Quadrum


Classification: Mesozoic -> Braarudosphaerales -> Polycyclolithaceae -> Quadrum
Sister taxa: Eprolithus, Radiolithus, Farhania, Lithastrinus, Uniplanarius, Quadrum, Micula, Palaeomicula,

Distinguishing features: 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: (blue => in age window 0-800Ma)
Q. gartneri and variants
Cubiform Quadrum with four wall-cycle elements.
Like Q. gartneri but with a central depression and elements that appear to be thickened at the edges.
Quadrum with one cycle larger than the other.
species with >4 elements
Stellate to cubiform Quadrum with four large wall-cycle elements alternating with one to three smaller wall-cycle elements.
Quadrum with 7 elements per cycle
Quadrum with 8 elements per cycle
Quadrum with 9 elements per cycle
Large (>11ยต) Quadrum with 9 elements per cycle
Specimens not identified to species level

Taxonomy:

Citation: Quadrum Prins & Perch-Nielsen in Manivit et al., 1977
Rank: Genus
Type species: Quadrum gartneri Prins & Perch-Nielsen in Manivit et al., 1977
Notes & 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.

Farinacci & Howe catalog pages: Quadrum + *

Distinguishing features: 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.

Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Maastrichtian 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:

References:

Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 132-199. gs

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


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Quadrum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 10-12-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10966 Go to Archive.is to create a permanent copy of this page - citation notes



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