Braarudosphaerales


Classification: Mesozoic -> Braarudosphaerales
Sister taxa: Arkhangelskiales, Eiffellithales, Stephanolithiales, Podorhabdales, Watznaueriales, Syracosphaerales, Heterococcoliths inc sedis, Holococcoliths, Braarudosphaerales, Nannoliths inc sedis, Mesozoic non–coccoliths, hidden,

Distinguishing features: Nannoliths formed of multiple layers of thin elements, arranged with rotational symmetry, and showing tangential c-axis orientations.


Daughter taxa: (blue => in age window 0-800Ma) Granddaughter taxa
Families included by Lees & Bown 2016
Nannoliths constructed from 5 (rarely 6) segments which form a pentalith (a five-sided plate); C-axes tangential to pentalith outline in plan view; individual crystal units show laminar ultrastructure.

Conical, globular or cylindrical nannoliths composed of plates spirally-arranged around an axial cavity or canal. Plate c-axes are arranged tangentially to the longitudinal axis.

Other groups tentatively included here
Nannoliths composed of two superposed wall cycles and a central-area which may be closed, open and vacant, or spanned by a diaphragm-like structure. Elements have tangential c-axis orientation.

Genera incertae sedis with radial structure and tangential c-axis orientation

Taxonomy:

Citation: Braarudosphaerales Aubry 2013 emend Lees & Bown 2016
Rank: Order
Notes & discussion: Lees & Bown (2016) emended the order Braarudosphaerales to include the Nannoconaceae on the grounds that pentaliths and nannoconids both showed structures formed of multiple layers of thin elements. In the case of pentaliths these thin elements appear as laminae witin individual crystal units, in nannoconids they are stacked with offset, both groups appear at the end Jurassic and show tangential c-axis orientations as well as simple rotational symmetry, (without modification by central area structures or elongation into elliptical forms). 
Varol & Bowman (2019) have since shown that Polycyclolithus is a nannoconid, from side view observations with a mobile mount.
Other possibly related taxa which show tangential c-axes and simple rotational symettry but not stacked layers of elements include the Polycyclolithaceae and the genera Kokia, and Tegulalithus. These are now tentively included here.

Farinacci & Howe catalog pages: Braarudosphaerales [no catalog entry yet]

Distinguishing features: Nannoliths formed of multiple layers of thin elements, arranged with rotational symmetry, and showing tangential c-axis orientations.


Morphology remarks: To determine if c-axes are tangential (as in this group) as opposed to radial (as in the R-units that form the bright part of most heterococccoliths)  nannofossils should be observed in cross-polarised light with a gypsum (1λ) plate or other accesory plate (see e.g. Moshkovitz & Osmond 1989).

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): near top of Oxfordian Stage (89% up, 157.9Ma, in Oxfordian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Aubry, M. -P. (2013). Cenozoic Coccolithophores: Braarudosphaerales. Micropaleontology Press, American Museum of Natural History, New York. 336-. gs

Lees, J. A. & Bown, P. R. (2016). New and intriguing calcareous nannofossils from the Turonian (Upper Cretaceous) of Tanzania. Journal of Nannoplankton Research. 36(1): 83-95. gs

Moshkovitz, S. & Osmond, K. (1989). The optical properties and microcrystallography of Arkhangelskiellaceae and some other calcareous nannofossils of the Late Cretaceous. In, Crux, J. A. & Heck, S. E. v. (eds) Nannofossils and their applications. Ellis Horwood, Chichester 76-97. 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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Braarudosphaerales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-10-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10114 Go to Archive.is to create a permanent copy of this page - citation notes



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