Helenea quadrata


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

Distinguishing features: Medium-sized (5-8 µm) broadly elliptical cretarhabdid coccoliths with a central area spanned by diagonal cross bars. The bars may display median black lines under XPL.


Taxonomy:

Citation: Helenea quadrata (Worsley, 1971) Rutledge & Bown in Bown et al., 1998
Rank: Species
Basionym: Watznaueria quadrata Worsley, 1971
Synonyms:
Taxonomic discussion: Unfortunately Black (1971) named a different species Microstaurus quadratus. Worsley's species had priority and Black's species is now named M. staurolithina.

Farinacci & Howe catalog pages: W. quadrata *

Distinguishing features: Medium-sized (5-8 µm) broadly elliptical cretarhabdid coccoliths with a central area spanned by diagonal cross bars. The bars may display median black lines under XPL.

Search data:
TagsLITHS: placolith, elliptical, CA: ca_disjunct, process, diagonal cross, CROSS-POLARS: rim-bicyclic, R-prominent,
MetricsLith size: 6->8µm;
Data source notes: original description & illustrated specimens
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: Bown et al. 1998 recorded FAD in Early Berriasian but a much ealier Tethyan FAD was given by Casellato (2010)
Last occurrence (top): within Late Hauterivian Substage (130.77-133.09Ma, top in Hauterivian stage). Data source: Bown et al. 1998
First occurrence (base): in lower part of NJT13b subzone (20% up, 160.1Ma, in Oxfordian stage). Data source: Casellato 2010, fig 6

Plot of occurrence data:

References:

Bergen, J. A. (1994). Berriasian to early Aptian calcareous nannofossils from the Vocontian Trough (SE France) and Deep Sea Drilling Site 534: new nannofossil taxa and a summary of low-latitude biostratigraphic events. Journal of Nannoplankton Research. 16(2): 59-69. gs V O

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 V O

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

Casellato, C. E. (2010). Calcareous nannofossil biostratigraphy of Upper Callovian - Lower Berriasian successions from the Souhern Alps, North Italy. Rivista Italiana di Paleontologia e Stratigrafia. 116(3): 357-404. gs V O

Jeremiah, J. (2001). A Lower Cretaceous nannofossil zonation for the North Sea Basin. Journal of Micropalaeontology. 20(1): 45-80. gs V O

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 quadrata compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-10-2020

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10502 Go to Archive.is to create a permanent copy of this page - citation notes



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