Nannotax3 - ntax_main - Holococcoliths

Citation: Holococcoliths of Young et al. 2003

Taxonomic rank: informal group of families

Taxonomic discussion:

It used to be conventional to place all holococcoliths in the Famly Calyptrosphaeraceae, however this is manifestly artificial, since it is now known that holococcoliths are formed during the haploid life-cycle stage of species belonging to numerous different families. Moreover, the type species of the Family Calyptrosphaeraceae, Calyptrosphaera oblonga, is now known to be a life-cycle phase of Syracosphaera pulchra, hence the name Calyptrosphaeraceae is a junior synonym of Syracosphaeraceae.
It is still convenient to group the holococcoliths together for identification purposes, but giving this artificial grouping a formal taxonomic name (e.g. Calyptrosphaeraceae, Zygosphaerales, Zygrhablithales) is no longer defensible.
Similarly the generic classification is increasingly anachronistic as more life-cycle combinations are discovered. We do still use traditional names but the groupings used here are larely based on coccolithi shape, since this is the easiest criterion for organising taxa and since there appears to be little correlation between any aspects of holococcolithophorid morphology and phylogeny.

Distinguishing features:
Parent taxon (ntax_main):
This taxon: Haploid life-cycle stages, with liths formed of numerous rhombohedral microcrystals

Holococcoliths are formed of numerous, minute (ca 0.1 µm) rhombohedral calcite crystallites (Young & Henriksen 2003). They are produced during the haploid phase of the life-cycle of a wide range of coccolithophores that bear heterococcoliths in their diploid life-cycle phase.

Intracellular calcification
Holococcolith formation has long been suggested to occur outside the cell (e.g Rowson et al. 1986). However Langer et al. (2021) illustrated intracellular holococcolith formation in Coccolithus and this was confirmed by work of Ben Joseph et al. (2023) and by Meyer & Taylor (2025). Notably Meyer & Taylor (2025) showed well-formed holococcoliths inside C. leptoporus haploid cells.

Although diverse holococcolith assemblages have been described from Cretaceous and Palaeogene assemblages, they are virtually absent from Neogene nannofloras. This is rather surprising, given that modern nannofloras include >60 holococcolithophores (see, e.g., Kleijne, 1991; Jordan & Kleijne, 1994; Young et al. 2003), but most species produce very small holococcoliths (often <2µm) with low preservation potential.

References:

Ben-Joseph, O., et al. (2023). Crystallization of coccolith calcite at different life-cycle phases exhibits distinct degrees of cellular confinement. Small Structures. 4: 1-9. gs

Boudreaux, J. E. & Hay, W. W. (1969). Calcareous nannoplankton and biostratigraphy of the late Pliocene-Pleistocene-Recent sediments in the Submarex cores. Revista Española de Micropaleontología. 1(3): 249-292. gs O

Hay, W. W. (1977). Calcareous nannofossils. In, Ramsay, A. T. S. (ed.) Oceanic Micropalaentology. Academic Press, London (2): 1055-1200. gs

Hay, W. W., Mohler, H. P., Roth, P. H., Schmidt, R. R. & Boudreaux, J. E. (1967). Calcareous nannoplankton zonation of the Cenozoic of the Gulf Coast and Caribbean-Antillean area, and transoceanic correlation. Transactions of the Gulf-Coast Association of Geological Societies. 17: 428-480. gs O

Jordan, R. W. & Kleijne, A. (1994). A classification system for living coccolithophores. In, Winter, A. & Siesser, W. G. (eds) Coccolithophores. Cambridge University Press, Cambridge 83-105. gs

Kleijne, A. (1991). Holococcolithophorids from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean. Marine Micropaleontology. 17: 1-76. gs

Langer, G., et al. (2021). Role of silicon in the development of complex crystal shapes in coccolithophores. New Phytologist. New Phytologist. 1-13. gs

Meyer, E. M. & Taylor, A. R. (2025). A comparison of calcification mechanisms in haploid and diploid cells of the coccolithophore Calcidiscus leptoporus (Murray & Blackman 1898). Journal of Phycology. 1-19. gs

Rowson, J. D., Leadbeater, B. S. C. & Green, J. C. (1986). Calcium carbonate deposition in the motile (Crystallolithus) phase of Coccolithus pelagicus (Prymnesiophyceae). British Phycological Journal. 21: 359-370. gs

Varol, O. (2025). A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222. gs

Young, J. R. & Henriksen, K. (2003). Biomineralization within vesicles: the calcite of coccoliths. Reviews in Mineralogy and Geochemistry. 54(1): 189-215. gs

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. S1: 1-132. gs

Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	tubeless Holococcoliths without a tube, flat or cap-shaped	Sphaerocalyptra Syracosphaera HOL (Anthosphaera type) fried egg monomorphic flat dimorphic flat (coccolithaceae HOLs) flat trapezoidal tubeless-minute
	convex Holococcoliths with tube, covered distally by a convex cover	Calyptrosphaera sphaeroidea HOL Syracosphaera pulchra HOL oblonga type Syracosphaera pulchra HOL pirus type Syracosphaera pulchra HOL galea type Calyptrolithina divergens Calyptrosphaera lluisae Calyptrosphaera heimdaliae Flosculosphaera Gliscolithus Calyptrosphaera radiata Calyptrosphaera sp. strain RCC1181
	bridged Holococcoliths with tube, spanned distally by a bridge	Corisphaera Helladosphaera Homozygosphaera Poritectolithus Syracosphaera anthos HOL
	flat-topped Holococcoliths with tube, covered distally by a flat cover	Helicosphaera HOL Holococcolithophora -flat S. aurisinae HOL type S. mediterranea HOL type Zygosphaera
	septate Holococcoliths with tube, open distally and subdivided internally by vertical septae	Calcidiscus leptoporus subsp. quadriperforatus HOL Scyphosphaera apsteinii HOL Pontosphaera japonica HOL Syracolithus sp. type A Syracolithus sp. type B Syracolithus bicorium
	open-tube Holococcoliths with tube, open distally (or cover recessed)	Calicasphaera Papposphaera HOL Trigonaspis
	fossil holococcoliths Holococcolith genera only known from the fossil record	Daktylethra Holodiscolithus Lanternithus Multipartis Octolithus Quadrilateris Semihololithus Varolia Youngilithus Zygrhablithus Aubrysphaera Corannulus Orthozygus Peritrachelina Unidentified fossil holococcoliths
	Unidentified extant holococcolith

Holococcoliths

References:

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