Crucibiscutum


Classification: Mesozoic -> Podorhabdales -> Biscutaceae -> Crucibiscutum
Sister taxa: Biscutum, Boletuvelum, Chiastella, Crucibiscutum, Discorhabdus, Gaarderella, Gephyrobiscutum, Helicorhabdus, Jimenezberrocosoia, Seribiscutum, Similiscutum, Sollasites,

Distinguishing features: Elliptical with prominent, birefringent, axial cross.


Daughter taxa: (blue => in age window 0-800Ma)
Crucibiscutum with relatively wide central area, relatively narrow rim and slender-armed axial cross.
Medium-sized (ca 5.5 µm), broadly elliptical Crucibiscutum coccoliths with a relatively wide central-area spanned by off-axial (slightly-rotated) cross-bars.
Small Crucibiscutum with central cross that is only weakly birefringent and does not fill the central area, delineating four perforations that are clearly visible in XPL.
Crucibiscutum with an asymmetrical central cross.
Small Crucibiscutum with narrow central area and birefringent cross. The central cross practically fills the narrow central area, and has the same intensity birefringence as the tube cycle (white).
Specimens not identified to species level
Medium-sized (ca 6.3 µm), broadly elliptical Crucibiscutum coccoliths with a relatively wide central-area spanned by axial cross-bars.

Taxonomy:

Citation: Crucibiscutum Jakubowski, 1986
Rank: Genus
Type species: Cruciplacolithus salebrosus Black, 1971, designated by Jakubowski, 1986.

Farinacci & Howe catalog pages: Crucibiscutum *

Distinguishing features: Elliptical with prominent, birefringent, axial cross.

Geological Range:
Last occurrence (top): at top of Cenomanian Stage (100% up, 93.9Ma, in Cenomanian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Berriasian Stage (0% up, 145Ma, in Berriasian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Black, M. (1971a). Coccoliths of the Speeton Clay and Sutterby Marl. Proceedings of the Yorkshire Geological Society. 38: 381-424. 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

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

Jakubowski, M. (1986). New calcareous nannofossil taxa from the Lower Cretaceous of the North Sea. INA Newsletter. 8: 38-42. gs


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Crucibiscutum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 15-12-2019

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