H. lophota group


Classification: Coccolithophores -> Zygodiscales -> Helicosphaeraceae -> Helicosphaera -> H. lophota group
Sister taxa: H. carteri group, H. walbersdorfensis group, H. ampliaperta group, H. recta group, H. lophota group, H. sp.,

Daughter taxa: (blue => in age window 0-800Ma)
blanket confined to central area
Large elliptical to almond-shaped Helicosphaera with well defined birefringent blanket in XPL and a central area spanned by a broad, oblique, disjunct birefringent bar.
Elliptical Helicosphaera with well defined birefringent blanket in XPL and narrow central area spanned by a conjunct bar.
Like H. compacta but with a truncated flange
Broadly rhombohedral Helicosphaera with a moderately well-developed spur in some specimens and a broad, oblique (high angled) disjunct bar. Distal surface covered by a blanket with multiple perforations, some large.
Large Helicosphaera with birefringent blanket, indistinct but disjunct, birefringent oblique bar, and anterior spur.
blanket overlaps flange
Elliptical Helicosphaera with relatively wide central area spanned by a broad, oblique disjunct bar.
Elliptical, oblong or reniform Helicosphaera with wide flange and central area spanned by a broad, near-longitudinal disjunct bar usually with distinct median suture.
Broadly rhomboidal; blanket with numerous perforations extending over the central area and covering the bar
Large, broadly elliptical Helicosphaera;  central area narrow, with oblique, disjunct, broad bar. The coccolith is relatively birefringent across the width of the rim.
Elliptical Helicosphaera with relatively wide central area spanned by a broad tranverse to slightly-oblique disjunct bar.
Helicosphaera with relatively wide central area spanned by a broad tranverse to slightly-oblique disjunct bar and a flange that ends in a spur.

Taxonomy:

Citation: H. lophota group
Rank: species group

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

Farinacci & Howe catalog pages:

Search data:
TagsRIM: wing,
CSPH: ellipsoidal-----, varimorphic, V-UNITS: distal shield, R-UNITS: blanket, c-str, px-plate, DETAILS: isogyres kinked, isogyres oblique, isogyres separated,
MetricsLith size: 8->15µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): in lower part of Burdigalian Stage (32% up, 19Ma, in Burdigalian stage). 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:


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H. lophota group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 2-4-2020

Taxon Search:
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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=637 Go to Archive.is to create a permanent copy of this page - citation notes



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