Calcidiscus tropicus


Ancestry: Coccolithophores -> Coccolithales -> Calcidiscaceae -> Calcidiscus -> C. leptoporus group -> Calcidiscus tropicus
Sister taxa: C. gallagheri, C. leptoporus, C. macintyrei, C. pataecus, C. premacintyrei, C. salomonii, C. tropicus,

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


Taxonomy:

Citation: Calcidiscus tropicus (Kamptner, 1955) Varol 1989 sensu Gartner, 1992
Rank: Species
Basionym: Cyclococcolithus tropicus Kamptner, 1955
Variants:
Synonyms:
Notes & discussion: da Gama & Varol (2013) recommended that the name C. tanianus should be used instead of C. tropicus since the type specimen of C. tropicus was >10 µm in size - both species are described form the same Late Miocene sample. We do not think that dividing this group at 10µm is useful other than in the Late Pliocene and so prefer to use C. tropicus in the established sense.

Farinacci & Howe catalog pages: Cyclococcolithus tanianus * Cyclococcolithus tropicus * Cycloperfolithus carlae *

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


Morphology remarks: Not always separated from C. leptoporus. Miocene forms often have a bicyclic proximal shield. In some Pliocene forms a coarse grill occurs in the central opening, this extends to the proximal surface but is formed of V-units . In the Late Pliocene larger forms (>10µm) are separated as C. macintyrei. C. tropicus possibly evolves into C. quadriperforatus.

Search data:
TagsLITHS: placolith, circular, RIM: rim-broad, CA: grill, vacant,
CSPH: spherical, monomorphic, V-UNITS: c-str, distal shield, tube, R-UNITS: prox shield, DETAILS: isogyres oblique, rim-unicyclic,
MetricsLith size: 5->12µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within NN19 zone (0.44-1.93Ma, top in Ionian stage). Data source: Young 1998
First occurrence (base): within NN4 zone (14.91-17.95Ma, base in Burdigalian stage). Data source: Young 1998

Plot of occurrence data:

References:

da Gama, R.O.B.P. & Varol, O., (2013). New Late Oligocene to Miocene Species. Journal of Nannoplankton Research, 33(1): 1-12.

Gartner, S., (1992). Miocene nannofossil chronology in the North Atlantic, DSDP Site 608. Marine Micropaleontology, 18: 307-331.

Janin, M.-C., (1992). Miocene variability of Calcidiscus gr. leptoporus and possible evolutionary relationsip with another Coccolithaceae: Umbiliosphaera gr. sibogae. Bio Systems, 28: 169-178.

Kamptner, E., (1955). Fossile Coccolithineen-Skelettreste aus Insulinde. Eine mikropaläontologische Untersuchung. Koninklijke Nederlandse Akademie van Wetenschappen; Afdeling Natuurkunde Verhandelingen, ser 2, 50: 1-105.

Lehotayova, R. & Priewalder, H., (1978). Cycloperfolithus, eine neue Nannofossil-Gattung aus dem Badenien der Zentralen Paratethys. In: Papp, A. et al. (Editors), Chronostratigraphie und Neostratotypen -Miozan N, BadenieM-4: IGCP Proj. 25, pp. 486-489.

Perch-Nielsen, K., (1984). Validation of new combinations. Newsletter of the International Nannoplankton Association, 6(1): 42-46.

Stradner, H. & Fuchs, R., (1980). Über Nannoplanktonvorkommen im Sarmatien (Ober-Miozän) der Zentralen Paratethys in Niederösterreichung im Burgenland. Beitrage zur Paläontologie von Österreich, 7: 251-279.

Varol, O., (1989). Calcareous nannofossil study of the central and western Solomon Islands., Circum-Pacific Council for Energy and Mineral Resources Earth Sciences. Geology and offshore resources of Pacific island arcs, pp. 239-268.

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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Calcidiscus tropicus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-10-2017

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Comments (1)

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Mike Styzen (Noble Energy, US)
In the Gulf of Mexico the LAD of C. carlae (the type with a fine grill in the central area) is used as a marker equivalent in age to the LAD of Discoaster tamalis or slightly younger, depends on who you talk to. If you talk to me, they are equivalent. I found the same co-occurence of these two taxa in the South Pacific in the material from ODP leg 135. The grill is often difficult to discern without the use of phase contrast.
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Richard Denne (Marathon Oil, Houston, US)
Two comments: (1) C. carlae appears to be a valid species, as both its overall range (NN9? to NN16) and abundance patterns (prominent increases in basal NN16/uppermost NN15 and within NN11) are distinct from similar forms, and I have never seen anything that I would have called a C. macintyrei or C. tropicus that had a grill. (2) C. tropicus itself may be a catchall form. There is a very distinct form with a very large central opening and high collar that ranges from NN5/6 to NN11 (see the photo of the specimen labeled 4-16tropicus for a good example) that makes a useful marker within NN11.
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