THE DISCOASTER BERGENII -> BERGRENNII -> QUINQUERAMUS LINEAGE

This set of sketches has been knocking around for quite some time. Terri Dunn and I made them from the notes we took at the initial Gulf Coast Taxonomic Equivalency Project (GCTEP) meeting back in the mid 1990s. They are an attempt to document all of the various morphotypes of this group as used by the folks who attended that meeting. At that time, there were three official specific names in use. In 2003 (JNR 25#1) Wuchang Wei added a subspecies - Discoaster berggrenii extensus. Figures 7 and 8 would fit into that taxon. I have mentioned before that I think the designation of that subspecies is unfortunate as there is already a Discoaster extensus (2 actually, one became D. druggii). What is even more unfortunate is that I have already seen reports with D. berggrenii extensus reported as just D. extensus. There are numerous inacuracies in these illustrations, many of which have been pointed out to me over the years, but the basic idea is there. One of the things I hope will happen with the new GCTEP will be to actually get some more photos and names for this group.

Mike Styzen

June 2015 - I have extracted this diagram from a hidden archive, for discussion at the Plymouth Discoaster workshop - and added the coloured columns on the right to illustrate the different species concepts.

From looking at this/after workshop discussions the following points seem to be worth making:

Jeremy Young. June 2015

UPDATE - June 2018. Blair et al. (2017) have provided extended documentation of the D. quinqueramus group based on taxonomic concepts developed in the Gulf of Mexico within BP and associated companies, including description of many new species. I have now added an extra column to compare this scheme with the others. They attach more weight to ratio of central area:free ray hence fig. 6 appears closest to their D. quinqueramus > 15 µm. they also subdivide the form with extended sutural ridges (fig. 7) into types with larger (consutus) and smaller (explicatus) central area. They also decribed forms with 6-rays.


Sketches of different forms Identifications according to different workers Shell
PDI
Exxon
TBS
Mobil
Consensus
BP 2017
dq1 Fig. 1
  • Discoaster quinqueramus ([Da q] Shell), Exxon);
  • Discoaster A (PDI,others);
  • DTR 270(Mobil);
  • D. quinqueramus A (TBS);
  • D. cf. quinqeramus (Arco)
quinq
A
quinq
quinq A
270
quinqueramus
+
reduced
boss
quintatus
dq2

Fig. 2

  • Discoaster berggrenii ([Da 29] (Shell);
  • DTR 441 (Mobil);
  • Discoaster quinqueramus (most others)

bergr
Da 29C
A
quinq
quinq
441
quinqueramus
+
stellate distal boss
quintatus

Fig. 3

  • Discoaster berggrenii ([Da29] Shell);
  • Discoaster A (PDI);
  • DTR 2P (Mobil);
  • Discoaster quinqueramus B (TBS);
  • Discoaster quinqueramus (most others)
bergr
Da 29C
A
quinq
quinq B
2P
quinqueramus
+
stellate
distal boss
quinqueramus
dq4

Fig. 4

  • Discoaster berggrenii ([Da29] Shell, Arco, most others);
  • Discoaster B (PDI); DTR 442 (Mobil);
  • Discoaster berggrenii 001 (Exxon);
  • Discoaster quinqueramus B (TBS);

bergr
Da 29C
B
bergr
001
quinq
B
442
berggrenii
quinqueramus
dq5

Fig. 5

  • Discoaster berggrenii ([Da29] Shell, Arco, most others);
  • Discoaster B (PDI);
  • DTR 2P (Mobil);
  • Discoaster berggrenii 001 (Exxon);
  • Discoaster berggrenii w/o protrusions (TBS)

bergr
Da 29C
B
bergr
001
bergr
w/o
prots
2P
berggrenii berggrenii
dq6


Fig. 6

  • Discoaster berggrenii ([Da29] Shell, );
  • Discoaster B (PDI); DTR 2P (Mobil);
  • Discoaster berggrenii 001 (Exxon);
  • Discoaster berggrenii var A (Arco);
  • Discoaster berggrenii w/o protrusions (TBS)

bergr
Da 29C
B
bergr
001
bergr
w/o
prots
2P
berggrenii ?quinqueramus >15µm
dq7

Fig. 7

  • Discoaster berggrenii ([Da29varC] Shell, most others);
  • Discoaster C (PDI);
  • DTR 443 (Mobil);
  • Discoaster berggrenii 001 (Exxon);
  • Discoaster berggrenii C (TBS);
  • Discoaster berggrenii var B (Arco)
bergr
Da 29C
C
bergr
001
bergr C
443
n. sp.

explicatus & consutus
dq8

Fig. 8

  • Discoaster berggrenii ([Da29varC] Shell, most others);
  • Discoaster C (PDI); DTR 443 (Mobil);
  • Discoaster berggrenii 101 (Exxon);
  • Discoaster berggrenii C (TBS);
  • Discoaster berggrenii var B (Arco)
bergr
Da 29C
C
bergr
101
 bergr C
443
n. sp. explicatus & consutus
dq9

Fig. 9-12


Shell

  • Discoaster bergenii (Da29var) Fig. 9,10;
  • Discoaster bergenii var A (Da29VarA) Fig. 11;
  • Discoaster 7 (Da 7) Fig. 12

Mobil, Exxon, PDI, Arco, most others

  • Questionable Fig. 9,10,11,12

Da29var
?
?
?
?
bergenii
9, 10 bergenii, compactus

11 abrachiatus

12 vinsonii

Comments


Splitting not Lumping

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.


good work

Thank you for 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.


Sat, 20/07/2013 - 01:41 - Nanno

Discoaster quinqueramus-bergrennii-bergenii group

I think propose the lineage and sketches is very good . As for the aboved 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?