Helicosphaera lophota


Ancestry: Coccolithophores -> Zygodiscales -> Helicosphaeraceae -> Helicosphaera -> H. lophota group -> Helicosphaera lophota
Sister taxa: H. clarissima, H. compacta, H. reticulata, H. robinsoniae, H. bramlettei, H. gertae, H. lophota, H. papillata, H. prolixa, H. seminulum, H. wilcoxonii,

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


Taxonomy:

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

Farinacci & Howe catalog pages: Helicosphaera neolophota * Helicosphaera seminulum lophota *

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


Morphology remarks: 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, RIM: wing, CA: bar-diagonal NE-SW, bar-diagonal,
CSPH: ellipsoidal, varimorphic, V-UNITS: distal shield, R-UNITS: blanket, c-str, px-plate, DETAILS: cstr-w-median-ext-line, ca_disjunct, rim-bicyclic, isogyres kinked, isogyres oblique, isogyres separated,
MetricsLith size: 10->15µm;
Sources:
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.

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

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

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.


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Helicosphaera lophota compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-10-2017

Taxon Search:
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AphiaID: 642588 Nomenclatural data on WoRMS
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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