Calculites


Classification: Mesozoic -> Holococcoliths -> Common genera -> Calculites
Sister taxa: Calculites, Lucianorhabdus, Orastrum, Owenia,

Distinguishing features: Holococcoliths with a proximal plate of four blocks; ridged and pitted distal surface; and short, narrow, hollow spines. Entire coccolith bright in xpl in plan view


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

Calculites with four blocks divided along diagonal sutures that bend sharply where they meet the rim. The transverse and longitundinal blocks are in opposing crystallographic orientation.
Sutures nearly aligned with the axes of the ellipse, low birefringence. May have a stem.

Calculites with a single, relatively wide, central perforiation 
Small Calculites with short, hollow central stem and small basal plate with one to seven pores.
Small (holotype 3.3 µm), with wide central plate with multiple perforations.
Medium sized (holotype 5.3 µm) with a small central perforation and kinked isogyres.
Calculites with four blocks divided along broadly diagonal sutures.
Calculites with four blocks divided along near axial sutures.
Very small (holotype 2.6 µm) Calculites with a long, narrow, central perforation
Small Calculites with four blocks divided along near axial sutures (extinction lines) at 0˚ and diagonal sutures (extinction lines) at 45˚ to the polarising directions.
Small (holotype 4µm) species with a long, narrow central perforation ddd
Formed of 4 blocks like C. obscurus, but with a perforation in each block, and blocks go into extinction separately
Like C. turonicus, but larger, with a slighlty thickened (brighter) rim and simpler sutures.
Early Cretaceous species

Small holococcoliths with a rim, and central-area plate divided by a distinct, longitudinal suture.
Specimens not identified to species level

Taxonomy:

Citation: Calculites Prins & Sissingh in Sissingh, 1977
Rank: Genus
Type species: Calculites obscurus (Deflandre, 1959) Prins & Sissingh in Sissingh, 1977

Farinacci & Howe catalog pages: Calculites *

Distinguishing features: Holococcoliths with a proximal plate of four blocks; ridged and pitted distal surface; and short, narrow, hollow spines. Entire coccolith bright in xpl in plan view

Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Maastrichtian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Hauterivian Stage (0% up, 133.9Ma, in Hauterivian 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

Sissingh, W. (1977). Biostratigraphy of Cretaceous calcareous nannoplankton. Geologie en Mijnbouw. 65(1): 37-65. gs


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Calculites compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-10-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10163 Go to Archive.is to create a permanent copy of this page - citation notes



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