Calculites turonicus

Classification: Mesozoic -> Holococcoliths -> Common genera -> Calculites -> Calculites turonicus
Sister taxa: C. favosus, C. anfractus, C. axosuturalis, C. obscurus, C. ovalis, C. rosalyniae, C. additus, C. cenomanicus, C. cyclops, C. juliae, C. maghredaswampensis, C. paulus, C. percernis, C. proscissus, C. turonicus, C. sarstedtensis, C. suturus, C. sp.,

Distinguishing features: Small with very small central perforation


Citation: Calculites turonicus Lees, 2007
Rank: Species

Farinacci & Howe catalog pages: Calculites turonicus *

Distinguishing features: Small with very small central perforation

Morphology remarks: "A small species of Calculites which bears a very small central perforation and in which the central part is slightly darker in XPL than the outer part (there is no discernable rim). At 0 ̊ in XPL, the extinction lines are aligned with the polarising directions and bifurcate (indicating a rim block in extinction?) at each end of the lith. The central perforation is not obvious in this direction, where the extinction lines meet. On rotation, the extinction lines form v-shapes that do not join in the centre of the lith. The small perforation is then clear.
Differentiation: The new species bears a resemblance to C. percernis (see Pl.10, figs 46-53), but the latter is generally smaller and the central area is not slightly darker than the rim. The extinction lines of C. percernis are also different, with the short axis line being kinked, so as to appear offset, rather than straight, as in the new species." [Lees 2007]

Size: Holotype dimensions: L = 3.96μm, W = 2.86μm.

Search data:
TagsLITHS: holococcolith, elliptical, R-UNITS: R-prominent, DETAILS: ca_disjunct, rim-unicyclic,
MetricsLith size: 3->4µm;
Sources: original description
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within Early Turonian Substage (92.90-93.90Ma, top in Turonian stage). Data source: Lees 2007 (original description)
First occurrence (base): within Early Turonian Substage (92.90-93.90Ma, base in Turonian stage). Data source: Lees 2007 (original description)

Plot of occurrence data:

  • (NB There is no histogram as there are no occurrence records for the taxon in the Neptune database) Parent: Calculites


    Lees, J. A. (2007). New and rarely reported calcareous nannofossils from the Late Cretaceous of coastal Tanzania: outcrop samples and Tanzania Drilling Project Sites 5, 9 and 15. Journal of Nannoplankton Research. 29(1): 39-65. gs :: view :: open


    Calculites turonicus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 2-7-2020

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    Short stable page link: Go to to create a permanent copy of this page - citation notes

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