Nannotax3 - ntax_cenozoic - Discoasterales Nannotax3 - ntax_cenozoic - Discoasterales

Discoasterales


Classification: ntax_cenozoic -> Discoasterales
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
Discoasteraceae
Discoidal discoasteralids formed of one, non-birefringent in plan view, cycle.
Discoaster
Catinaster
Candeodiscoaster

Fasciculithaceae
Conical or cylindrical discoasteralids consisting of 10-30 wedge-shaped, radially-arranged elements, in one to three superposed cycles.
Diantholitha
Fasciculithus
Gomphiolithus
Lithoptychius
Tectulithus

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

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

Taxonomy:

Citation: Discoasterales Hay, 1977
taxonomic rank: Order
Taxonomic 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.

Distinguishing features:
Parent taxon (ntax_cenozoic): Extant coccolithophores and Cenozoic calcareous nannofossils - Mesozoic nannofossils are in a separate module
This taxon: Radially symmetrical nannoliths formed from one to several separate cycles of elements that radiate from a common centre or axis.

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


Morphology:

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.


Phylogenetic relations

The earliest members of the Discoasterales appear in the Palaeocene and they show more similarities to heterococcoliths -see e.g. Aubry et al. 2011. They also share with radial symmetry and precise control of calcite crystallographic orientation and complex sculpting of individual calcite crystal units. They apparently lack however growth from a proto-coccolith ring and so presence of alternating V- and R-units. Phylogenetically it seems reasonable to infer that they evolved from heterococcoliths by modification of the biomineralisation process.

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): at top of NN18 zone (100% up, 1.9Ma, in Gelasian stage). 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:

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(1): 11-38. gs O

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

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 225-265. gs


nannotaxlogo400px

Discoasterales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-4-2024

Taxon Search:
Advanced Search

Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=517 Go to Archive.is to create a permanent copy of this page - citation notes
nannotaxlogo400px

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


Add Comment

* Required information
Captcha Image
Powered by Commentics

Comments

No comments yet. Be the first!