Braarudosphaera


Classification: Mesozoic -> Braarudosphaerales -> Braarudosphaeraceae -> Braarudosphaera
Sister taxa: Braarudosphaera, Bukryaster, Hexalithus, Micrantholithus, Trapezopentus,

Distinguishing features: Pentaliths with trapezoidal segments and sutures that go to edges of the pentagon.


Daughter taxa: (blue => in age window 0-800Ma)

Braarudosphaera with 5-sided segments; outer tips of segments truncated tangentially


Braarudosphaera with one segment bearing a ridge which extends into a protruding spine
Braarudosphaera with pentagonal outline.
One segment asymetrically enlarged.
Pentaliths with the segments overlapping each other clockwise, tips tilted distally
Very small (<2µm), rounded, Braarudosphaera
B. africana group - Albian
Stellate Braarudosphaera with long, relatively narrow rays due to deep indentations where the sutures meet the lith edge.
Braarudosphaera with stellate outline due to diamond-shaped segments and therefore indentations where the sutures meet the lith edge.
Braarudosphaera with very shallow indentations where the sutures meet the lith edge.
Braarudosphaera with rounded tips to the segments
Braarudosphaera with pentagonal outline and bilateral symmetry, i.e. the sutures bisect the edges.
Braarudosphaera with sutural ridges on the pentaliths
Specimens not identified to species level

Taxonomy:

Citation: Braarudosphaera Deflandre, 1947
Rank: Genus
Type species: Pontosphaera bigelowii Gran and Braarud, 1935
Notes & discussion: A range of Braarudosphaera species have been decribed from the Albian, notably by Black (1973) and Hill (1976). Lambert (1986) showed that all these forms were probably conspecific, being derived from a variable species which could produce very elevated pantaltihs which disintegrate into different shaped layers. He considered B. africana the senior synonym for this species.
In the table above the morhotypes are arranged in sequence as deduced by Lambert (1986) - ie. from forms produced at the tip of the cones to those at the base. 

Farinacci & Howe catalog pages: Braarudosphaera * , ,

Distinguishing features: Pentaliths with trapezoidal segments and sutures that go to edges of the pentagon.

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at base of Aptian Stage (0% up, 126.3Ma, in Aptian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Black, M. (1973). British Lower Cretaceous Coccoliths. I-Gault Clay (Part 2). Palaeontographical Society Monograph. 127: 49-112. gs

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

Hill, M. E. (1976). Lower Cretaceous calcareous nannofossils from Texas and Oklahoma. Palaeontographica Abteilung B. 156: 103-179. gs

Lambert, B. (1986). La notion d'espèce chez le genre Braarudosphaera Deflandre, 1947: mythe et réalité. Revue de Micropaleontologie. 28(4): 255-264. gs


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Braarudosphaera compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 24-7-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10099 Go to Archive.is to create a permanent copy of this page - citation notes



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