Percivalia


Classification: Mesozoic -> Eiffellithales -> Rhagodiscaceae -> Percivalia
Sister taxa: Calcicalathina, Percivalia, Rhagodiscus, Zebrashapka,

Distinguishing features: Loxolith coccoliths with narrow outer cycle and wide central area filled with a granular plate or bridge, multiple concentric cycles seen on proximal face.


Daughter taxa: (blue => in age window 0-800Ma)


Central area filled by indistinct cross transverse bar of which apears as "bright buttons"
Loxolith coccoliths with narrow outer cycle and wide central area filled with a granular plate. The plate is distinctly smooth and birefringent in XPL and crossed by curving extinction lines.



Central area filled by dark axial cross


Percivalia with a granular central plate in the form of an axial cross.
Specimens not identified to species level

Taxonomy:

Citation: Percivalia Bukry, 1969
Rank: Genus
Type species: Percivalia porosa Bukry, 1969

Farinacci & Howe catalog pages: Percivalia *

Distinguishing features: Loxolith coccoliths with narrow outer cycle and wide central area filled with a granular plate or bridge, multiple concentric cycles seen on proximal face.


Morphology remarks: Rather poorly constrained and applied genus. Nature of the type species, described from EM, is uncertain. Distinction from Rhagodiscus is discussed by Aguado et al. (2000), who noted three differences between the genera:
  1. In proximal view Percivalia shows multiple narrow concentric cycles of elements, rather than a granular structure.
  2. That the central structure shows higher birefirngence in Percivalia than Rhagodiscus
  3. Rhagodiscus species tpyicaly have wide, holowspines whereas in Percivalia they are typically narrow and often solid.

Search data:
TagsLITHS: murolith, elliptical, CA: cross-axial, plate, process, diagonal cross, bar, closed, R-UNITS: R-prominent, DETAILS: rim-unicyclic,
MetricsLith size: 4->9µm;
Sources: size range of included species
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): in lower part of Maastrichtian Stage (36% up, 69.9Ma, in Maastrichtian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Tithonian Stage (0% up, 152.1Ma, in Tithonian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Aguado, R., Company, M. & Tavera, J. M. (2000). The Berriasian/Valanginian boundary in the Mediterranean region: new data from the Caravaca and Cehegín sections, SE Spain. Cretaceous Research. 21: 1-21. 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 :: ::

Bukry, D. (1969). Upper Cretaceous coccoliths from Texas and Europe. The University of Kansas Paleontological Contributions. Article 51 (Protista 2): 1-79. gs :: ::

Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 132-199. gs :: ::


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Percivalia compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 30-5-2020

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10870 Go to Archive.is to create a permanent copy of this page - citation notes



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