Nannotax3 - ntax_cenozoic - Zygodiscus Nannotax3 - ntax_cenozoic - Zygodiscus


Classification: ntax_cenozoic -> Zygodiscales -> Zygodiscaceae -> Zygodiscus
Sister taxa: Lophodolithus, Neochiastozygus, Zygodiscus ⟩⟨ Chiphragmalithus, Isthmolithus, Neococcolithes, Nannotetrina

Daughter taxa (time control age-window is: 0-800Ma)
Zygodiscus adamas
Zygodiscus with “lozenge-shaped” bar.
Zygodiscus cearae
Large (11.0-13.5 µm) murolith coccolith with a broad central-area spanned by a transverse bar made up of crystallographically distinct units that appear as low-angle diagonal cross-bars at certain orientations in XPL.
Zygodiscus clausus
Medium sized elliptical murolith comprising an unadorned plate with a central hole spanned and filled by a disjunct bar. The precise crystallographic orientation of the bar appears to vary.
Zygodiscus herlyni

Zygodiscus multiforus
Medium- to large-sized elliptical murolith with a relatively broad, birefringent rim that has a perforate appearance on one side. The central-area is spanned by a transverse bar.
Zygodiscus plectopons
Murolith with wide central area spanned by a parallel side bar.
Zygodiscus sheldoniae
Medium to large sized murolith with a broad plate enclosing a small disjunct bar.
Zygodiscus sp.
Specimens which cannot be assigned to any established species


Citation: Zygodiscus Bramlette and Sullivan, 1961
taxonomic rank: Genus
Type species: Zygodiscus adamas Bramlette & Sullivan, 1961

Distinguishing features:
Parent taxon (Zygodiscaceae): Muroliths with rim formed from well-developed V- and variably developed R-units, with opposite imbrication directions, and central area structures that include disjunct transverse bars and diagonal crosses. R-units vestigial or not observed in several genera (Chiphragmalithus, Isthmolithus, Neococcolithes).
This taxon: Muroliths with well-developed V- and R-units and transverse bar in central-area. LM image is dominated by bright, broad R-unit inner cycle; V-unit cycle is narrow.

Farinacci & Howe catalog pages: Zygodiscus + + *

Coccolith medium to large size (5-14 µm), no great size variation between species.

Search data:
LITHS: murolith, elliptical, CA: ca_disjunct, bar, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent,
Lith size: 5->14µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: The decribed species are not well-differentitated and all appear to have similar ranges, predominantly occurring in the Late Paleocene (NP6 to NP9) but extending into the Early Eocene (NP10-11).
Last occurrence (top): at top of NP11 zone (100% up, 53.7Ma, in Ypresian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NP6 zone (58.97-59.54Ma, base in Selandian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:


Bramlette, M. N. & Sullivan, F. R. (1961). Coccolithophorids and related nannoplankton of the Early Tertiary in California. Micropaleontology. 7(2): 129-188. gs


Zygodiscus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 10-12-2023

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

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