Nannotax3 - ntax_mesozoic - Percivalia Nannotax3 - ntax_mesozoic - Percivalia

Percivalia


Classification: ntax_mesozoic -> Eiffellithales -> Rhagodiscaceae -> Percivalia
Sister taxa: Percivalia, Rhagodiscus ⟩⟨ Calcicalathina, Zebrashapka

Distinguishing features:
Parent taxon (Rhagodiscaceae): Eiffelithales with V-units forming most of rim (R-units typically thin plates on proximal surface, so LM images are typically unicyclic. Central-areas typically filled by a plate of granular calcite. The central structure may be spine-bearing, perforate or massive.
This taxon: 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 (time control age-window is: 0-800Ma)
Percivalia arata

Percivalia bullata

Percivalia dunkleyjonesii
Central area filled by indistinct cross transverse bar of which apears as "bright buttons"
Percivalia fenestrata
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.
Percivalia hauxtonensis

Percivalia howardii

Percivalia imperfossa

Percivalia pearsonii
Central area filled by dark axial cross
Percivalia pontilitha

Percivalia porosa

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

Taxonomy:

Citation: Percivalia Bukry, 1969
taxonomic rank: Genus
Type species: Percivalia porosa Bukry, 1969

Farinacci & Howe catalog pages: Percivalia *

Distinguishing features:
Parent taxon (Rhagodiscaceae): Eiffelithales with V-units forming most of rim (R-units typically thin plates on proximal surface, so LM images are typically unicyclic. Central-areas typically filled by a plate of granular calcite. The central structure may be spine-bearing, perforate or massive.
This taxon: 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:

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:
LITHS: murolith, elliptical, CA: bar, closed, cross-axial, diagonal cross, plate, process, CROSS-POLARS: R-prominent, rim-unicyclic,
Lith size: 4->9µm;
Data source notes: 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): at top of Early Maastrichtian Substage (100% up, 70.1Ma, in Maastrichtian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within Tithonian Stage (143.10-149.24Ma, base in Tithonian stage). Data source: Total of ranges 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). Lower Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 86-131. gs O

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

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


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Percivalia compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 14-12-2024

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Short stable page link: https://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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