Discoaster prepentaradiatus


Classification: ntax_cenozoic -> Discoasterales -> Discoasteraceae -> Discoaster -> D. pentaradiatus group -> Discoaster prepentaradiatus
Sister taxa: D. pentaradiatus, D. prepentaradiatus, D. hamatus, D. bellus

Variants (could also be distinguished informally) (time control age-window is: 0-800Ma)
Discoaster prepentaradiatus prepentaradiatus
Form with slender bifurcations
Discoaster prepentaradiatus plautus
Form with broad bifurcations
Discoaster styzenii
4-rayed D. prepentaradiatus, often asymmetric
Discoaster trifolius
3-rayed D. prepentaradiatus

Taxonomy:

Citation: Discoaster prepentaradiatus Bukry and Percival, 1971
Rank: Species
Variants: As shown in the table above three and four-rayed forms of D. prepentaradiatus occur and species names have ben propsed for them. Likewise forms with robust or delicate biforcations can be spearated. We prefer to regard these as intra-specific varaints of D. prepentaradiatus.
Taxonomic discussion: This species is only superficially similar to D. pentaradiatus. It is complanate, and does not show any birefringence.
Browning et al. (2017) propose subdivision of the species into two sub-species based on bifurcation thickness and two new species based on ray-number. This is probably not biologically justifiable, but may be biostratigraphically useful. They explain that in the Gulf of Mexico a series of events based on these morphotypes can be consistently recognised, and have long been used. However, they also document significant range differences in the Ceara Rise Leg 154 material, so these events may be more useful for regional correlation than long-range biostratigraphy.

Distinguishing features: Symmetric with bifurcations; rays planar and all show similar birefringence.

Farinacci & Howe catalog pages: D. prepentaradiatus + *


Morphology: 5-rayed symmetric discoaster with broad bifurcations; rays planar and all show similar birefringence. The central area is not large but is distinct, there are usually low knobs on both the distal and proximal side.


Phylogenetic relations: The last occurrence of D. prepentaradiatus is close to the first occurrence of D. pentaradiatus but there is no evidence that they are directly related. It is quite possible that D. prepentaradiatus evolved from D. bollii, whilst D. pentaradiatus was independently derived from D. exilis.

Search data:
TagsLITHS: nannolith-radiate, star-shaped, CA: process, CROSS-POLARS: 1ou, V-prominent,
MetricsLith size: 8->20µm; Segments: 5->5;
Data source notes: size from illustrated specs
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: Occurance ends in Zone NN10A
Last occurrence (top): within NN10 zone (8.29-9.53Ma, top in Tortonian stage). Data source: Young 1998
First occurrence (base): within NN9 zone (9.53-10.55Ma, base in Tortonian stage). Data source: Young 1998

Plot of occurrence data:

References:

Bukry, D. & Percival, S. F. (1971). New Tertiary calcareous nannofossils. Tulane Studies in Geology and Paleontology. 8: 123-146. gs V O

de Kaenel, E. & Villa, G. (1996). Oligocene-Miocene calcareous nannofossil biostratigraphy and paleoeecology from the Iberian Abyssal Plain. Proceedings of the Ocean Drilling Program, Scientific Results. 149: 79-145. gs V O

Theodoridis, S. (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin. 32: 1-271. gs V O

Wei, W. (2003). Upper Miocene nannofossil bistratigraphy and taxonomy of Exxon core CH30-43-2 from the Gulf of Mexico. Journal of Nannoplankton Research. 25(1): 17-23. gs V O

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 225-265. gs V O


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Discoaster prepentaradiatus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 9-3-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=495 Go to Archive.is to create a permanent copy of this page - citation notes



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