C. bidens group


Classification: ntax_cenozoic -> Coccolithales -> Coccolithaceae -> Chiasmolithus -> C. bidens group
Sister taxa: C. bidens group, C. consuetus group, C. sp.

Daughter taxa (time control age-window is: 0-800Ma)
Chiasmolithus altus
Large Chiasmolithus with broad centro-distal cycle and broad, straight diagonal bars that are birefringent and typically show median extinction lines. The bars meet at relatively high angle, i.e. ~90 degrees and are not offset.
Chiasmolithus bidens
Chiasmolithus with broad centro-distal cycle, narrow central area and broad diagonal bars, two that are offset where they meet. Bars are birefringent and typically show median extinction lines. Often have two small conjunct projections (teeth) extending into the central area along the short axis (hence the name "bidens", which means two teeth).
Chiasmolithus edentulus
Small Chiasmolithus with broad centro-distal cycle, narrow central area and broad diagonal bars, two that are offset where they meet.
Chiasmolithus eoaltus
Large Chiasmolithus with broad centro-distal cycle and relatively straight diagonal bars.
Chiasmolithus eograndis
Large Chiasmolithus with broad centro-distal cycle, relatively wide central area and diagonal bars, two of which are strongly curved and offset.
Chiasmolithus expansus
Large to very large Chiasmolithus with relatively narrow shields, broad centro-distal cycle, wide central area and curving diagonal bars, which form an H shape.
Chiasmolithus grandis
Very large Chiasmolithus (>15 µm) with broad centro-distal cycle, wide central area and broad, curving diagonal bars, which form an H shape. Usually displays four small conjunct ‘teeth’ that project into the central area along the major axes.
Chiasmolithus medius

Chiasmolithus modestus

Chiasmolithus oamaruensis
Large to very large Chiasmolithus with broad centro-distal cycle, wide central area and straight, narrow, symmetrical diagonal bars, which join at a relatively acute angle along the minor axis.
Chiasmolithus solitus
Chiasmolithus with broad centro-distal cycle, wide central area and broad diagonal bars, two that curve and are offset where they meet. Bars are birefringent and may show median extinction lines.

Taxonomy:

Citation: Chiasmolithus bidens group
Rank: species group

Distinguishing features: Upper-tube cycle strongly developed; cross bars with complex construction, median exinction line

Farinacci & Howe catalog pages:


Morphology: The upper tube-cycle is characteristically very well-developed. Typically the distal shield is rather narrow and the inner tube cycle forms a crest around the edge of the shield and then extends inward subhorizontally. Grills often seen in central area

Search data:
TagsLITHS:
MetricsLith size: 5->24µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): in upper part of Chattian Stage (73% up, 24.4Ma, in Chattian stage). Data source: Total of range of species in this database
First occurrence (base): near top of Danian Stage (87% up, 62.2Ma, in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Varol, O. (1992a). Sullivania a new genus of Palaeogene coccoliths. Journal of Micropalaeontology. 11: 141-150. gs V O


nannotaxlogo400px

C. bidens group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 1-3-2021

Taxon Search:
Advanced Search

Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=162 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (0)

No comments yet on this page. Please do add comments if you spot any problems, or have information to share

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics