Daughter taxa (time control age-window is: 0-800Ma) | Granddaughter taxa | ||||
Discoaster pentaradiatus Ray tips with acute bifurcations; strongly concavo-convex; birefringent | |||||
Discoaster prepentaradiatus Symmetric with bifurcations; rays planar and all show similar birefringence. | Discoaster prepentaradiatus prepentaradiatus Discoaster prepentaradiatus plautus Discoaster styzenii Discoaster trifolius | ||||
Discoaster hamatus 5-rayed; ray tips with clockwise deflected (in distal view) proximal extensions. | |||||
Discoaster bellus Symmetric 5-rayed species with simple ray tips |
Taxonomy:
Distinguishing features:
Parent taxon (Discoaster): Radiate nannoliths with each ray formed of a discrete crystal-unit, with the c-axes perpendicular to the nannolith surface.
This taxon: Symmetric 5-rayed, late Neogene, discoasters without large proximal boss
Farinacci & Howe catalog pages:
Morphology:
Lith size: 7->20µm; |
Geological Range:
Notes: This group is confined the Late Miocene and Pliocene and the absence of the group is a useful indication of earlier age. Most individual species are also stratigraphically valuable so this is one of the most stratigraphically vauable groups of nannofossils in the entire Cenozoic.
Last occurrence (top): at top of NN17 zone (100% up, 2.4Ma, in Gelasian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NN8 zone (10.55-10.89Ma, base in Tortonian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 225-265. gs References:
D. pentaradiatus group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 11-9-2024
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=423 Go to Archive.is to create a permanent copy of this page - citation notes |
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