H. recta group


Classification: Coccolithophores -> Zygodiscales -> Helicosphaeraceae -> Helicosphaera -> H. recta 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)
H. orientalis and variant
Helicosphaera orientalis
Small species. Flange ends abruptly, no wing or spur. Central-area with inversely oriented pores.
Helicosphaera pacifica
Like H. orientalis but central-area granular, without well defined pores.
H. obliqua and variants
Helicosphaera obliqua
Large sized, ovoid shape. Only weakly birefringent. Wing ends in spur, central-area with two prominent pores with inverse orientation.
Helicosphaera perch-nielseniae
Like H. obliqua but more rectangular
Helicosphaera lenticulata
Like H. obliqua but more elongate
Helicosphaera elongata
Like H. obliqua but more elongate and rectangular
Helicosphaera theodoridisii
Like H. obliqua but shorter
H. recta and variants
Helicosphaera recta
Large size, sub-rectangular shape. Wing ends in spur, central-area with two large pores separated by narrow conjunct bar.
Helicosphaera bipuncta
Like H. recta but pores very small
Helicosphaera truncata
Like H. recta but pores larger
Other species
Helicosphaera inversasera
Simlar to H. obliqua but flange continuous, without notch
Helicosphaera gertae
Very large, rounded species, with closed central-area, or two narrow slits.

Taxonomy:

Citation: H. recta group of Young (1998)
Rank: species group

Distinguishing features: Late Oligocene to Mid Miocene species; flange terminates abruptly rather than expanding into a wing; blanket largely confined to central area, so flange is dark is dark in cross-polars; bar conjunct with rim, horizontal or inversely oriented.

Farinacci & Howe catalog pages:


Morphology: Distinctive group of Late Oligocene to Mid Miocene Helicosphaera species, with flange terminating abruptly rather than expanding into a wing. Blanket largely confined to central area, so flange is dark is dark in cross-polars. Central area openings usually show inverse orientation (i.e. they point toward the flange termination). Bar conjunct with rim.

Search data:
TagsLITHS:
MetricsLith size: 4->12µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): near top of Messinian Stage (86% up, 5.6Ma, in Messinian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Priabonian Stage (20% up, 37Ma, in Priabonian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 225-265. gs V O


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H. recta group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 24-10-2020

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=638 Go to Archive.is to create a permanent copy of this page - citation notes



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