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 butwith a central depression and elements that appear to be thickened at the edges.
Quadrum sp. Specimens not identified to species level
Taxonomy:
Citation: Quadrum Prins & Perch-Nielsen in Manivit et al., 1977Rank: GenusType species: Quadrum gartneri Prins & Perch-Nielsen in Manivit et al., 1977Taxonomic discussion: The Quadrum species with more than 4 elements are very similar to the species of Lithastrinus with the same number of elements and have similar ranges so the distinction between them may be artificial.
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.
Lith size: 3->14µm; Data source notes: size range of included species
The morphological data given here can be used on the advanced search page. See also these notes
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:
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
Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 132-199. gsO
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. gs
Quadrum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-5-2022
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