Nannotax3 - ntax_cenozoic - D. quinqueramus group Nannotax3 - ntax_cenozoic - D. quinqueramus group

D. quinqueramus group


Classification: ntax_cenozoic -> 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.

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Discoaster quinqueramus
modest central structures and long free rays
Discoaster quintatus
Discoaster newellii
Discoaster tetracladus
Discoaster hexaramus
Discoaster prolixus

Discoaster berggrenii
prominent central structures and short free rays, stem-ridges confined to central area

Discoaster consutus
prominent central structures and short free rays, stem-ridges extend beyond central area
Discoaster explicatus

Discoaster bergenii
very short free rays
Discoaster compactus
Discoaster vinsonii
Discoaster abrachiatus

Taxonomy:

Citation: Discoaster quinqueramus group
taxonomic rank: species group
Taxonomic 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.

Distinguishing features:
Parent taxon (Discoaster): Radiate nannoliths with each ray formed of a discrete crystal-unit, with the c-axes perpendicular to the nannolith surface.
This taxon: Symmetric typically 5-rayed, late Miocene discoasters; rays curved proximally, without bifurcations; well-developed distal star and usually proximal boss

Farinacci & Howe catalog pages:


Morphology:

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

Search data:
Lith size: 5->20µm;
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): at top of NN12 zone (100% up, 5.1Ma, in Zanclean stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NN10 zone (8.29-9.53Ma, base in Tortonian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:

References:

Raffi, I., Backman, J. & Rio, D. (1998). Evolutionary trends of tropical calcareous nannofossils in the late Neogene. Marine Micropaleontology. 35(1): 17-41. gs

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 225-265. gs

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D. quinqueramus group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 10-12-2024

Taxon Search:
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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=424 Go to Archive.is to create a permanent copy of this page - citation notes
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Comments (4)

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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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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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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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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]