C. leptoporus group


Ancestry: Coccolithophores -> Coccolithales -> Calcidiscaceae -> Calcidiscus -> C. leptoporus group
Sister taxa: C. leptoporus group, C. pacificanus group, C. sp.,

Short diagnosis: Circular, sub-circular and broadly-eliptical calcidiscid coccoliths with closed central-area.


Daughter taxa (blue => in age window 0-300Ma) Granddaughter taxa
Larger weakly elliptical Calcidiscus species with clearly elliptical central area, opening spanned by a perforated plate.

Species of Calcidiscus producing circular to sub-circular coccoliths with, closed central-area.

Large (>10µm) Pliocene circular species of Calcidiscus with central opening.

Small to medium (~3-8µm), elliptical Calcidiscus coccoliths with a closed central area.

Large, weakly elliptical species of Calcidiscus, central area open, and distinctly elliptical.

Calcidiscus species with small coccoliths (3-6µm) with wide central opening (opening width > shield width)

Species of Calcidiscus producing circular coccoliths with open central-area.

Taxonomy:

Citation: Calcidiscus leptoporus group
Rank: species group

Farinacci & Howe catalog pages:

Short diagnosis: Circular, sub-circular and broadly-eliptical calcidiscid coccoliths with closed central-area.

Geological Range:
Notes: Predominantly Neogene to Modern group with early forms (e.g., Calcidiscus? detectus) recorded in the Oligocene.
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): within Rupelian Stage (28.09-33.89Ma, base in Rupelian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R. & Dunkley Jones, T., (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research, 32(2): 3-51.


Nannotax3 - Coccolithophores - C. leptoporus 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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Simun Ascic (Zagreb University, Croatia)
Is there possibility that C. tropicus and C. leptoporus diverged from same species, in early Miocene? In my analyses I have over 90% of Calcidiscus, in whole preparation, with small open central area, dimensions 5-10?m. I couldn't seen grill in central. It is a Central Paratethyan, probably NN5-NN6! Best regard, Simun Ascic
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Mike Styzen (Noble Energy, US)
Take a look at this article: Knappertsbusch, Michael, 2000; MORPHOLOGIC EVOLUTION OF THE COCCOLITHOPHORID CALCIDISCUS LEPTOPORUS FROM THE EARLY MIOCENE TO RECENT Journal of Paleontology; July 2000; v. 74; no. 4; p. 712-730
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Simun Ascic (Zagreb University, Croatia)
Absolutely helps! I see there is a problem with taxonomy. These specimens have no grid in central area. It seems to me that central area is fully open. That means it's not C. carlae! Entire population have 5-10_m in diameter. Most of them have less than 10_m. They are represented with 90 and more percentage in slides and they are beautifully preserved, even entire coccospheres. There are still: H. carteri, Co. pelagicus, Co. miopelagicus, B. bigelowii, P. multipora, some indeterminable discoasters... I didn't found \classical example"of Calcidiscus leptoporus! This is Paratethyan and there is no sea conditions after NN6! Thank You very much!"""
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Simun Ascic (Zagreb University, Croatia)
I'm not sure we really have a handle on Calcidiscus taxonomy. There appears to be a repeating pattern of large and small forms with more open and closed central areas. Some with the open central areas have a visible grid. For me it boils down to form taxa. If I encountered that specimen I would call it C. tropicus if it was less than 10_m, or C. macintyrei if it was over 10_m. If it had a visible grid in the central area I would call it Cycloperfolithus (probably should be just Calcidiscus) carlae regardless of size. I'm not sure of the utility of splitting C. leptoporus and C. tropicus as they probably are not real biological taxa and do not, in my work, have much stratigraphic significance. C. macintyrei which is just a size thing has a useful top up in NN 19 so I continue to distinguish them all the way through the range just to be consistent. C. carlae (I'm not sure of the biological significance of the visible grid) has a very useful top in NN16, more or less equivalent to Discoaster tamalis. I continue splitting that out for the same reason. All the forms appear to come and go throughout the range of the group. More work is needed. Does this help?
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Mike Styzen (Noble Energy, US)
C. leptoporus/tropicus/macintyrei/carlae: My entirely utilitarian splitting of this group is a little different than above. I must never have seen assemblages young enough to include C. quadriperforatus as I have never seen a member of this group that large younger than C. macintyrei. I must admit that until very recently I never called anything C. tropicus. I did not see any practical reason to split them from C. leptoporus, so anything less than 10µm was recorded as leptoporus. Above 10µm they became C. macintyrei regardless of the openness of the central area. On the other hand, the specimens with a grill in the open central area (C. carlae) are very important to me as they lave a nice LAD in NN 16. Jeremy just calls these C. tropicus with grill... More recently I have been splitting C. tropicus/leptoporus just to make my data blend better with contractor data. As a side note I always call the small sort of dim Calcidiscus C. pataecus, just because they are easy to recognise.
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