Micrantholithus


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

Distinguishing features: Pentaliths with triangular segments and sutures that go to angles of the pentagon.


Daughter taxa: (blue => in age window 0-800Ma)
Micrantholithus with crenulated outline due to two shallow indentations in each segment.
Micrantholithus with pentagonal outline.

Micrantholithus with stellate outline due to shallow indentations in each segment.
Micrantholithus with shallow indentations in each segment.
Micrantholithus with crenulated outline due to two indentations in each segment.
Very large (14–25 µm) with deeply indented sides, and so medium to long free rays (as long as or slightly longer than the central body radius).
Medium sized (<7µm) stellate Micrantholithus, i.e. segments with concave sides.
Specimens not identified to species level

Taxonomy:

Citation: Micrantholithus Deflandre in Deflandre & Fert, 1954
Rank: Genus
Type species: Micrantholithus flos Deflandre, 1950; holotype designated by Deflandre in Deflandre and Fert (1954).

Farinacci & Howe catalog pages: Micrantholithus *

Distinguishing features: Pentaliths with triangular segments and sutures that go to angles of the pentagon.


Morphology remarks: Pentaliths of this genus are readily distinguishable from Braarudosphaera, in which the sutures bisect the edges of the pentalith. The Mesozoic forms are stratigraphically separated from the morphologically identical Tertiary Micrantholithus group, by around 35 million years. However, the earliest braarudosphaerids are exclusively Micrantholithus types and these Lower Cretaceous morphologies are found consistently from Berriasian-Aptian, after which they are largely replaced by Braarudosphaera morphologies. An Upper Cretaceous (Coniacian) Micrantholithus species, M. quasihoschulzii, has been described by Burnett (1998), but they are not found consistently again until the lowermost Paleocene, where they co-occur with Braarudosphaera.

Geological Range:
Last occurrence (top): near top of Coniacian Stage (93% up, 86.5Ma, in Coniacian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Berriasian Stage (0% up, 145Ma, in Berriasian 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

Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 132-199. 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


nannotaxlogo400px

Micrantholithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 18-9-2019

Taxon Search:
Advanced Search

Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10655 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (0)

No comments yet. Be the first!

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics