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 :: view :: open

    Bown, P. R. (2005). 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 :: view :: open

    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 :: view :: open

    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 1970. 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: 5-7-2020

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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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