Nannotax3 - ntax_mesozoic - N. circularis group

N. circularis group


Classification: ntax_mesozoic -> Braarudosphaerales -> Nannoconaceae -> Nannoconus -> N. circularis 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 walls (~1.5µm or less), thin, low-angled wall cycles and very wide central cavity (typically ct >3x wt)


Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Nannoconus carniolensis
Barrel-shaped with a distinct constriction/waist towards one end.
N. carniolensis subsp. carniolensis
N. carniolensis subsp. latus

Nannoconus circularis
barrel-shaped to cylindrical (typically similar height and width) with very narrow wall

Nannoconus fragilis
quadriangular, cylindrical, typically similar height and width

Nannoconus grandis
tall (>10 microns), tapering, narrowing at both ends (height ~2x width).

Nannoconus quadratus
cylindrical with midpoint constriction

Taxonomy:

Citation: N. circularis group
Rank: species group

Taxonomic discussion:
informal grouping first used here

Farinacci & Howe catalog pages: N. circularis 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 walls (~1.5µm or less), thin, low-angled wall cycles and very wide central cavity (typically ct >3x wt)

Search data:
TagsLITHS: nannolith-radiate, circular, cylindrical, hollow, CA: vacant, CROSS-POLARS: T-prominent,
MetricsLith size: 3->29µm;
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 Albian Stage (100% up, 100.5Ma, in Albian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Tithonian Stage (0% up, 152.1Ma, in Kimmeridgian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:


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N. circularis group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 28-11-2021

Taxon Search:
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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10711 Go to Archive.is to create a permanent copy of this page - citation notes



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