Tubodiscus


Classification: Mesozoic -> Podorhabdales -> Tubodiscaceae -> Tubodiscus
Sister taxa: Manivitella, Tubodiscus,

Short diagnosis: Tubodiscids with high and birefringent proximal collar cycle and wide central-area. Rim image is clearly bicyclic in XPL.


Daughter taxa (blue => in age window 0-300Ma)
Medium sized Tubodiscus with narrow shields and wide, open, central area. The rim image is bicyclic XPL and the two cycles have contrasting birefringence, the inner cycle being distinctly bright. The inner cycle is usually slightly narrower than the outer.
A large (c. 7.5 ┬Ám), typically broadly elliptical species of Tubodiscus with two distinct rim cycles, the outermost cycle is dark and often slightly broader, the inner cycle displays white interference colours; the central area is broad (usually greater than the width of the rim) and no central structures have been observed.
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.
Large Tubodiscus with wide central area and birefringent collar cycle (white).
Tubodiscus with broad, high collar cycle that is highly birefringent (yellow-orange) in XPL, and the coccoliths are often seen in side view.
Specimens not identified to species level

Taxonomy:

Citation: Tubodiscus Thierstein, 1973
Rank: Genus
Type species: Tubodiscus verenae Thierstein, 1973.

Farinacci & Howe catalog pages: Tubodiscus *

Short diagnosis: Tubodiscids with high and birefringent proximal collar cycle and wide central-area. Rim image is clearly bicyclic in XPL.

Geological Range:
Last occurrence (top): within Albian Stage (100.50-112.95Ma, top in Albian stage). Data source: Total of range of species in this database
First occurrence (base): within Berriasian Stage (139.39-145.01Ma, base in Berriasian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R.; Rutledge, D.C.; Crux, J.A. & Gallagher, L.T., (1998). Early Cretaceous. In: Bown, P.R. (Editor), Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. Chapman & Hall, pp. 86-131.

Thierstein, H.R., (1973). Lower cretaceous calcareous nannoplankton biostratigraphy. Abhandlungen der Geologischen Bundesanstalt, 29: 3-52.


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Tubodiscus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-1-2018

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