Large (8-12 µm) Cretarhabdids with relatively broad shields and a central area spanned by tapering, broad, axial cross bars that are strongly birefringent with median extinction lines.
Specimens not identified to species level
Distinguishing features:
Parent taxon (Cretarhabdaceae): Regular placoliths; central-area spanned by elevated distal structure typically with cross bars and central spine.
The distal shield usually weakly bicyclic, with narrow outer-cycle and broad inner-cycle; elements usually radial and non-imbricate. LM image is moderately birefringent. V/R structure unclear.
This taxon: Cretarhabdids with relatively broad shields; central area spanned by a broad axial cross, with strong medial extinction lines.
| Daughter taxa (time control age-window is: 0-800Ma) | Granddaughter taxa | ||||
| | | | Cruciellipsis cuvillieri Large (8-12 µm) Cretarhabdids with relatively broad shields and a central area spanned by tapering, broad, axial cross bars that are strongly birefringent with median extinction lines. | |
| Cruciellipsis sp. Specimens not identified to species level | |||||
Taxonomy:
Farinacci & Howe catalog pages: Cruciellipsis + *
Distinguishing features:
Parent taxon (Cretarhabdaceae): Regular placoliths; central-area spanned by elevated distal structure typically with cross bars and central spine.
The distal shield usually weakly bicyclic, with narrow outer-cycle and broad inner-cycle; elements usually radial and non-imbricate. LM image is moderately birefringent. V/R structure unclear.
This taxon: Cretarhabdids with relatively broad shields; central area spanned by a broad axial cross, with strong medial extinction lines.
Morphology: Cross bright when aligned with polariser, dark at 45° position, with gypsum plate cross shows opposite colours to adjacent rim
| Tags | LITHS: placolith, elliptical, CA: cross-axial, ca_disjunct, grill, process, CROSS-POLARS: rim-unicyclic, R-prominent, |
| Metrics | Lith size: 8->16µm; Data source notes: size range of included species |
Geological Range:
Last occurrence (top): at top of Hauterivian Stage (100% up, 130.8Ma, in Hauterivian 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:
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 Thierstein, H. R. (1971). Tentative Lower Cretaceous Calcareous Nannoplankton Zonation. Eclogae Geologicae Helvetiae. 64: 459-488. gs V O Wind, F. H. & Cepek, P. (1979). Lower Cretaceous calcareous nannoplankton from DSDP Hole 397A (northwest African Margin). Initial Reports of the Deep Sea Drilling Project. 47A: 221-235. gs V OReferences:
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Cruciellipsis compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-1-2022
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10327 Go to Archive.is to create a permanent copy of this page - citation notes |
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