Polycostella


Classification: Mesozoic -> Braarudosphaerales -> Nannoconaceae -> Polycostella
Sister taxa: Faviconus, Nannoconus, Polycostella,

Distinguishing features: Globular and stellate nannoliths formed of 5-8 segments of stacked elements. Nannoconus-like in side view.  


Daughter taxa: (blue => in age window 0-800Ma)
Medium-sized (5-8 µm) with 6 segments
Small (<5 µm) of 6 segments
Small (<6 µm), globular, formed of 6-8 segments.
Small (<6 µm) form formed of 5 segments
Specimens not identified to species level

Taxonomy:

Citation: Polycostella Thierstein, 1971
Rank: Genus
Type species: Polycostella senaria Thierstein, 1971.

Farinacci & Howe catalog pages: Polycostella *

Distinguishing features: Globular and stellate nannoliths formed of 5-8 segments of stacked elements. Nannoconus-like in side view.  


Morphology remarks: Structure is Nannoconus-like acording to Varol & Bowman (2019), as demonstratedby use of mobile mounts to view the ame specimens in plan and side view. Distinguished rom Nannoconus by being formed of with 5-7 disrcrete segments in plan view. The side view is more Nannoconus-like but with a straight or concave peripher, and no true axial opening.

Geological Range:
Last occurrence (top): in lower part of Berriasian Stage (26% up, 143.5Ma, in Berriasian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Tithonian Stage (32% up, 149.8Ma, in Tithonian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P. R. & Cooper, M. K. E. (1998). Jurassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 34-85. gs

Thierstein, H. R. (1971). Tentative Lower Cretaceous Calcareous Nannoplankton Zonation. Eclogae Geologicae Helvetiae. 64: 459-488. gs

Varol, O. & Bowman, A. R. (2019). Taxonomic revision of selected Late Jurassic (Tithonian) calcareous nannofossils and the application of mobile mounting. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. 291: 65-87. gs


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Polycostella compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-8-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10923 Go to Archive.is to create a permanent copy of this page - citation notes



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