Eiffellithales


Classification: ntax_mesozoic -> Eiffellithales
Sister taxa: Arkhangelskiales, Eiffellithales, Stephanolithiales, Podorhabdales, Watznaueriales, Syracosphaerales, Heterococcoliths inc sedis ⟩⟨ Holococcoliths, Braarudosphaerales, Nannoliths inc sedis, Mesozoic non–coccoliths, hidden

Distinguishing features: Murolith coccoliths with an upper/outer cycle of clockwise-imbricate V-units and a lower/inner cycle of R-units. 


Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Chiastozygaceae
Typical Eiffelithales - rim with well outer/upper clockwise-imbricate V-units and lower/inner R-units. Central area open or spanned by disjunct cross or bar supporting a spine.

Eiffellithaceae
Eiffelithales in which V-units form a narrow outer rim; R-units form broad inner rim or plate. Almost all with a disjunct central spine-bearing cross.

Rhagodiscaceae
Eiffelithales with V-units forming most of rim (R-units typically thin plates on proximal surface, so LM images are typically unicyclic. Central-areas typically filled by a plate of granular calcite. The central structure may be spine-bearing, perforate or massive.

Taxonomy:

Citation: Eiffellithales Rood et al., 1971
Rank: Order
Taxonomic discussion: This is a fairly well-characterised group with a common structure of a rim formed of an outer/upper cycle of clockwise imbricate elements. These elements are typically thin and closely spaced and are inclined at about 30-40° from he horizontal. They have sub-vertical c-axes and so show very low birefringence in plan view. On the proximal surface the V-units  are underlain by a cycle of R-units with radial sutures. The r-units also extend up the inside of the rim. This rim type may also be refered to as Eiffelithid or loxolith. 

If the R-units are well-developed then they will be visible in distal view as a separate cycle in SEM imagesand the coccolith will show in cross-polars a birefringent inner cycle. Conversely if they are weakly developed the entire coccolith rim will show low birefringence - these are refered to as respectively bicyclic and unicyclic appearance.

Inside the rim almost all Eiffellithales have additional disjunct structures usually forming a crossbar or central cross, and a spine.  

Most genera are placed in the Chiastozygaceae, with two sub-groups separated out, the Eiffelithaceae and Rhagodiscaceae. In the Eiffellithaceae the V-units form a narrow rim while the R-units extend inward forming a strongly bicyclic rim and often a biefrngent central plate. In the Rhagodiscaceae, by contrast, the R-units are weakly developed, the rim is unicyclic and the central structure is typically granular and shows low birefringence. Distinct crossbar or cross structures are lacking but there is often a, hollow, central spine. Within the Chiastozygaceae most genera include both unicyic and bicyclic forms.

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

Distinguishing features: Murolith coccoliths with an upper/outer cycle of clockwise-imbricate V-units and a lower/inner cycle of R-units. 

Search data:
TagsLITHS: murolith,
MetricsLith 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 base of Ypresian Stage (1% up, 55.9Ma, in Ypresian stage). Data source: Total of range of species in this database
First occurrence (base): in mid part of Norian Stage (50% up, 218.9Ma, in Norian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P. R. (1998b). Triassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 29-33. gs

Rood, A. P., Hay, W. W. & Barnard, T. (1971). Electron Microscope Studies of Oxford Clay Coccoliths. Eclogae Geologicae Helvetiae. 64: 245-272. gs V O


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Eiffellithales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-4-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10405 Go to Archive.is to create a permanent copy of this page - citation notes



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