C. gigas group


Classification: Coccolithophores -> Coccolithales -> Coccolithaceae -> Coccolithus -> C. gigas group
Sister taxa: C. pelagicus group, C. formosus group, C. biparteoperculatus group, C. gigas group, C. sp.,

Daughter taxa: (blue => in age window 0-800Ma)
Very large (~>15µm) Coccolithus-like coccolith with narrow central area crossed by broad diagonal bars.
Broadly elliptical; central area width similar to shield width, spanned by conspicuous axial crossbars.

Very large (>14 µm) Coccolithus with wide central area and narrow, axial to slightly rotated cross bars.
Large to very large (7-15 µm) Coccolithus with a narrow central area and axial cross bars.

Taxonomy:

Citation: Coccolithus gigas group, sensu Bown & Newsam 2017
Rank: sub-genus
Notes & discussion: C. hulliae was not included in this group by Bown & Newsam (2017) in order to draw attnetion to the fact that there is a distinctive group of larger coccoliths withcrossbars in the mid Eocene. howevr, for practical purposes it is convinient to include since it overlaps in range, size and morhology with the other members of the group. [my interpretation - JRY 2017]

Distinguishing features: Large to very large; central areas narrow to moderately-wide, with crossbars that are conspicuous in LM.

Farinacci & Howe catalog pages: ,


Morphology remarks: Large to very large Coccolithus coccoliths with narrow to moderately-wide central areas spanned by crossbars that are conspicuous in light microscope.
Remarks: These coccoliths have previously been variously classified within the genera Cruciplacolithus, Chiasmolithus and Coccolithus but appear to represent a coherent lineage with stratigraphic range restricted to the mid-part of the Eocene (Zones 14–16). The inclusion of these species within the genus Coccolithus is consistent with the extant Coccolithus species, which can also produce central area bars and crosses.
Included species: C. gigas, C. mutatus, C. opdykei, C. staurion. [Bown& Newam 2017]

Search data:
TagsLITHS: placolith, elliptical, RIM: psh-bicyclic, CA: cross,
CSPH: spherical, monomorphic, V-UNITS: distal shield, px-tube, R-UNITS: c-str, ds-tube, prox shield, DETAILS: ca_disjunct, rim-bicyclic, isogyres oblique,
MetricsLith size: 6->24µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

See also: Cruciplacolithus ;Coccolithus tenuiforatus ;

Geological Range:
Last occurrence (top): in upper part of Lutetian Stage (74% up, 42.9Ma, in Lutetian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Thanetian Stage (62% up, 57.2Ma, in Thanetian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P. R. & Newsam, C. (2017). Calcareous nannofossils from the Eocene North Atlantic Ocean (IODP Expedition 342 Sites U1403–1411). Journal of Nannoplankton Research. 37(1): 25-60. gs


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C. gigas group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-7-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=167 Go to Archive.is to create a permanent copy of this page - citation notes



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