Distinguishing features:
Parent taxon (ntax_mesozoic): Mesozoic nannofossils - Cenozoic and extant taxa are in a separate module
This taxon: 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. | Amphizygus Archaeozygodiscus Gorkaea Placozygus Reinhardtites Tranolithus Zeugrhabdotus Chiastozygus Staurolithites Diadorhombus Rhabdophidites Ahmuellerella Bukrylithus Diloma Heteromarginatus Misceomarginatus Monomarginatus Vacherauvillius Braloweria Clepsilithus Crepidolithus Loxolithus Neocrepidolithus Tubirhabdus Chiastozygaceae - unidentified | ||||
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:
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 *
Distinguishing features:
Parent taxon (ntax_mesozoic): Mesozoic nannofossils - Cenozoic and extant taxa are in a separate module
This taxon: Murolith coccoliths with an upper/outer cycle of clockwise-imbricate V-units and a lower/inner cycle of R-units.
Search data:
: murolith, |
Lith size: 0->0µm; |
Geological Range:
Last occurrence (top): at top of NP9 zone (100% up, 55.9Ma, in Ypresian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NT2b subzone (194.83-218.41Ma, base in Norian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
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 O Young, J. R. & Bown, P. R. (1997). Proposals for a revised classification system for calcareous nannoplankton. Journal of Nannoplankton Research. 19(1): 15-47. gs References:
Eiffellithales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 7-11-2024
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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