Nannotax3 - ntax_cenozoic - Calcidiscaceae Nannotax3 - ntax_cenozoic - Calcidiscaceae


Classification: ntax_cenozoic -> Coccolithales -> Calcidiscaceae
Sister taxa: Coccolithaceae, Calcidiscaceae ⟩⟨ Hymenomonadaceae, Pleurochrysidaceae

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Circular or sub-circular; central area closed or with narrow opening
C. leptoporus group
C. pacificanus group
Calcidiscus sp.

Coccoliths polygonal, thin; proximal shield much smaller than distal
Hayaster perplexus
Hayaster cf. perplexus
Hayaster sp.

Coccoliths asymmetric, tube and proximal shield offset from centre of distal shield
Oolithotus antillarum
Oolithotus fragilis
Oolithotus sp.

Central area open

Coccoliths elliptical, grill in central area
Cryptococcolithus mediaperforatus
Cryptococcolithus sp.

Coccoliths cylindrical, with shields separated by an elevated tube
Hayella challengeri
Hayella gauliformis
Hayella simplex
Hayella situliformis
Hayella sp.


Citation: Calcidiscaceae Young & Bown, 1997
taxonomic rank: Family
Taxonomic discussion: Genera included:
NB All these genera were included within the Coccolithaceae in older classifications but were separated by Young & Bown (1987) into the family Calcidscaceae on the grounds of them sharing a simpler coccolith structure than that of the Coccolithaceae. The grouping has been supported by molecular genetic data (Sáez et al., 2003, 2004).

Distinguishing features:
Parent taxon (Coccolithales): 2N: Mostly placolith heterococcoliths with V-unit forming the distal shield; R-unit the proximal shield. Non-motile
N: Form holococcoliths formed of single block, or non-calcifying

This taxon: 2N: cells non-motile, bearing placoliths with R-unit confined to proximal shield, mostly circular.
N: cells motile, holococcolith-bearing

Farinacci & Howe catalog pages: Calcidiscaceae [no catalog entry yet]


Coccoliths are placoliths with rim structure similar to Calcidiscus, i.e. the V-unit forms distal shield and central-area/tube; R-unit forms proximal shield only. As in the Coccolithaceae, growth occurs downward from the proto-coccolith ring which becomes embedded within the structure so that alternating V- and R-units are only visible on specimens where the proximal shield has broken off (Young et al. 2004).
Distal shield sutures usually show laevogyral curvature. The proximal shield is usually formed of a single layer of elements with sub-radial sutures; sometimes a lower layer is developed, with elements showing strong dextral obliquity (in proximal view). The connection between the proximal and distal shields is weak and they frequently separate.

Biology & life-cycles

Dominant phase of life-cycle non-motile with placolith heterococcoliths. Holococcolith bearing motile phase has been documented in the extant species C. leptoporus and C. quadriperforatus (refs. Geisen et al. 2002, Houdan et al. 2004). However, although strains of Umbilicosphaera, and Oolithotus have been successfully cultured for long periods life-cycle transitions have not been obsrved in them (Probert pers. comm.), nor have combination coccospheres been recorded in field samples.

Search data:
Lith size: 2.5->15µm;
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 ranges of the species in this database
First occurrence (base): within NP4 zone (61.51-63.25Ma, base in Danian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:


Geisen, M., Billard, C., Broerse, A. T. C., Cros, L., Probert, I. & Young, J. R. (2002a). Life-cycle associations involving pairs of holococcolithophorid species: intraspecific variation or cryptic speciation? European Journal of Phycology. 37: 531-550. gs

Houdan, A. et al. (2004a). Flow cytometric analysis of relative ploidy levels in holococcolithophore-heterococcolithophore (Haptophyta) life cycles. Systematics and Biodiversity. 1(4): 453-465. gs

Sáez, A. G., Probert, I., Geisen, M., Quinn, P., Young, J. R. & Medlin, L. K. (2003). Pseudo-cryptic speciation in coccolithophores. Proceedings of the National Academy of Sciences, USA. 100(12): 7163-7168. gs

Sáez, A. G., Probert, I., Young, J. R., Edvardsen, B., Wenche, E. & Medlin, L. K. (2004). A review of the phylogeny of the Haptophyta. In, Thierstein, H. R. & Young, J. R. (eds) Coccolithophores - from molecular processes to global impact. Springer, Berlin 251-270. gs

Young, J. R. & Bown, P. R. (1997). Cenozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 36-47. gs

Young, J. R., Henriksen, K. & Probert, I. (2004). Structure and morphogenesis of the coccoliths of the CODENET species. In, Thierstein, H. R. & Young, J. R. (eds) Coccolithophores - From molecular processes to global impact. Springer, Berlin 191-216. gs O


Calcidiscaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-2-2024

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