D. quinqueramus group


Classification: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. quinqueramus 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.,

Distinguishing features: Symmetric typically 5-rayed, late Miocene discoasters; rays curved proximally, without bifurcations; well-developed distal star and usually proximal boss


Daughter taxa: (blue => in age window 0-300Ma)
forms with modest central structures
Variant with distal star but no proximal knob
Symmetrical; central-area, with prominent distal sutural ridges and large proximal boss; rays concavo-convex, with rounded tips. Central area width less than free ray length [or, adjacent rays meet at the central area].
forms with prominent central structures
Intermediate between D. bergennii and D. quinqueramus; central-area 1-2x free ray length [or, adjacent rays separated at central area].
stem-ridges extend beyond central area - long rays
stem-ridges extend beyond central area - short rays
stem-ridges extend beyond central area - very short rays
stem-ridges extend to edge of central area - very short rays
stem-ridges extend to edge of central area - very short rays
no free rays
Variants with different number of rays
3-rayed variant
4-rayed variant
6-rayed variant with short rays
6-rayed variant with long rays

Taxonomy:

Citation: Discoaster quinqueramus group
Rank: species group
Notes & discussion: Species concepts within this group are notoriously confused. There is a clear trend from forms with large ornate central areas toward forms with small simple central areas, but the boundaries of species intergrade and vary between workers. The diagram of different species concepts from the Gulf Coast Taxonomic Equivalency Project (GC-TEP) illustrates this - and see also comments below.
The revision of Blair et al. (2017) has introduced numerous new species, thse are all documented for now, although many workers will prefer to use fewer species.

Farinacci & Howe catalog pages:

Distinguishing features: Symmetric typically 5-rayed, late Miocene discoasters; rays curved proximally, without bifurcations; well-developed distal star and usually proximal boss


Morphology remarks: This set of intergrading species are a distinctive and important component of Late Miocene assemblages.

Search data:
TagsLITHS: nannolith-radiate, star-shaped, RIM: free-rays-long,
CSPH: not known, V-UNITS: all, R-UNITS: none, DETAILS: 1ou,
MetricsLith size: 5->20µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: This group is confined the Late Miocene and Pliocene and the absence of the group is a useful indication of earlier age. Most individual species are also stratigraphically valuable so this is one of the most stratigraphically vauable groups of nannofossils in the entire Cenozoic.
Last occurrence (top): near top of Messinian Stage (86% up, 5.6Ma, in Messinian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Tortonian Stage (77% up, 8.3Ma, in Tortonian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

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


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D. quinqueramus group 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=424Go to Archive.is to create a permanent copy of this page - citation notes



Comments (2)

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Mike Styzen (Noble Energy, US)
The Taxonomic Equivalency Project was mostly concerned with what people in the oil and gas industry in the US called marker taxa. We did this so when we traded data we would know what each other were referring to. Different members of the group interpreted descriptions differently. This group is useful in the late Miocene, and all of us agreed that there were more useful morphotypes than names available for them. Most of the forms illustrated above have extinctions at different horizons. Nobody used all of them, everyone in the group saw all of them but drew the lines between them differently. There was not one person in the group who was more than moderately concerned with how the various morphotypes fit into the three original descriptions. The object was to have more useful taxa (and therefore horizons) not to shoehorn everything we saw into the original 3 species.
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anon
I think propose the lineage and sketches is very good. As for the above sketches, each one on the right there are four names by different authors? As for Fig 4, Discoaster berggrenii ([Da29] Shell, Arco, most others); wht do you mean by most others? most others regard the three as D. berggrenii? I think these are most likely D. quinqueramus as the rays are long and the central area are relatively short. The same puzzle occurs when it comes to Fig 6, all four authours take them as Discoaster bergrennii, while I doubt the central area is big enough just as in Fig 4, what the difference between the two? what is your own view on each Fig?
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anon
Thank you for you introducing the TEP as I know nothing about it. as a worker in the oil and gas industry in China, in my work , I do see all the three species but never serously distinguished as they all appear in the NN11 zone, and suzones like NN11a are not included in my biostratigraphy division. I think your work is very meaningful to improve the biostratigraphy accuracy. For me, I will do some study to see the occurence order of the three species, to see if meet what you have concluded.
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Mike Styzen (Noble Energy, US)
Discoaster quinqueramus/berggrenii plexus: I posted a document with some sketches from the original Gulf Coast Taxonomic Equivalency Project of this group in the forum. 
[this diagram is now incorporated on this page - JRY March 2014]
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