Micrantholithus


Ancestry: Coccolithophores -> Braarudosphaerales -> Braarudosphaeraceae -> Micrantholithus
Sister taxa: Braarudosphaera, Hexadelus, Micrantholithus, Pemma, Pentaster,

Short diagnosis: Pentaliths with sutures emerging through corners; edge often indented giving stellate outline


Daughter taxa (blue => in age window 0-300Ma)
Arms end in a trilobate termination. most specimens thin with narrow arms.
Medium sized Micrantholithus with deeply indented sides and rounded apices.
Stellate Micrantholithus with deeply indented sides and gracile, long rays.
Stellate pentalith with pointed rays and double indented sides.
Small to large Micrantholithus with shallowly indented sides and rounded apices.
Micrantholithus with relatively straight edges and raised ridges around the sutures that widen at their ends.
Micrantholithus with crenulate edges.
Simple, elevated Micrantholithus with rounded outline and elliptical side views.
Medium sized Micrantholithus with deeply indented sides and elevated central star
Large, elevated Micrantholithus with deeply indented sides and gracile, long rays. The height of the pentalith results in a ragged LM appearance.
Micrantholithus with relatively straight edges, sutures often raised
Large Micrantholithus with deeply indented sides and blunt, flat-ended apices.
A small (typically <4 µm) Micrantholithus with raised ridges along the line of the segment sutures that give the appearance of a deeply indented pentalith. Many specimens, however, have thin calcite between the raised, birefringent areas.
Micrantholithus with thickened central area and long extensions formed typically by single segments.
Medium sized Micrantholithus with deeply indented sides and elevated structure.
Micrantholithus with bifurcate ray-like extension from each segment (sutures do not go along arms). Resembles a discoaster but evidently shows the birefringence of a pentalith and a specimen of M. concinnus with short rays is illustrated from the same sample so the identification seems well-founded.
Stellate Micrantholithus with deeply indented sides
Specimens which cannot be assigned to established species

Taxonomy:

Citation: Micrantholithus Deflandre in Deflandre & Fert 1954
Rank: Genus
Type species: Micrantholithus flos Deflandre in Deflandre & Fert 1954
Variants: Citrocalculus - barrel-shaped in profile
Notes & discussion: Initially invalidly described in Deflandre 1950, subsequently validated in Deflandre & Fert 1954.

Farinacci & Howe catalog pages: Citrocalculus * Micrantholithus *

Short diagnosis: Pentaliths with sutures emerging through corners; edge often indented giving stellate outline


Morphology remarks: Similar to Braarudosphaera but sutures emerge through corners of pentalith and edge often indented.

Ecology & Biogeography: Predominantly a shelf taxon

Search data:
TagsLITHS: nannolith-radiate, pentagonal,
CSPH: not known, T-UNITS: all,
MetricsLith size: 3->30µm; Segments: 5->5; Liths per sphere: 12->12
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: Predominantly Palaeogene but most of the common species have been sporadically recorded in the Miocene
Last occurrence (top): within Burdigalian Stage (15.97-20.44Ma, top in Burdigalian stage). Data source: Total of range of species in this database
First occurrence (base): within Danian Stage (61.61-66.04Ma, base in Danian 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. & Fert, C., (1954). Observations sur les coccolithophoridés actuels et fossiles en microscopie ordinaire et électronique. Annales de Paléontologie, 40: 115-176.

Deflandre, G., (1950). Observations sur les Coccolithophoridés, à propos d'un nouveau type de Braarudosphaeridé, Micrantholithus, à éléments clastiques. Comptes Rendus (Hebdomadaires des Séances) de l'Académie des Sciences Paris, 231: 1156-1158.


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Micrantholithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-10-2017

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AphiaID: 604301 Nomenclatural data on WoRMS
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