INA16 Athens - September 2017

Discoaster musicus


Ancestry: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. variabilis group -> Discoaster musicus
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: Similar to D. exilis , but with wide central area and large distal boss, prominent sutural ridges extending between the rays.


Taxonomy:

Citation: Discoaster musicus Stradner, 1959
Rank: Species
Synonyms: Discoaster sanmiguelensis Bukry, 1981
Notes & discussion: D. musicus has, like D. bollii, a well developed central area and distal knob. However, it lacks a proximal knob; the distal knob is lower than in D. bollii; and sutural rays run from it to the edge of the central area. Possibly better considered as a variety of D. exilis.

Farinacci & Howe catalog pages: Discoaster musicus * Discoaster sanmiguelensis *

Short diagnosis: Similar to D. exilis , but with wide central area and large distal boss, prominent sutural ridges extending between the rays.


Morphology remarks: 6-rayed discoaster with bifurcate rays, similar to D. exilis in having complanate rays with triangular tips, but with wide central area and large distal boss with prominent sutural ridges extending between the rays.

Geological Range:
Notes: Confined to NN5 in the Mediterranean (Theodoridis 1984) but ranges into NN6 in the East Pacific (Bukry 1981), distribution probably patchy
Last occurrence (top): within NN6 zone (11.90-13.53Ma, top in Serravallian stage). Data source: Young 1998
First occurrence (base): within NN5 zone (13.53-14.91Ma, base in Langhian stage). Data source: Young 1998

Plot of occurrence data:

References:

Bukry, D., (1981). Pacific coast coccolith stratigraphy between Point Conception and Cabo Orientes, Deep Sea Drilling Project Leg 63. Initial Reports of the Deep Sea Drilling Project, 63: 445-471.

Stradner, H., (1959). First report on the discoasters of the Tertiary of Austria and their stratigraphic use. Proceedings of the Fifth World Petroleum Congress, 1: 1081-1095.

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 musicus by: Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 29-6-2017

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Comments (2)

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Richard Denne (Marathon Oil, Houston, US)
Discoaster musicus large of Denne
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Mike Styzen (Noble Energy, US)
Mike Styzen - In the GOM D. sanmiguelensis is used as a marker and is distinguished as being somewhat smaller than D. musicus with shorter rays. One might argue that what we're using is just a specific morphotype of D. musicus, but in any case it's a distinction that has stratigraphic function. Richard Howe was kind enough to let me use an image of our D. sanmiguelensis concept
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Jeremy Young (NHM, UK)

this raises plenty of issues

1. Commenting on 'missing taxa'. This is potentially a really valuable funtion of Nannotax, i.e. to get us discussing the less universally understood species concepts. I think it is best done at the place where the taxon is missing from - (so I have copied the comment to the D. musicus page).

2. Posting images - as you found out drag & drop works from external websites, which makes for a great way to rapidly discuss taxa. For a more permanent upload, or for image which are not on an external website use Add Image to put the image in a gallery then drag and drop from there. I've reposted theimage to the Disocaster gallery. [NB Image upload by users is not possible with the current software version but I will rapidly upload any images sent to me - JRY March 2014]

3. Morphotypes and species - if all species were nice and discrete then biostrat would be boringly easy. They aren't though: we know from modern assemblages than biologically separate species can produce very similar coccoliths, and biostrat experience tells us that some arbitrary distinctions are useful. The problem is to keep track of the concepts people are using when things get arbitrary, which is one reason why we have the site.

4. musicus vs sanmiguelensis - what is the difference in size and range; (and is there a reason for applying the name sanmiguelensis to the smaller form)?

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