Discoaster surculus


Ancestry: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. variabilis group -> Discoaster surculus
Sister taxa: D. surculus, D. variabilis, D. exilis, D. deflandrei, D. loeblichii, D. mendomobensis, D. bollii, D. signus, D. petaliformis, D. subsurculus, D. musicus, D. micros, D. challengeri, D. moorei, D. kugleri, D. druggii,

Short diagnosis: 6-rayed with trifurcate ray-tips


Taxonomy:

Citation: Discoaster surculus Martini and Bramlette, 1963
Rank: Species
Notes & discussion: In LM through focusing is often needed to see the ray tip extensions. D. surculus, like D. variabilis, varies considerably in size, and in ray tip morphology. It has not, however, been subdivided.

Farinacci & Howe catalog pages: Discoaster surculus *

Short diagnosis: 6-rayed with trifurcate ray-tips


Morphology remarks: 6-rayed discoaster with trifurcate ray-tips. Similar to D. variabilis but with proximal ray tip extensions giving trifurcate appearance to ray tips. Usually slightly concavo-convex with well-developed central area and showing strong differentiation of proximal and distal surface.

Geological Range:
Notes: Common from NN11A to top NN16. Its last occurrence is used as a datum, the first occurrence is not since it is rather gradational.
Last occurrence (top): at top of NN16 zone (100% up, 2.5Ma, in Gelasian stage). Data source: zonal marker (see e.g. Young 1998)
First occurrence (base): within NN11a subzone (7.42-8.29Ma, base in Tortonian stage). Data source: Young 1998

Plot of occurrence data:

References:

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

Young, J.R., (1998). Neogene. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 225-265.


Nannotax3 - Coccolithophores - Discoaster surculus by: Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 26-3-2017

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Mike Styzen (Noble Energy, US)
Discoaster \9"(Shell US): On the GOM charts I published I have a marker slightly older than the LAD of D. brouweri that I base on the LAD of a species designated as Discoaster 9 (P 1.8). I have always regarded this taxon to be the last gasp of D. surculus, and thus the last gasp of the D. variabilis group. It is a robust six rayed form, usually between 5 and 10 microns with paralell sided rays which have either squared off (overgrown?) or slightly notched tips. If the central area has a knob I call it Discoaster 9a. As I recall both have the same top. The equivalent GOM benthic foram marker is Christellaria S (LAD Lenticulina cf. wallacei) Other workers Have another equivalent Discoaster marker Discoaster \""brouweri A\"". This is not the same bug as Discoaster 9. I'll leave it to someone who actually uses that species to describe it."""
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