Nannotax3 - ntax_cenozoic - Zygodiscales Nannotax3 - ntax_cenozoic - Zygodiscales


Classification: ntax_cenozoic -> Zygodiscales
Sister taxa: Isochrysidales, Coccolithales, Zygodiscales, Syracosphaerales, Coccolith families inc sed, Mesozoic Survivors ⟩⟨ Holococcoliths, Braarudosphaerales, Discoasterales, Nannolith families inc sed, hidden

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Varimorphic; liths placolith-like but with helical shield structure; arranged in spiral on coccosphere

Monomorphic or dimorphic; liths muroliths with perforate central area

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).


Citation: Zygodiscales Young & Bown, 1997
taxonomic rank: Order
Taxonomic discussion: Taxa included: The extant families Helicosphaeraceae and Pontosphaeraceae and extinct Family Zygodiscaceae. These show highly variable shape, but similar structure, and there is strong palaeontological evidence for their evolutionary connections (Romein 1979; Aubry 1989).

Distinguishing features:
Parent taxon (ntax_cenozoic): Extant coccolithophores and Cenozoic calcareous nannofossils - Mesozoic nannofossils are in a separate module
This taxon: 2N: Heterococcoliths with V-units forming upper/outer cycle of imbricated elements and R-units forming basal plate and central mass of irregular elements. Usually motile
N: Form holococcoliths formed of single block

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


Coccolith structure: V-units form outer rim; in Pontosphaeraceae and Zygodiscaceae, this is a narrow cycle of anticlockwise-imbricating elements, in the Helicosphaeraceae, a helical flange. The R-units form a proximal plate of rather regular, inward-growing elements and a distal blanket, which typically appears as a mass of minute, tangentially-elongated crystallites. Growth does not occur downwards from the proto-coccolith ring and so the alternating belt of V-R nuclei remains clearly visible on the proximal surface.

Biology & life-cycles

Helicosphaera carteri has been cultured repeatedly (Inouye pers. comm., Probert unpubl. data) and Scyphosphaera apsteinii once (Probert unpubl. data). Life-cycle transitions have been observed in Helicosphaera cultures, and combination coccospheres have been observed for Helicosphaera (Cros et al. 2000, Geisen et al. 2002), Pontosphaera and Scyphosphaera (Frada et al. 2009). These indicate that the haploid phase forms holococcoliths with distinctive rhomboid-array ultrastructure - these were previously placed in the genus Syracolithus.

Search data:
Lith size: 0->0µm;
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 NP1 zone (65.47-66.04Ma, base in Danian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:


Aubry, M. -P. (1989a). Handbook of Cenozoic calcareous nannoplankton. Book 3: Ortholithae (Pentaliths, and others), Heliotithae (Fasciculiths, Sphenoliths and others). Micropaleontology Press, American Museum of Natural History, New York. 1-279. gs

Cros, L., Kleijne, A., Zeltner, A., Billard, C. & Young, J. R. (2000b). New examples of holococcolith-heterococcolith combination coccospheres and their implications for coccolithophorid biology. In, Young, J. R., Thierstein, H. R. & Winter, A. (eds) Nannoplankton ecology and palaeocology, Proceedings of the INA7 conference, Puerto Rico, February 1998. Marine Micropaleontology . 39(1-4): 1-34. gs

Frada, M., Percopo, I., Young, J. R., Zingone, A., de Vargas, C. & Probert, I. (2009). First observations of heterococcolithophore-holococcolithophore life cycle combinations in the family Pontosphaeraceae (Calcihaptophycideae, Haptophyta). Marine Micropaleontology. 71(1): 20-27. gs

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

Perch-Nielsen, K. (1985). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 427-555. gs

Romein, A. J. T. (1979). Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletin. 22: 1-231. gs O

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


Zygodiscales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 24-5-2024

Taxon Search:
Advanced Search

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

Nannotax is being sponsored through 2024 by Woodside Energy and Shell USA

Add Comment

* Required information
Captcha Image
Powered by Commentics


No comments yet. Be the first!