Braarudosphaeraceae


Classification: Mesozoic -> Braarudosphaerales -> Braarudosphaeraceae
Sister taxa: Braarudosphaeraceae, Nannoconaceae,

Short diagnosis: 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.


Daughter taxa (blue => in age window 0-300Ma) Granddaughter taxa
Nannoliths constructed from five segments which form a pentalith (a five-sided plate), although different outlines (e.g. stellate, subcircular) are also common in the fossil record. The segments are trapezoidal and the sutures go to edges of the pentagon.

Pentaliths with long spines protuding from the points.

Six-rayed, stellate to hexagonal nannoliths formed from six elements.

Nannoliths constructed from five segments which form a pentalith (a five-sided plate), although different outlines (e.g. stellate, subcircular) are also common in the fossil record. In Micrantholithus the segments are triangular, and the sutures go to points of the pentagon.

Pentalith constructed of overlapping trapezoidal elements surrounding a large central opening.

Taxonomy:

Citation: Braarudosphaeraceae Deflandre, 1947
Rank: Family

Farinacci & Howe catalog pages: Braarudosphaeraceae [no catalog entry yet]

Short diagnosis: 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.


Morphology remarks: Fossil lith types show considerable diversty, including very tall and heavily calcified forms and forms with stellate outlines. The extant Braarudosphaera bigelowii has a cell-wall covering of twelve pentaliths, which form an imperforate dodecahedron. Two main morphotypes are seen through much of the evolutionary history: Braarudosphaera in which the sutures between segments go to edges of the pentagon and Micrantholithus in which the sutures go to the points of the pentagon. The two styles may form distinct taxa but in some cases single liths may change from the Braarudosphaera- to Micrantholithus- style up (or down) through the laminations (e.g., Lambert, 1986).

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): within Tithonian Stage (145.01-152.06Ma, base in Tithonian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R.; Rutledge, D.C.; Crux, J.A. & Gallagher, L.T., (1998). Early Cretaceous. In: Bown, P.R. (Editor), Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. Chapman & Hall, pp. 86-131.

Deflandre, G., (1947). 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.

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


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Braarudosphaeraceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-12-2017

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