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Coccolithales
(8)
Coccolithales (2)
Calcidiscaceae (5)
Coccolithaceae (6)
Description: 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.
Remarks: 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.
Range: Confined to NN5 in the Mediterranean (Theodoridis 1984) but ranges into NN6 in the East Pacific (Bukry 1981), distribution probably patchy
Synonym: Discoaster sanmiguelensis Bukry, 1981
- 381 reads
- nanno-taxonomy
issues raised
this raises plenty of issues
1. Commenting on 'missing taxa'. This is potentialy a realy valuable funtion of Nannotax, i.e.to get us discussing the less universally understood species concepts. I think it is best done t 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 wihch are not an externl 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.
3. Morphotypes and species - if all species were nice and discrete then biostrat would be boringly easy. They aren't: we know from modern assemblages than biologically separate species can produce very similar coccolith, and biostratexperience 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 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).
Discoaster sanmiguelensis
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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