Daughter taxa: (blue => in age window 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:
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:Tags | LITHS: |
Metrics | Lith size: 8->15µm; |
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:
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H. lophota group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-1-2021
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 |