Discoasterales


Ancestry: Coccolithophores -> Discoasterales
Sister taxa: Isochrysidales, Coccolithales, Zygodiscales, Syracosphaerales, Coccolith families inc sed, Holococcoliths, Discoasterales, Nannolith families inc sed, Mesozoic Survivors, hidden,

Short diagnosis: Radially symmetrical nannoliths formed from one to several separate cycles of elements that radiate from a common centre or axis.


Daughter taxa (blue => in age window 0-300Ma) Granddaughter taxa
Discoidal discoasteralids formed of one, non-birefringent in plan view, cycle.

Conical or cylindrical discoasteralids consisting of 10-30 wedge-shaped, radially-arranged elements, in one to three superposed cycles.

Discoidal discoasteralids with several distinct cycles including at least one that is birefringent.

Conical discoasteralids with a concave base, consisting of a mass of elements radiating from a common origin.

Taxonomy:

Citation: Discoasterales Hay, 1977
Rank: Order
Notes & discussion: Hay (1977) described the Order Discoasterales as a broad taxonomic group that included most radial and stellate Mesozoic and Cenozoic nannoliths. It is used here as a narrower taxonomic concept that incorporates the type family, the Discoasteraceae, together with the other radially symmetrical Paleogene nannolith groups, the Heliolithaceae, Fasciculithaceae and Sphenolithaceae, which originated within four million years of one another and have common morphological features suggesting phylogenetic affinity (Bown 2010).
The term discoasteralids is used here as a concise term for nannoliths produced by members of the order Discoasterales.

Farinacci & Howe catalog pages:

Short diagnosis: Radially symmetrical nannoliths formed from one to several separate cycles of elements that radiate from a common centre or axis.


Morphology remarks: Includes disc-like (discoasters), stellate (discoasters), cylindrical (fasciculiths, helioliths and sphenoliths) and conical (fasciculiths and sphenoliths) morphologies, but all with rotational symmetry about a single axis. The top and bottom surfaces, relative to the axis of rotation are usually different and one surface is normally concave and is considered proximal. All members show complex crystal units with control of both a-axis and c-axis orientation. The structures are often chiral.

Geological Range:
Last occurrence (top): within Gelasian Stage (1.81-2.59Ma, top in Gelasian stage). Data source: Total of range of species in this database
First occurrence (base): within Danian Stage (61.61-66.04Ma, base in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R., (2010). Calcareous nannofossils from the Paleocene/Eocene Thermal Maximum interval of southern Tanzania (TDP Site 14). Journal of Nannoplankton Research, 31: 11-38.

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

Perch-Nielsen, K., (1985). Cenozoic calcareous nannofossils. In: Bolli, H.M., Saunders, J.B. and Perch-Nielsen, K. (Editors), Plankton Stratigraphy. Cambridge University Press, Cambridge, pp. 427-555.

Young, J.R., (1998). Neogene. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 225-265.


Nannotax3 - Coccolithophores - Discoasterales by: Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 30-3-2017

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