Nannotax3 - ntax_cenozoic - Micrantholithus

Micrantholithus


Classification: ntax_cenozoic -> Braarudosphaerales -> Braarudosphaeraceae -> Micrantholithus
Sister taxa: Braarudosphaera, Hexadelus, Micrantholithus, Pemma, Pentaster

Daughter taxa (time control age-window is: 0-800Ma)
sides convex to weakly indented
Micrantholithus breviradiatus
Small to large Micrantholithus with shallowly indented sides and rounded apices.
Micrantholithus disculus
Simple, elevated Micrantholithus with rounded outline and elliptical side views.
Micrantholithus flos
Micrantholithus with relatively straight edges, sutures often raised
sides deeply indented
Micrantholithus astrum
Medium sized Micrantholithus with deeply indented sides and rounded apices.
Micrantholithus entaster
Medium sized Micrantholithus with deeply indented sides and elevated central star
Micrantholithus excelsus
Large, elevated Micrantholithus with deeply indented sides and gracile, long rays. The height of the pentalith results in a ragged LM appearance.
Micrantholithus hebecuspis
Large Micrantholithus with deeply indented sides and blunt, flat-ended apices.
Micrantholithus minimus
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 pinguis
Medium sized Micrantholithus with deeply indented sides and elevated structure.
Micrantholithus vesper
Stellate Micrantholithus with deeply indented sides
very deeply indented sides
Micrantholithus attenuatus
Stellate Micrantholithus with deeply indented sides and gracile, long rays.
Micrantholithus mirabilis
Micrantholithus with thickened central area and long extensions formed typically by single segments.
ornate species
Micrantholithus angulosus
Arms end in a trilobate termination. most specimens thin with narrow arms.
Micrantholithus bramlettei
Stellate pentalith with pointed rays and double indented sides.
Micrantholithus bulbosus
Micrantholithus with relatively straight edges and raised ridges around the sutures that widen at their ends.
Micrantholithus crenulatus
Micrantholithus with crenulate edges.
Micrantholithus tinus
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.
Micrantholithus sp.
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

Taxonomic discussion:
Initially invalidly described in Deflandre 1950, subsequently validated in Deflandre & Fert 1954.

Distinguishing features:
Parent taxon (Braarudosphaeraceae): Coccospheres pentagonal dodecahedra formed of five pentagonal plates
This taxon: Pentaliths with sutures emerging through corners; edge often indented giving stellate outline

Farinacci & Howe catalog pages: Micrantholithus * , Citrocalculus *


Morphology: 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, CA: process,
MetricsLith size: 3->30µm; Segments: 5->5; Liths per sphere: 12->12
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): at top of Burdigalian Stage (100% up, 16Ma, in Burdigalian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Danian Stage (0% up, 66Ma, 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. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gs

Deflandre, G. & Fert, C. (1954). Observations sur les coccolithophoridés actuels et fossiles en microscopie ordinaire et électronique. Annales de Paléontologie. 40: 115-176. gs

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. gs


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Micrantholithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 25-9-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=855 Go to Archive.is to create a permanent copy of this page - citation notes



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