Nannotax3 - ntax_mesozoic - N. abundans group

N. abundans group


Classification: ntax_mesozoic -> Braarudosphaerales -> Nannoconaceae -> Nannoconus -> N. abundans group
Sister taxa: N. steinmannii group, N. kamptneri group, N. abundans group, N. truittii group, N. circularis group, N. compressus group, Nannoconus - atypical, N. sp.

Distinguishing features:
Parent taxon (Nannoconus): Conical, globular or cylindrical nannoliths composed of plates spirally-arranged around an axial cavity (~>1µm in width) or canal (~<1µm in width). Plate c-axes are arranged tangentially to the longitudinal axis.
This taxon: Cylindrical nannoconids with thin, low-angled wall cycles and relatively narrow canal (ct < wt); also may have apical and/or antapical flanges and/or bulbous base


Daughter taxa (time control age-window is: 0-800Ma)
Nannoconus abundans
Cylindrical nannoconids with apical flange. A smaller flange may also be present at the basal end. Wall cycles are thin and low angled, and the canal is relatively narrow.
Nannoconus alvus

Nannoconus borealis
cylindrical ‘apical’ part and an expanded, bulbous base (height typically >x2 width)
Nannoconus concavus

Nannoconus inornatus
squat, cylindrical; without flanges
Nannoconus troelsenii
Squat cyclindrical Nannoconus with incomplete central-canal, shows central extinction cross in plan view.

Taxonomy:

Citation: N. abundans group
Rank: species group

Taxonomic discussion:
informal grouping first used here

Farinacci & Howe catalog pages: N. abundans group [no catalog entry yet]

Distinguishing features:
Parent taxon (Nannoconus): Conical, globular or cylindrical nannoliths composed of plates spirally-arranged around an axial cavity (~>1µm in width) or canal (~<1µm in width). Plate c-axes are arranged tangentially to the longitudinal axis.
This taxon: Cylindrical nannoconids with thin, low-angled wall cycles and relatively narrow canal (ct < wt); also may have apical and/or antapical flanges and/or bulbous base

Search data:
TagsLITHS: nannolith-radiate, circular, cylindrical, hollow, CA: vacant, CROSS-POLARS: T-prominent,
MetricsLith size: 4->25µm;
Data source notes: size range of included species
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): at top of Aptian Stage (100% up, 113Ma, in Aptian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Berriasian Stage (55% up, 141.9Ma, in Berriasian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Early Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gs

Caratini, C. (1963). Contribution à l'étude des coccolithes du Cénomanien supérieur et du Turonien de la région de Rouen. PhD thesis, Université d'Alger, Faculté des Sciences, Publication du Laboratoire de Géologique Appliquée. -. gs


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N. abundans group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 9-12-2021

Taxon Search:
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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10710 Go to Archive.is to create a permanent copy of this page - citation notes



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