Chiastozygaceae


Ancestry: Coccolithophores -> Mesozoic Survivors -> Chiastozygaceae
Sister taxa: Biscutaceae, Chiastozygaceae, Markalius, Watznaueriaceae,

Short diagnosis: 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.


Daughter taxa (blue => in age window 0-300Ma) Granddaughter taxa
Elliptical murolith with narrow rim and wide vacant central area.

Murolith (loxolith) coccoliths with broad, high rim and narrow or closed central-area, which may be spanned by bars.

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.

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.

Taxonomy:

Citation: Chiastozygaceae Rood et al., 1973
Rank: Family

Farinacci & Howe catalog pages:

Short diagnosis: 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.


Morphology remarks: Chiastozygaceae throughout the Mesozoic and in the survivor species show clockwise imbrication of the  outer rim. In contrast the Zygodiscales show anti-clockwise imbrication - and also typically have finer elements.

Geological Range:
Last occurrence (top): within Ypresian Stage (47.84-55.96Ma, top in Ypresian stage). Data source: Total of range of species in this database
First occurrence (base): within Tithonian Stage (145.01-152.06Ma, base in Tithonian stage). Data source: Total of range 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.


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Chiastozygaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-8-2017

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