Nannotax3 - ntax_mesozoic - Micula clypeata

Micula clypeata


Classification: ntax_mesozoic -> Braarudosphaerales -> Polycyclolithaceae -> Micula -> Micula clypeata
Sister taxa: M. staurophora, M. adumbrata, M. concava, M. cubiformis, M. swastica ⟩⟨ M. murus, M. prinsii ⟩⟨ M. clypeata, M. praemurus, M. premolisilvae, M. sp.

Distinguishing features:
Parent taxon (Micula): Typically cubiform nannoliths usually formed from two superimposed and complexly-intergrown cycles of four pyramidal/blocky elements each
This taxon: Square, flat Micula that appears to be composed of a single cycle of four elements joined along uneven sutures that bend sharply at the their ends. Can appear circular at some focal depths.


Taxonomy:

Citation: Micula clypeata Lees & Bown, 2005
Rank: Species

Farinacci & Howe catalog pages: M. clypeata *

Distinguishing features:
Parent taxon (Micula): Typically cubiform nannoliths usually formed from two superimposed and complexly-intergrown cycles of four pyramidal/blocky elements each
This taxon: Square, flat Micula that appears to be composed of a single cycle of four elements joined along uneven sutures that bend sharply at the their ends. Can appear circular at some focal depths.


Morphology:

A distinctive raised circular area, equal in diameter to the width of the nannolith, lies above the level of the main structure.
A narrow zone of darker birefringence lies along each of the suture lines and broadens towards the corners. 
Much flatter than most other Miculas but with the same crystallographic orientation, i.e. the entire structure is in extinction when the sutures are near-parallel with the polarising directions.
Similar to M. praemurus, particularly at high focus, but differs in having a square 'base' and more complex suture appearance.
Like M. praemurus the chirality of the sutures does not change with focal depth.

Size:
Length/width 5.5-6.5(5.5)µm.

Search data:
LITHS: nannolith-radiate, quadrate, CA: closed,
Lith size: 5->7µm; Segments: 4->4;
Data source notes: original description +/-0.5µm
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within Late Maastrichtian Substage (66.04-69.91Ma, top in Maastrichtian stage). Data source: Lees & Bown 2005
First occurrence (base): within Campanian Stage (72.05-83.64Ma, base in Campanian stage). Data source: Lees & Bown 2005

Plot of occurrence data:

References:

Lees, J. A. & Bown, P. R. (2005). Upper Cretaceous calcareous nannofossil biostratigraphy, ODP Leg 198 (Shatsky Rise, Northwest Pacific Ocean). Proceedings of the Ocean Drilling Program, Scientific Results. 198: 1-60. gs V O


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Micula clypeata compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 25-9-2022

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10675 Go to Archive.is to create a permanent copy of this page - citation notes



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