Distinguishing features: Nannoliths formed of multiple layers of thin elements, arranged with rotational symmetry, and showing tangential c-axis orientations.
Daughter taxa (time control age-window is: 0-800Ma)![]() | Granddaughter taxa | ||||
Families included by Lees & Bown 2016 | |||||
![]() | ![]() | Braarudosphaeraceae 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. | |||
![]() | ![]() | ![]() | Transitional genera Nannoliths intermediate between Nannoconacaea and Braarudosphaeraceae | ||
Nannoconaceae 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 | |||||
![]() | Polycyclolithaceae 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. | ||||
![]() | ![]() | ![]() | Other nannoliths with tangential c-axes Genera incertae sedis with radial structure and tangential c-axis orientation |
Taxonomy:
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: 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).
Tags | LITHS: nannolith-radiate, pentagonal, |
Metrics | Lith size: 0->0µm; Segments: 5->5; |
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:
Aubry, M. -P. (2013). Cenozoic Coccolithophores: Braarudosphaerales. Micropaleontology Press, American Museum of Natural History, New York. 1-336. 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 V O 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. & van Heck, S. E. (eds) Nannofossils and their applications: Proceedings of the 2nd INA Conference, London 1987. British Micropalaeontological Society Publication Series. 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. gsReferences:
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Braarudosphaerales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-4-2021
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10114 Go to Archive.is to create a permanent copy of this page - citation notes |