Nannotax3 - ntax_cenozoic - Discoaster prepentaradiatus

Nannotax3 - ntax_cenozoic - Discoaster prepentaradiatus Nannotax3 - ntax_cenozoic - Discoaster prepentaradiatus

Discoaster prepentaradiatus

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

KPC Discoaster prepentaradiatus.JPG
Theod84 pl12-11.JPG
Young1998_pl08_fig19.JPG
deKaenelVilla96pl06-17.JPG
deKaenelVilla96pl06-19.JPG
deKaenelVilla96pl06-20.JPG
Theod84 pl35-01.JPG
Theod84 pl35-02.JPG
Theod84 pl35-03.JPG
Theod84 pl35-04.JPG
Wei 2003 pl2-03.JPG
Wei 2003 pl2-04.JPG
Young1998_pl08_fig20.JPG
Young1998_010-prepentaradiatus.jpg

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&Percival, 1971

taxonomic 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:
Parent taxon (D. pentaradiatus group): Symmetric 5-rayed, late Neogene, discoasters without large proximal boss
This taxon: 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:

LITHS: nannolith-radiate, star-shaped, CA: process, CROSS-POLARS: 1ou, V-prominent,

Lith 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:

Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
Taxon plotted: Discoaster prepentaradiatus, synonyms included - Discoaster prepentaradiatus;
See also space-time plot :: Samples map :: Parent: D. pentaradiatus group

References:

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

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

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