D. brouweri group


Classification: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. brouweri group
Sister taxa: D. brouweri group, D. pentaradiatus group, D. quinqueramus group, D. variabilis group, D. exilis group, D. musicus group, D. deflandrei group, D. nodifer group, D. lodoensis group, D. multiradiatus group, D. araneus group, D. sp.,

Daughter taxa: (blue => in age window 0-800Ma)
D. brouweri and variants
Symmetric 3-rayed variety of D. brouweri.
Symmetric 4-rayed variety of D. brouweri.
Asymmetric 5-rayed variety of D. brouweri.
Ray tips non-bifurcate but with marked proximal extensions giving it a distinctive concavo-convex form.
Distinctive species
6 rayed with complanate rays; very large stellate proximal boss; and small distal boss.
6-rayed with asymmetric ray tips; one bifurcation extended proximally
Species with 6 flat rays and simple terminations
Similar to D. brouweri but ray tips simple, without proximal extensions.
Very large (>20µm), flat discoaster, with simple ray tips.
Flat and  with simple ray terminations, medium to large.
Flat, with simple ray terminations, tapering was and large central area.
small 6-rayed discoaster with stubby arms.
poorly preserved 6-rayed discoasters without bifurcations

Taxonomy:

Citation: D. brouweri group of Young 1998
Rank: species group
Notes & discussion: Three sets of species are recognised in the table.
  1. D. brouweri and vatiants with reduced numbers of rays. The forms with reduced numbers of rays have well-established shorter ranges than the classic 6-rayed form and are conventionally treated as discrete species.
  2. Two well-established distinctive species - D. altus a mid Pliocene species with a massive central boss, and D. calcaris with offset ray tips.
  3. Several species with simple ray terminations, as opposed to the downturned ray tips of D. brouweri. None of these species are well-established and it is unclear whether they are  useful or not. Following the work of  Browning et al. 2017 and de Kaenel et al. 2017 we have included more of these here than we did previously.

Distinguishing features: 6-rayed discoasters without bifurcations, and closely related forms with 3 to 5 rays.

Farinacci & Howe catalog pages:

Search data:
TagsLITHS: nannolith-radiate, star-shaped,
CSPH: not known, V-UNITS: all, R-UNITS: none, DETAILS: 1ou,
MetricsLith size: 5->30µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: This group is characteristic of the Late Miocene and Pliocene but the first appearance of the group is not of much value since it is gradational with disolution specimens resembling D. brouweri can be found in older sediments.
Last occurrence (top): near top of Gelasian Stage (85% up, 1.9Ma, in Gelasian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Aquitanian Stage (0% up, 23Ma, in Aquitanian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

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

de Kaenel, E., Bergen, J. A., Browning, E., Blair, S. A. & Boesiger, T. M. (2017). Uppermost Oligocene to Middle Miocene Discoaster and Catinaster taxonomy and stratigraphy in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research. 37(2-3): 215-244. gs

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


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D. brouweri group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-10-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=419 Go to Archive.is to create a permanent copy of this page - citation notes



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