Distinguishing features:
Parent taxon (Braarudosphaerales): Nannoliths formed of multiple layers of thin elements, arranged with rotational symmetry, and showing tangential c-axis orientations.
This taxon: 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.
Daughter taxa (time control age-window is: 0-800Ma) | Granddaughter taxa | ||||
Eprolithus Moderately tall, circular to stellate, multiradiate nannoliths with 5-9 petaloid wall-cycle elements surrounding a wide central area spanned by a median diaphragm. Typically H-shaped in side view. | Eprolithus rarus Eprolithus moratus Eprolithus octopetalus Eprolithus floralis Eprolithus apertior Eprolithus antiquus Eprolithus sp. | ||||
Radiolithus Near circular to stellate eprolithids with relatively narrow wall formed from 9-16 brick-like, wall-cycle elements surrounding a wide central area spanned by an amedian diaphragm. The wall is usually lower than those seen in Eprolithus. | Radiolithus laingii Radiolithus hollandicus Radiolithus orbiculatus Radiolithus planus Radiolithus undosus Radiolithus sp. | ||||
Farhania Eprolithid with narrow wall (formed from 16-24 small, brick-like elements) surrounding a wide central area spanned by an amedian diaphragm. | |||||
Lithastrinus Eprolithids with two cycles of five to seven ray-like, curved, wall-cycle elements surrounding a narrow median diaphragm. | Lithastrinus quadricuspis Lithastrinus pentabrachius Lithastrinus grillii Lithastrinus septenarius Lithastrinus sp. | ||||
Uniplanarius Stellate (triradiate or tetraradiate) nannoliths with three or four ray-like elements; there may be a small central diaphragm. | Uniplanarius clarkei Uniplanarius gothicus Uniplanarius sissinghii Uniplanarius trifidus Uniplanarius sp. | ||||
Quadrum 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. | Quadrum gartneri Quadrum svabenickae Quadrum bengalensis Quadrum intermedium Quadrum eptabrachium Quadrum octobrachium Quadrum eneabrachium Quadrum giganteum Quadrum sp. | ||||
Micula Typically cubiform nannoliths usually formed from two superimposed and complexly-intergrown cycles of four pyramidal/blocky elements each | Micula staurophora Micula adumbrata Micula concava Micula cubiformis Micula swastica Micula murus Micula prinsii Micula clypeata Micula praemurus Micula premolisilvae Micula sp. | ||||
Palaeomicula Nannolith formed of four blocks, nannolith shape is approx square with diagonal sutures, elements show tangential crystallographic orientations |
Taxonomy:
For practical purposes including them here is useful since it groups together all the Mesozoic nanoliths with tangential c-axes.
Farinacci & Howe catalog pages: Polycyclolithaceae *
Distinguishing features:
Parent taxon (Braarudosphaerales): Nannoliths formed of multiple layers of thin elements, arranged with rotational symmetry, and showing tangential c-axis orientations.
This taxon: 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.
Morphology:
: nannolith-radiate, |
Lith size: 0->0µm; |
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 Kimmeridgian Stage (149.24-154.78Ma, base in Kimmeridgian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Bown, P. R. & Cooper, M. K. E. (1998). Jurassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 34-85. gs O Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 132-199. gs O Forchheimer, S. (1972). Scanning electron microscope studies of Cretaceous coccoliths from the Köpingsberg Borehole No. 1, SE Sweden. Sveriges Geologiska Undersökning, Series C. #668, 65: 1-141. gs O Perch-Nielsen, K. (1985). Mesozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge (1): 329-426. gs Varol, O. (1992). Taxonomic revision of the Polycyclolithaceae and its contribution to Cretaceous biostratigraphy. Newsletters on Stratigraphy. 27(93-127): -. gsReferences:
Polycyclolithaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 12-11-2024
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10927 Go to Archive.is to create a permanent copy of this page - citation notes |
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