Nannotax3 - ntax_mesozoic - Rhagodiscus adinfinitus Nannotax3 - ntax_mesozoic - Rhagodiscus adinfinitus

Rhagodiscus adinfinitus


Classification: ntax_mesozoic -> Eiffellithales -> Rhagodiscaceae -> Rhagodiscus -> Rhagodiscus adinfinitus
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: Medium-sized unicyclic loxolith coccoliths with a wide central area spanned by a butterfly-shaped bar with raised, birefringent edges.


Taxonomy:

Citation: Rhagodiscus adinfinitus Bown, 2005
taxonomic rank: Species

Farinacci & Howe catalog pages: R. adinfinitus *

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: Medium-sized unicyclic loxolith coccoliths with a wide central area spanned by a butterfly-shaped bar with raised, birefringent edges.


Morphology:

Similar to Rhagodiscus infinitus, with a central granular plate pierced by two large holes. However, R. infinitus has a plate that extends completely around the central area with distinct circular pores surrounded by raised, birefringent edges; whereas R. adinfinitus has only a broad, flaring bar (butterfly shaped) with raised edges that terminate against the inner edge of the rim. Older specimens are slightly smaller and have less flaring bars. The raised edges of the bar make an angle of ~20°-35° with the transverse axis increasing to 40°-50° in younger specimens. This may represent a shift in morphology toward the R. infinitus morphology.

Size:
Length = 7.2µm

Search data:
LITHS: murolith, elliptical, CA: diagonal cross, plate, process, CROSS-POLARS: R-prominent, rim-unicyclic,
Lith 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:
Last occurrence (top): within Berriasian Stage (137.70-143.10Ma, top in Berriasian stage). Data source: Bown 2005
First occurrence (base): within Berriasian Stage (137.70-143.10Ma, base in Berriasian stage). Data source: Bown 2005

Plot of occurrence data:

References:

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

Rahman, A. & Roth, P. H. (1991). Upper Jurassic calcareous nannofossils from the DSDP Site 534 in the Blake Bahama Basin, western North Atlantic. Eclogae Geologicae Helvetiae. 84: 765-789. gs O

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Rhagodiscus adinfinitus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-10-2024

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