Helenea conus


Classification: Mesozoic -> Podorhabdales -> Cretarhabdaceae -> Helenea -> Helenea conus
Sister taxa: H. chiastia, H. conus, H. quadrata, H. staurolithina, H. sp.,

Distinguishing features: Medium to large (6-10 µm) subcircular to broadly elliptical; central area with a vaulted axial cross and spine. The bars usually display a dark median line under XPL and flare at their ends.


Taxonomy:

Citation: Helenea conus (Worsley, 1971) Rutledge & Bown in Bown et al., 1998
Rank: Species
Basionym: Staurolithites conus Worsley, 1971
Synonyms: Microstaurus conus (Worsley) Wind and Cepek, 1979

Farinacci & Howe catalog pages: Staurolithites conus *

Distinguishing features: Medium to large (6-10 µm) subcircular to broadly elliptical; central area with a vaulted axial cross and spine. The bars usually display a dark median line under XPL and flare at their ends.


Morphology remarks: The LM appearance of the rim is not particularly typical of Helenea, as it is larger and shows no clear outer cycle; however, the cross bars conform to the generic characteristics. The vaulted nature of the central structure makes focusing on the cross bars difficult.

Search data:
TagsLITHS: placolith, circular, elliptical, CA: cross-axial, process, R-UNITS: R-prominent, DETAILS: ca_disjunct, rim-bicyclic,
MetricsLith size: 6->10µm;
Sources: illustrated specimens
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: Berriasian (Subzone NK2a) - late Valanginian (Subzone NK3b) range given by Bown (2005) for Shatsky Rise sites.
Last occurrence (top): within Early Barremian Substage (129.41-130.77Ma, top in Barremian stage). Data source: Bown et al. 1998
First occurrence (base): within Late Berriasian Substage (139.39-141.93Ma, base in Berriasian stage). Data source: Bown et al. 1998

Plot of occurrence data:

  • Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
  • Note to users in China - the diagram may not plot unless you use a VPN since I use google services on the website. If this is a problem please contact me 谢谢.
  • Taxon plotted: Helenea conus, synonyms included - Helenea conus; Microstaurus conus;
  • space-time plot :: Samples map :: Parent: Helenea

    References:

    Applegate, J. L. & Bergen, J. A. (1988). Cretaceous calcareous nannofossil biostratigraphy of sediments recovered from the Galicia Margin, ODP Leg 103. Proceedings of the Ocean Drilling Program. Scientific Results. 103: 293-348. gs

    Bown, P. R. (2005c). Early to Mid-Cretaceous Calcareous Nannoplankton from the Northwest Pacific Ocean, Leg 198, Shatsky Rise. Proceedings of the Ocean Drilling Program. Scientific Results. 198: 1-82. gs

    Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Early Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gs

    Bralower, T. J., Monechi, S. & Thierstein, H. R. (1989). Calcareous nannofossil zonation of the Jurassic-Cretaceous boundary interval and correlation with the geomagnetic polarity timescale. Marine Micropaleontology. 14: 153-235. gs

    Wind, F. H. & Cepek, P. (1979). Lower Cretaceous calcareous nannoplankton from DSDP Hole 397A (northwest African Margin). Initial Reports of the Deep Sea Drilling Project. 47A: 221-235. gs

    Worsley, T. R. (1971). Calcareous nannofossil zonation of Upper Jurassic and Lower Cretaceous sediments from the Western Atlantic. In, Farinacci, A. (ed.) Proceedings of the Second Planktonic Conference Roma 1971. Edizioni Tecnoscienza, Rome 2: 1301-1321. gs


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    Helenea conus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-2-2020

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    Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10501 Go to Archive.is to create a permanent copy of this page - citation notes



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