Nannotax3 - ntax_mesozoic - Chiastozygus

Chiastozygus


Classification: ntax_mesozoic -> Eiffellithales -> Chiastozygaceae -> Chiastozygus
Sister taxa: Amphizygus, Archaeozygodiscus, Gorkaea, Placozygus, Reinhardtites, Tranolithus, Zeugrhabdotus ⟩⟨ Chiastozygus ⟩⟨ Staurolithites, Diadorhombus, Rhabdophidites ⟩⟨ Ahmuellerella, Bukrylithus, Diloma, Heteromarginatus, Misceomarginatus, Monomarginatus, Vacherauvillius ⟩⟨ Braloweria, Clepsilithus, Crepidolithus, Loxolithus, Neocrepidolithus, Tubirhabdus, C. - unidentified

Distinguishing features:
Parent taxon (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.
This taxon: Murolith (loxolith) coccoliths with relatively narrow rim and wide central area spanned by diagonal bars. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic.


Daughter taxa (time control age-window is: 0-800Ma)
unicyclic species
Chiastozygus amphipons
Rim dark, unicyclic; Cross bright, simple
Chiastozygus bifarius
Rim dark unicyclic; Cross complex with distinct median extinction line in XPL.
Chiastozygus litterarius
Rim broad unicyclic or diffusely bicyclic; Cross weakly birefringent
Chiastozygus platyrhethus
Rim dark unicyclic, narrow; Cross bright with a distinct median extinction line in XPL; Central area wide
Chiastozygus spissus
Rim dark with median extinction line; Cross with median extinction line, almost fills central opening
bicyclic species
Chiastozygus antiquus
Rim bicyclic with bright inner cycle and strongly curved isogyres; Cross simple
Chiastozygus garrisonii
Rim narrow, bicyclic; Cross thin, bright; Openings large
Chiastozygus stylesii
Rim bicyclic, bright inner cycle broader; Cross wide, bright and simple; Elongate shape
Chiastozygus trabalis
Rim bicyclic, inner margin denticulate; cross complex, vaulted (centre of cross is above the rim)
less widely used species
Chiastozygus propagulis
Cross H-shaped
Chiastozygus quadriperforatus
Cross defines two small and two large openings
Chiastozygus synquadriperforatus
Cross asymmetric one bar longer than the other,
Chiastozygus tenuis

Chiastozygus sp.
Specimens not identified to species level - AND SPECIES OF UNCERTAIN VALUE

Taxonomy:

Citation: Chiastozygus Gartner, 1968
Rank: Genus
Type species: Zygodiscus amphipons Bramlette and Martini, 1964 designated by Gartner, 1968.

Farinacci & Howe catalog pages: Chiastozygus *

Distinguishing features:
Parent taxon (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.
This taxon: Murolith (loxolith) coccoliths with relatively narrow rim and wide central area spanned by diagonal bars. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic.

Search data:
TagsLITHS: murolith, elliptical, CA: ca_disjunct, process, diagonal cross, CROSS-POLARS: rim-bicyclic, rim-unicyclic, V-prominent, R-prominent,
MetricsLith size: 5->10µm;
Data source notes: size range of included species
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 Maastrichtian Stage (100% up, 66Ma, in Danian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Berriasian Stage (0% up, 145Ma, in Berriasian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Early Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gs

Bramlette, M. N. & Martini, E. (1964). The great change in calcareous nannoplankton fossils between the Maestrichtian and Danian. Micropaleontology. 10(2): 291-322. gs

Gartner, S. (1968). Coccoliths and related calcareous nannofossils from Upper Cretaceous deposits of Texas and Arkansas. University of Kansas Paleontological Contributions, Articles. 48 (Protista 1): 1-56. gs V O


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Chiastozygus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 28-11-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10246 Go to Archive.is to create a permanent copy of this page - citation notes



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