Pemma Pentaliths with a central depression/perforation in each segment; often producing elevated, robust structures that are commonly observed in side view.
Citation: Braarudosphaeraceae Deflandre, 1947Rank: FamilyTaxonomic 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: Parent taxon (Braarudosphaerales): 2N(?) cell covered by pentaliths (plates formed of 5 segments with lamellar sub-structure) formed extracellualrly
N: cell motile, covered by scales This taxon: 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. Size:
Ecology & Biogeography: Predominantly neritic both at the present day and in the fossil record.
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Lith size: 2->30µm; Segments: 5->5;
The morphological data given here can be used on the advanced search page. See also these notes
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 Albian stage). Data source: Total of range of species in this database
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: this is a higher taxon page so Neptune data is not plotted. For the customisable plot option go to a genus page Parent: Braarudosphaerales
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. gsO
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. gsVO
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-. gsVO
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. gsVO
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
Braarudosphaeraceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 24-5-2022
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