Discoaster mediosus


Classification: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. nodifer group -> Discoaster mediosus
Sister taxa: D. cruciformis, D. colletii, D. gemmifer, D. mediosus, D. binodosus, D. nodifer, D. distinctus, D. septemradiatus, D. tanii, D. tani ornatus, D. istanbulensis, D. martinii, D. williamsii, D. backmanii, D. okadai,

Distinguishing features: ≥8 near-parallel-sided rays with rounded to pointed tips that radiate with little free length from a large circular central area. May show inter-ray ridges, a low central boss, and the development of nodes towards the ray tips.


Taxonomy:

Citation: Discoaster mediosus Bramlette & Sullivan, 1961
Rank: Species
Variants: Discoaster minimus Sullivan 1964 - smaller and with fewer rays (Aubry 1984)
Notes & discussion: Discoaster mediosus and Discoaster binodosus intergrade but can be distinguished as follows: D. mediosus usually has ten rays or more, with free rays less than half the length of the central area; D. binodosus usually has 8 rays with longer free length and prominent lateral nodes and pointed ray tips.

Farinacci & Howe catalog pages: Discoaster mediosus * Discoaster minimus *

Distinguishing features: ≥8 near-parallel-sided rays with rounded to pointed tips that radiate with little free length from a large circular central area. May show inter-ray ridges, a low central boss, and the development of nodes towards the ray tips.


Morphology remarks: Typically 8-10 rays but can have more.

Search data:
TagsLITHS: nannolith-radiate, star-shaped, RIM: free-rays-long,
CSPH: not known, V-UNITS: all, R-UNITS: none, DETAILS: 1ou,
MetricsLith size: 11->21┬Ám; Segments: 7->9;
Sources: 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 NP10 zone (54.17-55.86Ma, top in Ypresian stage). Data source: PRB entry to Nannotax
First occurrence (base): within NP7 zone (58.70-58.97Ma, base in Thanetian stage). Data source: PRB entry to Nannotax

Plot of occurrence data:

  • 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 mediosus, synonyms included - Discoaster mediosus; space-time plot :: Samples map :: Parent: D. nodifer group

    References:

    Aubry, M.-P., (1984). Handbook of Cenozoic calcareous nannoplankton. Book 1: Ortholithae (Discoasters). Micropaleontology Press, American Museum of Natural History, New York, 266 pp.

    Bramlette, M.N. & Sullivan, F.R., (1961). Coccolithophorids and related nannoplankton of the Early Tertiary in California. Micropaleontology, 7(129-188).


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    Discoaster mediosus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 17-12-2018

    Taxon Search:
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    Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=480Go to Archive.is to create a permanent copy of this page - citation notes



    Comments (1)

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    Rui da Gama

    "Short diagnosis: 8-10 near-parallel-sided rays" - several images provided herein show more than 10 rays

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    Jeremy Young

    good point - clearly the name is applied to forms with 11 or 12 rays, I will change the short diagnosis to >8 rays.

    Thanks for pointing his out

    Jeremy

    Page 1 of 1
     

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