Calcidiscus bicircus


Classification: Coccolithophores -> Coccolithales -> Calcidiscaceae -> Calcidiscus -> C. pacificanus group -> Calcidiscus bicircus
Sister taxa: C. bicircus, C. gerrardii, C. pacificanus, C. parvicrucis, C. parvus, C. scullyae, C. kamikurii,

Distinguishing features: Medium to large (5-9 µm) circular-subcircular placoliths with a non-birefringent distal shield and narrow to closed central area surrounded by a narrow, bright tube cycle.


Taxonomy:

Citation: Calcidiscus bicircus Bown, 2005
Rank: Species

Farinacci & Howe catalog pages: Calcidiscus bicircus *

Distinguishing features: Medium to large (5-9 µm) circular-subcircular placoliths with a non-birefringent distal shield and narrow to closed central area surrounded by a narrow, bright tube cycle.

Search data:
TagsLITHS: placolith, elliptical, sub-circular, RIM: rim-broad, CA: Placoliths: closed,
CSPH: spherical, monomorphic, V-UNITS: distal shield, tube, R-UNITS: prox shield, DETAILS: rim-bicyclic, isogyres oblique,
MetricsLith size: 5->9µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within NP17 zone (37.32-40.40Ma, top in Priabonian stage). Data source: Bown et al., 2007
First occurrence (base): within NP12 zone (50.50-53.70Ma, base in Ypresian stage). Data source: Shamrock & Watkins 2012

Plot of occurrence data:

  • (NB There is no histogram as there are no occurrence records for the taxon in the Neptune database) Parent: C. pacificanus group

    References:

    Bown, P. R. (2005d). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research. 27(1): 21-95. gs

    Bown, P. R., Dunkley-Jones, T. & Young, J. R. (2007). Umbilicosphaera jordanii Bown 2005 from the Paleogene of Tanzania: confirmation of generic assignment and a Paleocene origination for the family Calcidiscaceae. Journal of Nannoplankton Research. 29(1): 25-30. gs

    Shamrock, J. L. & Watkins, D. K. (2012). Eocene calcareous nannofossil biostratigraphy and community structure from Exmouth Plateau, Eastern Indian Ocean (ODP Site 762). Stratigraphy. 9(1): 1-11. gs

    nannotaxlogo400px

    Calcidiscus bicircus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 17-6-2019

    Taxon Search:
    		Advanced Search

    Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=175 Go to Archive.is to create a permanent copy of this page - citation notes
    Powered by Mikrotax taxonomy content management system developed by Jeremy Young


    Comments (1)

    Sort By
    Page 1 of 1
     
    Gravatar
    Enis Kemal Sagular (Suleyman Demirel University, Turkey)
    Its images seem to Biscutum blackii from Late Cretaceous species. If being so and found within NP14-NP17 zone assemblage, it may have been reworked from old sediments.
    Gravatar
    Jeremy Young (UCL, UK)
    C. bicircus certainly does resemble Biscutum but it occurs in Tanzania in sites with negligible reworking and has a consistent range there so it probably is an example of homoeomorphy not reworking.
    Notify Me
    Page 1 of 1
     
    Share a link to this comment

    Add Comment

    * Required information
    1000
    Captcha Image
    Powered by Commentics