Nannotax3 - ntax_cenozoic - Braarudosphaeraceae

Citation: Braarudosphaeraceae Deflandre, 1947

Taxonomic discussion: Only two extant species have been described and only one of these, B. bigelowii, is well-established, but the family has a geological record back to the Early Cretaceous including several genera and many species (e.g. Perch-Nielsen 1985a,b, Aubry 1989, Bown 2005). These include forms with heavily ornamented pentaliths and pentaliths with concave sides. They sometimes occur in enormous abundance in sediments suggesting that Braarudosphaera can form massive blooms (Peleo-Alampay et al. 1999). Braarudosphaera layers are particularly well known in the Oligocene in the Atlantic (Peleo-Alampay et al. 1999, Kelly et al. 2003, Liebrand et al. 2017). At present day, Braarudosphaera occurs sporadically in shelf environments, usually under conditions of lowered salinity.
Affinities: Braarudosphaera was long considered a group of highly uncertain affinities and possibly dinoflagellates, but recent molecular genetic data (Takano et al. 2006) has shown that they occupy a basal position within the coccolithophore clade, and so are definitely haptophytes and probably derived in some way from coccolithophores.

Distinguishing features: Coccospheres pentagonal dodecahedra formed of five pentagonal plates

Morphology: Basic morphology: Cell is typically non-motile and entirely enclosed in an exotheca of twelve plates each with five-fold symmetry (pentaliths). Cells have frequently been isolated but have never grown in culture, they contain visible chloroplasts, so are not cysts or protozoa (Lefort 1972, pers. comms. Green, Probert, Hagino). Lefort (1972) observed, and illustrated, rare specimens of B. magnei with two apically placed, sub-equal flagella.
Pentalith morphology: Pentaliths consist of five segments, each of which behaves as a discrete crystal-unit with c-axis parallel to edge of the pentalith. A lamellar substructure to the segments is consistently present.

Ecology & Biogeography: Predominantly neritic both at the present day and in the fossil record.

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at base of Cenomanian Stage (0% up, 100.5Ma, in Cenomanian stage). Data source: Total of range of species in this database

References:

Aubry, M. -P. (1989a). Handbook of Cenozoic calcareous nannoplankton. Book 3: Ortholithae (Pentaliths, and others), Heliotithae (Fasciculiths, Sphenoliths and others). Micropaleontology Press, American Museum of Natural History, New York. 1-279. gs

Bown, P. R. (2005d). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research. 27(1): 21-95. gs V O

Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Early Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gs

Deflandre, G. (1947a). Braarudosphaera nov. gen., type d'une famille nouvelle de Coccolithophorides actuels a elements composites. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences, Paris. 225: 439-441. gs V O

Kelly, D. C., Norris, R. D. & Zachos, J. C. (2003). Deciphering the paleoceanographic signi¢cance of Early Oligocene Braarudosphaera chalks in the South Atlantic. Marine Micropaleontology. 49: 49-63. gs

Lefort, F. (1972). Quelques caracteres morphologiques de deux especes actuelles de Braarudosphaera (Chrysophycees, Coccolithophoracees). Botaniste. 20(3): 13-. gs V O

Liebrand, D. et al. (2018). Orbitally forced hyperstratification of the Oligocene South Atlantic Ocean. Paleoceanography and Paleoclimatology. 33: 511-529. gs

Peleo-Alampay, A. M., Mead, G. A. & Wei, W. (1999). Unusual Oligocene Braarudosphaera-rich layers of the South Atlantic and their palaeoceanograpghic implications. Journal of Nannoplankton Research. 21(1): 17-26. gs V O

Perch-Nielsen, K. (1985a). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 427-555. gs

Perch-Nielsen, K. (1985b). Mesozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 329-426. gs

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

Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	Braarudosphaera Pentaliths approximately pentagonal, sutures go to edges of pentagon.	B. bigelowii B. insecta B. magnei B. pentagonica B. perampla B. perversus B. sequela B. stylifera B. sp.
	Hexadelus Thin nannoliths similar to Braarudosphaera but with 6 segments - usually occur as isolated segments	H. archus
	Micrantholithus Pentaliths with sutures emerging through corners; edge often indented giving stellate outline	M. breviradiatus M. disculus M. flos M. astrum M. entaster M. excelsus M. hebecuspis M. minimus M. pinguis M. vesper M. attenuatus M. mirabilis M. angulosus M. bramlettei M. bulbosus M. crenulatus M. tinus M. sp.
	Pemma Pentaliths with a central depression/perforation in each segment; often producing elevated, robust structures that are commonly observed in side view.	P. basquense P. bybelliae P. papillatum P. rotundum P. stradneri P. triquetra P. uncinata P. sp.
	Pentaster	P. lisbonensis

Tags	LITHS:
Metrics	Lith size: 2->30µm; Segments: 5->5;

Braarudosphaeraceae

References:

Comments (0)

Add Comment