Distinguishing features:
Parent taxon (Polycyclolithaceae): Nannoliths composed of two superposed wall cycles and a central-area which may be closed, open and vacant, or spanned by a diaphragm-like structure. Elements have tangential c-axis orientation.
This taxon: Stellate to cubiform nannoliths with walls formed from two cycles of 4-9 elements and no central opening or diaphragm. When cubiform, the elements are joined along sutures that go out to the mid-point of the 'cube' edges.
Daughter taxa (time control age-window is: 0-800Ma)![]() | |||||
Q. gartneri and variants | |||||
Quadrum gartneri Cubiform Quadrum with four wall-cycle elements. | |||||
![]() | ![]() | ![]() | ![]() | Quadrum svabenickae Like Q. gartneri but with a central depression and elements that appear to be thickened at the edges. | |
![]() | Quadrum bengalensis Quadrum with one cycle larger than the other. | ||||
species with >4 elements | |||||
![]() | Quadrum intermedium Stellate to cubiform Quadrum with four large wall-cycle elements alternating with one to three smaller wall-cycle elements. | ||||
Quadrum eptabrachium Quadrum with 7 elements per cycle | |||||
Quadrum octobrachium Quadrum with 8 elements per cycle | |||||
Quadrum eneabrachium Quadrum with 9 elements per cycle | |||||
![]() | Quadrum giganteum Large (>10µ) Quadrum with 9 elements per cycle | ||||
Quadrum sp. Specimens not identified to species level |
Taxonomy:
Farinacci & Howe catalog pages: Quadrum + *
Distinguishing features:
Parent taxon (Polycyclolithaceae): Nannoliths composed of two superposed wall cycles and a central-area which may be closed, open and vacant, or spanned by a diaphragm-like structure. Elements have tangential c-axis orientation.
This taxon: Stellate to cubiform nannoliths with walls formed from two cycles of 4-9 elements and no central opening or diaphragm. When cubiform, the elements are joined along sutures that go out to the mid-point of the 'cube' edges.
Morphology:
Size:
Tags | LITHS: nannolith-radiate, quadrate, star-shaped, CA: closed, CROSS-POLARS: T-prominent, |
Metrics | Lith size: 3->14µm; 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 range of species in this database
First occurrence (base): in lower part of Albian Stage (22% up, 110.2Ma, in Albian stage). Data source: Total of range 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 Manivit, H., Perch-Nielsen, K., Prins, B. & Verbeek, J. W. (1977). Mid Cretaceous calcareous nannofossil biostratigraphy. Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen. B80(3): 169-181. gsReferences:
![]() |
Quadrum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-5-2022
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10966 Go to Archive.is to create a permanent copy of this page - citation notes |
Comments
(0)