Nannotax3 - ntax_mesozoic - Nannoconus troelsenii

Nannoconus troelsenii


Classification: ntax_mesozoic -> Braarudosphaerales -> Nannoconaceae -> Nannoconus -> N. abundans group -> Nannoconus troelsenii
Sister taxa: N. abundans, N. alvus, N. borealis, N. concavus, N. inornatus, N. troelsenii

Distinguishing features:
Parent taxon (N. abundans group): 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
This taxon: Squat cyclindrical Nannoconus with incomplete central-canal, shows central extinction cross in plan view.


Taxonomy:

Citation: Nannoconus troelsenii Alves, Lima & Shimabukuro 2017
Rank: Species

Farinacci & Howe catalog pages: N. troelsenii *

Distinguishing features:
Parent taxon (N. abundans group): 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
This taxon: Squat cyclindrical Nannoconus with incomplete central-canal, shows central extinction cross in plan view.


Morphology:

Relatively short (height < width), cylindrical Nannoconus. In side view this species has a rectangular outline with parallel sides. In plan view the rim is approximately half the width of the central-area and the central-area comprises a depression rather than a cavity, which, in XPL, shows cross-shaped extinction lines that fill the central-area depression.

Differentiation: Distinguished from other Nannoconus species by the combination of its short, rectangular outline and the central-area depression and cross-shaped extinction lines. This diagnostic feature can be considered distinctive of this species, along with other characteristic features in longitudinal view, such as the relatively thick wall and a height less than the diameter [Alves et al. 2017]

Size:
Height = 2–4μm; Width = 4–12μm; Central-area = 1.5–3μm; Rim = 1.5–3μm.[Alves et al. 2017]

Search data:
TagsLITHS: nannolith-radiate, circular, cylindrical, hollow, CA: vacant, CROSS-POLARS: T-prominent,
MetricsLith size: 4->12µm;
Data source notes: original description
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: At present, the top of Nannoconus troelsenii coincides with the extinctions of Nannoconus quadriangulus subsp. apertus and Nannoconus quadriangulus subsp. quadriangulus, which were described as being restricted to the Aptian (Deflandre & Deflandre-Rigaud, 1967; Barrier, 1977; Deres & Achéritéguy, 1980, and Perch-Nielsen, 1985). [Alves et al. 2017]
Last occurrence (top): within CC7 zone (112.95-126.40Ma, top in Aptian stage). Data source: Alves et al. 2017
First occurrence (base): within CC7 zone (112.95-126.40Ma, base in Barremian stage). Data source: Alves et al. 2017

Plot of occurrence data:

References:

Alves, C. F., Lima, F. H. , de O. & Shimabukoro, S. (2017). New Aptian calcareous nannofossil species from Brazil. Journal of Nannoplankton Research. 37(1): 15-24. gs V O


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Nannoconus troelsenii compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 7-7-2022

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10779 Go to Archive.is to create a permanent copy of this page - citation notes



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