arrayname: original
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 with distal/outer-cycle that shows little or no imbrication and central area spanned by transverse bars; rim exhibits spiral interference pattern.
Daughter taxa (time control age-window is: 0-800Ma)![]() | ||||
![]() | ![]() | Placozygus banneri Small Placozygus (holotype 4.4 µm) with crossbar dark in xpl and almost filling the central area | ||
![]() | Placozygus fibuliformis Like P. spiralis but bar fills less of central area and formed of multiple elements | |||
![]() | Placozygus spiralis | |||
![]() | Placozygus sp. Specimens not identified to species level |
Taxonomy:
Farinacci & Howe catalog pages: Placozygus *
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 with distal/outer-cycle that shows little or no imbrication and central area spanned by transverse bars; rim exhibits spiral interference pattern.
Search data:
LITHS: murolith, elliptical, CA: bar, process, ca_disjunct, CROSS-POLARS: R-prominent, V-prominent, rim-bicyclic, |
Lith size: 3.5->8µm; Data source notes: size range of included species |
Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Danian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within UC9b subzone (89.49-89.95Ma, base in Turonian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 132-199. gs O Hoffmann, N. (1970a). Placozygus n. gen. (Coccolithineen) aus der Oberkreide des nordlichen Mitteleuropas. Geologie, Berlin. 19: 1004-1009. gsReferences:
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Placozygus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 23-3-2025
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10908 Go to Archive.is to create a permanent copy of this page - citation notes |
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