INA16 Athens - September 2017

Calcidiscus bicircus

Short diagnosis: 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:

Farinacci & Howe catalog pages: Calcidiscus bicircus *

Short diagnosis: 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.

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 2008

Plot of occurrence data:

• Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
• Triangles indicate an event for which a precise placement has been suggested
• Histogram - Neptune occurrence data from DSDP and ODP proceedings. Interpret with caution & read these notes
• Taxon plotted: , synonyms included - No occurrences of Calcidiscus bicircus recorded in Neptune database Parent: C. pacificanus group

Nannotax3 - Coccolithophores - Calcidiscus bicircus by: Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 29-6-2017

Weblink to this page: ina.tmsoc.org/Nannotax3/link.php?taxon=Calcidiscus_bicircus Cite this page - citation notes

Comments (1)

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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.

27th January 2011 12:00am

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.

24th March 2014 5:37pm

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