|Daughter taxa: (blue => in age window 0-800Ma)||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.
Distinguishing features: 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.
|Metrics||Lith size: 4->13.5µm;|
Last occurrence (top): in upper part of Ypresian Stage (67% up, 50.5Ma, in Ypresian stage). Data source: Total of range of species in this database
First occurrence (base): near base of Tithonian Stage (8% up, 151.5Ma, in Tithonian stage). Data source: Total of range of species in this database
Plot of occurrence data:
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