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.
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.
Citation: Chiastozygaceae Rood et al., 1973Rank: 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.
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): 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:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: this is a higher taxon page so Neptune data is not plotted. For the customisable plot option go to a genus page Parent: Mesozoic Survivors
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. gsO
Chiastozygaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 8-6-2023
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