Nannotax3 - ntax_cenozoic - Chiastozygaceae Nannotax3 - ntax_cenozoic - Chiastozygaceae

Chiastozygaceae


Classification: ntax_cenozoic -> Mesozoic Survivors -> Chiastozygaceae
Sister taxa: Biscutaceae, Chiastozygaceae, Watznaueriaceae

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Jakubowskia
Elliptical murolith with narrow rim and wide vacant central area.
Jakubowskia leoniae
Jakubowskia sp.

Neocrepidolithus
Murolith (loxolith) coccoliths with broad, high rim and narrow or closed central-area, which may be spanned by bars.
Neocrepidolithus cohenii
Neocrepidolithus cruciatus
Neocrepidolithus dirimosus
Neocrepidolithus fossus
Neocrepidolithus grandiculus
Neocrepidolithus neocrassus
Neocrepidolithus sp.

Staurolithites
Murolith (loxolith) coccoliths with relatively narrow rim and wide central area spanned by axial cross bars. The cross is usually spine bearing. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic.
Staurolithites primaevus
Staurolithites sp.

Zeugrhabdotus
Murolith (loxolith) coccoliths with central area spanned by variably constructed transverse bar. The bar is usually spine bearing. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic. Delicate lateral bars may also be present but are generally only seen in exceptional preservation.
Zeugrhabdotus recens
Zeugrhabdotus sigmoides
Zeugrhabdotus sp.

Taxonomy:

Citation: Chiastozygaceae Rood et al., 1973
taxonomic rank: Family

Distinguishing features:
Parent taxon (Mesozoic Survivors): Mesozoic taxa which occur in low abundances in the early Palaeogene.
This taxon: Loxolith coccoliths with variably-developed proximal/inner-cycles and a central-area spanned by axial, non-axial or diagonal crossbars or a single transverse bar. LM image includes both unicyclic and bicyclic types. Outer rim clockwise-imbricate.

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


Morphology:

Chiastozygaceae throughout the Mesozoic and in the survivor species show clockwise imbrication of the  outer rim. In contrast the Zygodiscales are an exclusively Cenozoic group, they show  show anti-clockwise imbrication - and also typically have finer elements. So, although both groups form murolith coccoliths, they are morphologically distinct and may be unrealted. 

Search data:
Lith size: 4->13.5µm;
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 NP12 zone (100% up, 50.5Ma, in Ypresian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NJ17a subzone (146.27-148.67Ma, base in Tithonian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:

References:

Rood, A. P., Hay, W. W. & Barnard, T. (1973). Electron microscope studies of Lower and Middle Jurassic coccoliths. Eclogae Geologicae Helvetiae. 66: 365-382. gs O


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Chiastozygaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-4-2024

Taxon Search:
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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=280 Go to Archive.is to create a permanent copy of this page - citation notes
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