. (1984). Correlation of the middle Eocene Kellogg Shale of Nothern California. Micropaleontology. 30(2): 138-170. gs

Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs V O

Bown, P. R. & Newsam, C. (2017). Calcareous nannofossils from the Eocene North Atlantic Ocean (IODP Expedition 342 Sites U1403–1411). Journal of Nannoplankton Research. 37(1): 25-60. gs V O

Bown, P. R. (2005d). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research. 27(1): 21-95. gs V O

Bramlette, M. N. & Sullivan, F. R. (1961). Coccolithophorids and related nannoplankton of the Early Tertiary in California. Micropaleontology. 7(2): 129-188. gs

Haq, B. U. (1973). Evolutionary trends in the Cenozoic coccolithophore genus Helicopontosphaera. Micropaleontology. 19(1): 32-52. gs

Jones, A. P. & Dunkley Jones, T. (2020). Middle Eocene to Early Oligocene calcareous nannofossils from the Nanggulan Formation, Java, Indonesia. Journal of Nannoplankton Research. 30(1): 57-79. gs V O

Locker, S. (1973). Coccolithineen aus dem Paläogen Mitteleuropas. Paläobotanik. 3: 735-836. gs

Perch-Nielsen, K. (1971c). Elektronenmikroskopische untersuchungen an Coccolithen und verwandten Formen aus dem Eozan von Danemark. Biologiske Skrifter, Kongelige Danske Videnskabernes Selskab. 18(3): 1-76. gs

Perch-Nielsen, K. (1977a). Albian to Pleistocene calcareous nannofossils from the Western South Atlantic, DSDP Leg 39. Initial Reports of the Deep Sea Drilling Project. 39: 699-823. gs V O

Perch-Nielsen, K. (1985a). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 427-555. gs

Self-Trail, J. (2011). Paleogene Calcareous Nannofossils of the South Dover Bridge core, Southern Maryland (USA). Journal of Nannoplankton Research. 32(1): 1-28. gs V O

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

Varol, O. (1998). Palaeogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 200-224. gs


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Helicosphaera lophota compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-1-2021

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=670 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (2)

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Rui da Gama

On the short diagnosis you have indicated "...near-longitudinal disjunct bar with distinct median suture". I would rephrase this as I have very good images of H. lophota without the distinct median suture. Please note, in some samples depending on preservation this feature appears faded or absent. My point becomes clear if you examine the images of H. lophota you are displaying herein...

I would suggest adding to the description "near-longitudinal disjunct bar with, in optimum preservation, a distinct median suture. As is, it might become confusing and make many of us use the cf. pre-fix unnecessarily.

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Jeremy Young (UK)

interesting point (and sorry that comment got a slow reply), the median suture is clearly visible in proximal electrons micrographs and typically appears as a dark line in the light microscope. So it is usually a useful feature but I guess it can get obscured with some types of preservation. Equally relevant from reviewing the other species in this group it seems all the species with a disjunct bar can show this feature, although it is not normally as clear as with H. lophota.

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Simun Ascic (Zagreb University, Croatia)
Is this \Helicosphaera lophota", on first image, maybe H. bramlettei?

[I am not sure now which image this comment refered to - but some intermediate speciemens between these taxa do seem to occur - JRY March 2014]"""
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