Discoaster exilis


Classification: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. exilis group -> Discoaster exilis
Sister taxa: D. exilis, D. cauliflorus, D. moorei, D. extensus, D. discissus ⟩⟨ D. bollii ⟩⟨ D. petaliformis, D. signus, D. apetalus

Taxonomy:

Citation: Discoaster exilis Martini and Bramlette, 1963
Rank: Species
Synonyms: The following three speices described from Malta by SEM are probably best interpreted as overgrown D. exilis Browning et al. (2017) separate D. gozoenis from D. exilis on the grounds that the ridge on the proximal surface of the rays of D. exilis is slightly curved (as mentioned inthe oroginial descrition of Martine & Bramlette (1963). However, forms with straight ridges and curved ridges intergrade and have identical ranges (Browning et al. 2017), hence separating them is pointless.   
Variants:
Taxonomic discussion: This is the dominant Middle Miocene discoaster and like D. deflandrei shows considerable variation in size, strength of bifurcations, central area size etc. Only variants with particularly strong central area features have been successfully spearated.

Distinguishing features: Small central-area; usually with weak distal and proximal bosses; bifurcations acutely angled in plan-view

Farinacci & Howe catalog pages: D. exilis * , E. protoexilis * , D. extensus * , D. gozoensis * , D. graviterminatus * , D. prismatica * , D. pugnosa *


Morphology: This is the dominant Middle Miocene discoaster and like D. deflandrei shows considerable variation in size, strength of bifurcations, central area size etc. Only variants with particularly strong central area features have been successfully spearated.

Search data:
TagsLITHS: nannolith-radiate, star-shaped, CA: process, CROSS-POLARS: 1ou, V-prominent,
MetricsLith size: 8->20µm; Segments: 6->6;
Data source notes: size from OD & illustrated specs
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within NN9 zone (9.53-10.55Ma, top in Tortonian stage). Data source: Young 1998
First occurrence (base): within NN4 zone (14.91-17.95Ma, base in Burdigalian stage). Data source: Young 1998

Plot of occurrence data:

References:

Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs V O

Browning, E., Bergen, J. A., Blair, S. A., Boesiger, T. M. & de Kaenel, E. (2017). Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research. 37(2-3): 189-214. 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

Gartner, S. (1967a). Calcareous nannofossils from Neogene of Trinidad, Jamaica, and Gulf of Mexico. University of Kansas Paleontological Contributions, Papers. 29: 1-7. gs V O

Martini, E. & Bramlette, M. N. (1963). Calcareous nannoplankton from the experimental Mohole drilling. Journal of Paleontology. 37(4): 845-855. gs

Müller, C. (1974b). Calcareous nannoplankton, Leg 25 (Western Indian Ocean). Initial Reports of the Deep Sea Drilling Project. 25: 579-633. 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 exilis compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-10-2020

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=468 Go to Archive.is to create a permanent copy of this page - citation notes



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