R. bisecta group

Classification: Coccolithophores -> Isochrysidales -> Noelaerhabdaceae -> Reticulofenestra -> R. bisecta group
Sister taxa: C. floridanus group, R. bisecta group, R. lockeri group, R. parvula group, R. pseudoumbilicus group, R. reticulata group, R. umbilicus group, R. sp.,

Daughter taxa: (blue => in age window 0-800Ma)
Paleogene species
Medium to large (~5-10 µm) with a solid central plug.
Medium to large; very narrow central opening with weakly birefringent net.
Large to very large (>10 µm) with a solid central plug.
Large, with thickened, dome-like distal shield; central area filled by a plug.
Neogene (high latitude) species
Medium sized (5-8µm) with closed central area
Small (<5µm) with closed central area


Citation: R. bisecta group
Rank: species group
Notes & discussion: This group broadly, but not completely, correlates with the general usage of the genus Dictyococcites Black, 1967. That is, any workers who use the genus Dictyococcites will place these species in the genus, but they may also include varying numbers of other species, with closed or nearly closed central areas. The type species of Dictyococcites does not however belong to this group so the name should not be applied to applicable. Moreover some workers apply the name Dictyococcites to any elliptical reticulofenstrids with a closed central area. This is a polyphyletic grouping and so is not acceptable.

Distinguishing features: Elliptical reticulofenestrids, central area closed by very robust, conspicuous distal ‘plug’ (birefringent).

Farinacci & Howe catalog pages:

Search data:
TagsCA: Placoliths: closed-----,
CSPH: spherical, V-UNITS: none, R-UNITS: all, c-str, distal shield, prox shield, tube, DETAILS: isogyres kinked, isogyres oblique,
MetricsLith size: 3->16µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: As defined this group is essentially restricted to the Paleogene.
Last occurrence (top): at top of Early Pleistocene Sub-Epoch (100% up, 0.8Ma, in Calabrian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Lutetian Stage (23% up, 46.3Ma, in Lutetian stage). Data source: Total of range of species in this database

Plot of occurrence data:


Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs :: view :: open


R. bisecta group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 14-7-2020

Taxon Search:
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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=1146 Go to Archive.is to create a permanent copy of this page - citation notes

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