Calcidiscus bicircus


Ancestry: 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,

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:

Citation: Calcidiscus bicircus Bown, 2005
Rank: Species

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:

References:

Bown, P.R., (2005). 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.

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.

Shamrock & Watkins 2008 [sorry, not in our bibliography yet]


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

Taxon
Search
Search term: in module
Advanced
Search




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.
Page 1 of 1
 

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics