Distinguishing features: Medium sized (5-7 µm) with relatively broad shields/relatively narrow central area; in xpl inner rim cycle significantly narrower than the outer rim cycle.
Taxonomy:
Farinacci & Howe catalog pages: T. frankiae *
Distinguishing features: Medium sized (5-7 µm) with relatively broad shields/relatively narrow central area; in xpl inner rim cycle significantly narrower than the outer rim cycle.
Morphology: Bicyclic placolith with relatively broad shields and open central area. In LM XPL the two cycles have contrasting width and birefringence, the inner cycle being distinctly bright and narrow, the outer being broad and dark. The central area is usually slightly broader than the shield width.
The width contrast between the two rim cycles is greater than that seen in other tubodiscids. The shield morphology and LM appearance are similar to Sollasites coccoliths, but no central area structures have been observed.
Size: 5.5-6.5 µm
Tags | LITHS: placolith, elliptical, CA: vacant, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent, |
Metrics | Lith size: 5->7µm; Data source notes: original description +/-0.5 µm |
Geological Range:
Last occurrence (top): within NC4 zone (132.87-132.93Ma, top in Hauterivian stage). Data source: Bown 2005
First occurrence (base): within NC2 zone (139.45-144.93Ma, base in Berriasian stage). Data source: Bown 2005
Plot of occurrence data:
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Tubodiscus frankiae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 27-1-2021
Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=11275 Go to Archive.is to create a permanent copy of this page - citation notes |