Nannotax3 - ntax_main - Braarudosphaerales

Citation: Braarudosphaerales Aubry 2013

Taxonomic discussion: Recent research has demonstrated that modern Braarudosphaera produces the pentaliths in-situ at the cell margin rather than in a coccolith vesicle, and that they have a very different structure to heterococcoliths, characterised by laminar sub-structure and tangential c-axis orientations (Hagino et al. 2016). So, they are clearly produced by a different biomineralisation mode (sensu Young et al. 1999) to either holococcoliths or heterococcoliths. In parallel, molecular genetic data shows they are haptophytes closely related to coccolithophores but either occupying a basal position within the coccolithophore clade or falling just outside it (Takano et al. 2006, Hagino et al. 2013). These two lines of evidence strongly justify separating the group as a discrete order within the haptophyta.
In the Cenozoic the order only contains the one, well-established, family, the Braarudosphaeraceae. However, in the Mesozoic there are other groups showing affinities to them - in particular the Nannoconids (Lees & Bown 2016).

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.

Distinguishing features:
Parent taxon (ntax_main):
This taxon: 2N(?) cell covered by nannoliths with lamellar sub-structure and tangential C-axes. N: cell motile, covered by scales

A key feature of this group is that the nannoliths are formed of plates with tangelntial c-axes. 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 ranges of the species in this database
First occurrence (base): within NJ15b subzone (149.47-156.78Ma, base in Oxfordian stage). Data source: Total of ranges of species in this database

References:

Aubry, M. -P. (2013). Cenozoic Coccolithophores: Braarudosphaerales. Micropaleontology Press, American Museum of Natural History, New York. 1-336. gs

Hagino, K., Onuma, R., Kawachi, M. & Horiguchi, T. (2013). Discovery of an Endosymbiotic Nitrogen-Fixing Cyanobacterium UCYN-A in Braarudosphaera bigelowii (Prymnesiophyceae). PLoS One. 8(12): 1-11. gs

Hagino, K., Tomioka, N., Young, J. R., Takano, Y., Onuma, R. & Horiguchi, T. (2016). Extracellular calcification of Braarudosphaera bigelowii deduced from electron microscopic observations of cell surface structure and elemental composition of pentaliths. Marine Micropaleontology. 125(1): 85-94. 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. & 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 O

Takano, Y., Hagino, K., Tanaka, Y., Horiguchi, T. & Okada, H. (2006). Phylogenetic affinities of an enigmatic nannoplankton, Braarudosphaera bigelowii based on the SSU rDNA sequences. Marine Micropaleontology. 60: 145-156. 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

Young, J. R., Davis, S. A., Bown, P. R. & Mann, S. (1999). Coccolith ultrastructure and biomineralisation. Journal of Structural Biology. 126: 195-215. gs

Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	Braarudosphaeraceae Coccospheres pentagonal dodecahedra formed of five pentagonal plates	Braarudosphaera Micrantholithus Hexadelus Pemma Pentaster Bukryaster Trapezopentus
	Transitional genera Nannoliths intermediate between Nannoconacaea and Braarudosphaeraceae	Hexalithus Polycostella
	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.	Faviconus Nannoconus
	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.	Eprolithus Radiolithus Farhania Lithastrinus Uniplanarius Quadrum Micula Palaeomicula
	Other nannoliths with tangential c-axes Genera incertae sedis with radial structure and tangential c-axis orientation	Kokia Tegulalithus

Braarudosphaerales

References:

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