Nannotax3 - ntax_cenozoic - H. lophota group Nannotax3 - ntax_cenozoic - H. lophota group

H. lophota group


Classification: ntax_cenozoic -> 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 (time control age-window is: 0-800Ma)
blanket confined to central area
Helicosphaera clarissima
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.
Helicosphaera compacta
Elliptical Helicosphaera with well defined birefringent blanket in XPL and narrow central area spanned by a conjunct bar.
Helicosphaera disrupta
Like H. compacta but with a truncated flange
Helicosphaera reticulata
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.
Helicosphaera robinsoniae
Large Helicosphaera with birefringent blanket, indistinct but disjunct, birefringent oblique bar, and anterior spur.
blanket overlaps flange
Helicosphaera bramlettei
Elliptical Helicosphaera with relatively wide central area spanned by a broad, oblique disjunct bar.
Helicosphaera lophota
Elliptical, oblong or reniform Helicosphaera with wide flange and central area spanned by a broad, near-longitudinal disjunct bar usually with distinct median suture.
Helicosphaera papillata
Broadly rhomboidal; blanket with numerous perforations extending over the central area and covering the bar
Helicosphaera prolixa
Large, broadly elliptical Helicosphaera;  central area narrow, with oblique, disjunct, broad bar. The coccolith is relatively birefringent across the width of the rim.
Helicosphaera seminulum
Elliptical Helicosphaera with relatively wide central area spanned by a broad tranverse to slightly-oblique disjunct bar.
Helicosphaera wilcoxonii
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
taxonomic rank: species group

Distinguishing features:
Parent taxon (Helicosphaera): Coccoliths with helical flange; arranged spirally on the coccosphere
This taxon: Paleogene species; flange does not expand into a wing; bar conjunct or disjunct with rim, normally oriented.

Farinacci & Howe catalog pages:

Search data:
Lith size: 8->15µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): at top of NN2 zone (100% up, 19Ma, in Burdigalian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NP12 zone (50.50-53.70Ma, base in Ypresian stage). Data source: Total of ranges 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: 16-6-2024

Taxon Search:
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Short stable page link: https://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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