D. quinqueramus group


Ancestry: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. quinqueramus group
Sister taxa: D. brouweri group, D. pentaradiatus group, D. quinqueramus group, D. variabilis group, D. nodifer group, D. lodoensis group, D. multiradiatus group, D. araneus group, D. sp.,

Short diagnosis: Symmetric 5-rayed, late Miocene discoasters; rays curved, without bifurcations; well developed proximal boss


Daughter taxa (blue => in age window 0-300Ma)
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].
Intermediate between D. bergennii and D. quinqueramus; central-area 1-2x free ray length [or, adjacent rays separated at central area].
Like D. berggrenii but central-area very wide (>2x free ray length)/rays stubby.

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.

Farinacci & Howe catalog pages:

Short diagnosis: Symmetric 5-rayed, late Miocene discoasters; rays curved, without bifurcations; well developed proximal boss


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

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): within Messinian Stage (5.33-7.25Ma, top in Messinian stage). Data source: Total of range of species in this database
First occurrence (base): within Tortonian Stage (7.25-11.62Ma, base 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.


Nannotax3 - Coccolithophores - D. quinqueramus group by: Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 29-6-2017

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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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