Classification: ntax_cenozoic -> Coccolithales -> Coccolithaceae -> Hughesius
Sister taxa: Coccolithus, Bramletteius, Campylosphaera, Chiasmolithus, Coronocyclus, Cruciplacolithus, Ericsonia, Solidopons ⟩⟨ Birkelundia, Clausicoccus, Craticullithus, Hughesius, Kilwalithus

Daughter taxa (time control age-window is: 0-800Ma)
Hughesius gizoensis
Very small species of Hughesius (<4µm), with 2 rounded plates in central-area, separated by transverse suture.
Hughesius tasmaniae
Small-sized species of Hughesius (3-5µm long), with 4 plates in central-area.
Hughesius youngii
Very small species of Hughesius (<4µm), with 2 elongate plates in central-area, separated by transverse suture.
Hughesius sp.
Specimens which cannot be assigned to established species


Citation: Hughesius Varol, 1989
Rank: Genus
Type species: H. gizoensis Varol 1989
Synonyms: Clausibella Aubry in Aubry & Bord 2009 - name proposed, in effect, for larger members of Hughesius, lacking the distal tube cycl bu with a two layerd proximal shield.
Taxonomic discussion: There appears to be a lineage extending from Clausicoccus fenestratus via H. tasmaniae to H. gizoensis, involving size decrease and reduction of the R-units. H. tasmaniae is very similar to Clausicoccus and essentially is Clausicoccus without prominent birefringent tube, H. gizoensis seems to have a simpler shield structure, possibly as a result of the smaller size.

Distinguishing features: Placolith coccoliths showing low birefringence with central area filled by 2 to 4 plates. Lacks a clearly birefringent distal tube cycle

Farinacci & Howe catalog pages: Hughesius *

Morphology: In Clausicoccus, as in most Coccolithaceae, the distal tube cycle forms a bright ring between the distal shield and the central area. This is absent in Hughesius. 

Search data:
TagsLITHS: placolith, elliptical, CA: closed,
CSPH: equant, monomorphic,
MetricsLith size: 2->5µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): near top of Messinian Stage (86% up, 5.6Ma, in Messinian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Rupelian Stage (0% up, 33.9Ma, in Rupelian stage). Data source: Total of range of species in this database

Plot of occurrence data:


Aubry, M. -P. & Bord, D. (2009). Reshuffling the cards in the photic zone at the Eocene/Oligocene boundary. In, Koeberl, C. & Montanari, A. (eds) The Late Eocene Earth—Hothouse, Icehouse, and Impacts. Geological Society of America, Special Papers. 452: 279-301. gs

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 V O

Varol, O. (1989a). Calcareous nannofossil study of the central and western Solomon Islands. Circum-Pacific Council for Energy and Mineral Resources Earth Sciences. 239-268. gs V O


Hughesius compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 15-5-2021

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