Nannotax3 - ntax_mesozoic - Rhagodiscus robustus

Rhagodiscus robustus


Classification: ntax_mesozoic -> Eiffellithales -> Rhagodiscaceae -> Rhagodiscus -> Rhagodiscus robustus
Sister taxa: R. achlyostaurion, R. amplus, R. angustus, R. asper, R. cepekii, R. dekaenelii, R. infinitus, R. pseudoangustus, R. splendens ⟩⟨ R. adinfinitus, R. gallagheri, R. indistinctus, R. pancostii, R. plebeius, R. robustus, R. sageri, R. sicutclipeus ⟩⟨ R. eboracensis, R. hamptonii, R. reniformis, R. sp.

Distinguishing features:
Parent taxon (Rhagodiscus): Loxolith coccoliths with low rim and central-area filled by a granular plate which may be perforate and/or spine-bearing. In xpl the rim is unicyclic moderately bright, the central area is granular, lacking a clear extinction cross.
This taxon: Large (>8.0 µm) loxolith coccoliths with a broad rim (usually as broad or broader than the central area) and a central area spanned by a granular plate; a relatively large spine or spine base is usually present. The broad and blocky rim shows yellow interference colors under XPL.


Taxonomy:

Citation: Rhagodiscus robustus Bown, 2005
Rank: Species

Farinacci & Howe catalog pages: R. robustus *

Distinguishing features:
Parent taxon (Rhagodiscus): Loxolith coccoliths with low rim and central-area filled by a granular plate which may be perforate and/or spine-bearing. In xpl the rim is unicyclic moderately bright, the central area is granular, lacking a clear extinction cross.
This taxon: Large (>8.0 µm) loxolith coccoliths with a broad rim (usually as broad or broader than the central area) and a central area spanned by a granular plate; a relatively large spine or spine base is usually present. The broad and blocky rim shows yellow interference colors under XPL.


Morphology:

Distinguished from other rhagodiscids by its large size and relatively closed central area, with some specimens resembling the Jurassic coccolith species Crepidolithus crassus. The Albian ‘Crepidolithus burwellensis Black, 1972 (holotype scanning electron micrograph [SEM] only) displays a Crepidolithus-like rim but is small (~4.0 µm) and has an open central area crossed by a transverse bar.

Size:
Holotype length = 8.7µm


Ecology & Biogeography


Biology & life-cycles

Phylogenetic relations

Search data:
LITHS: murolith, elliptical, CA: process, CROSS-POLARS: rim-unicyclic, R-prominent,
Lith size: 8->12µm;
Data source notes: original description & illustrated specimens
The morphological data given here can be used on the advanced search page. See also these notes

See also: Zeugrhabdotus burwellensis - small species with some similarities;

Geological Range:
Last occurrence (top): within NC10a subzone (100.45-103.13Ma, top in Cenomanian stage). Data source: Bown 2005
First occurrence (base): within NC5 zone (126.40-132.87Ma, base in Hauterivian stage). Data source: Bown 2005

Plot of occurrence data:

References:

Black, M. (1972a). British Lower Cretaceous Coccoliths. I-Gault Clay (Part 1). Palaeontographical Society Monograph. 126: 1-48. 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 O

Jeremiah, J. (1996). A proposed Albian to Lower Cenomanian nannofossil biozonation for England and the North Sea Basin. Journal of Micropalaeontology. 15(97-129): -. gs V O


nannotaxlogo400px

Rhagodiscus robustus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 3-12-2022

Taxon Search:
Advanced Search

Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=11030 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (0)

No comments yet on this page. Please do add comments if you spot any problems, or have information to share

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics