Nannotax3 - ntax_cenozoic - flat-topped


Classification: ntax_cenozoic -> Holococcoliths -> flat-topped
Sister taxa: tubeless, convex, bridged, flat-topped, septate, open-tube, fossil holococcoliths, U. extant holococcolith

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Calyptrosphaera -flat
Monomorphic - cavate
Coccoliths with broad rim and recessed distal cover without boss
C. cialdii
C. dentata

Helicosphaera HOL
Monomorphic; liths solid - formed of layers of crystallites in rhomboid array
Coccolith distal surface with central boss and varying number of depressions.
H. HOL catilliferus type
H. HOL confusus type
H. HOL ponticuliferus type
H. pavimentum HOL

Dimorphic - liths cavate
BCs flat topped with large openings in tube and variable openings in distal surface; tiered wall fabric; low transverse ridge.
CFCs helladoliths - ridge of BCs is extended into prominent leaf, no openings in tube.
P. isselii
P. magnaghii
S. aurisinae HOL
S. gaarderae HOL
P. sp.

S. mediterranea HOL type
Dimorphic - usually cavate
BCs with flat distal cover with or without openings; central boss
CFCs; with irregular bridge or distal cover arched upwards
C. multipora
S. histrica HOL
S. mediterranea HOL gracillima type
S. mediterranea HOL hellenica type
S. mediterranea HOL marisrubri type
S. mediterranea HOL wettsteinii type

Dimorphic; liths semi-solid - formed of concentric rings of crystallites.
BCs flat topped with node or ridge on distal surface, rather than a true bridge.
CFCs similar with transverse bridge or leaf.
S. bannockii HOL
Z. amoena
Z. marsilii
Z. sp.


Citation: Holococcoliths with flat cover over the tube - informal grouping proposed by Young et al., 2003
Rank: informal group of genera

Distinguishing features:
Parent taxon (Holococcoliths): Haploid life-cycle stages, with liths formed of numerous rhombohedral microcrystals
This taxon: Holococcoliths with tube, covered distally by a flat cover

Farinacci & Howe catalog pages: flat-topped [no catalog entry yet]



Search data:
MetricsLith size: 1.6->3.3µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): Extant. Data source: Total of range of species in this database
First occurrence (base): at base of Gelasian Stage (0% up, 2.6Ma, in Piacenzian stage). Data source: Total of range of species in this database

Plot of occurrence data:


Young, J. R., Geisen, M., Cros, L., Kleijne, A., Probert, I. & Ostergaard, J. B. (2003). A guide to extant coccolithophore taxonomy. Journal of Nannoplankton Research, Special Issue. 1: 1-132. gs V O


flat-topped compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 7-7-2022

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

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