Nannotax3 - ntax_mesozoic - Polycyclolithaceae

Polycyclolithaceae


Classification: ntax_mesozoic -> Braarudosphaerales -> Polycyclolithaceae
Sister taxa: Braarudosphaeraceae, Transitional genera, Nannoconaceae ⟩⟨ Polycyclolithaceae, Other nannoliths with tangential c-axes

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.
E. rarus
E. moratus
E. octopetalus
E. floralis
E. apertior
E. antiquus
E. 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.
R. laingii
R. hollandicus
R. orbiculatus
R. planus
R. undosus
R. sp.

Farhania
Eprolithid with narrow wall (formed from 16-24 small, brick-like elements) surrounding a wide central area spanned by an amedian diaphragm.
F. varolii
F. sp.

Lithastrinus
Eprolithids with two cycles of five to seven ray-like, curved, wall-cycle elements surrounding a narrow median diaphragm.
L. quadricuspis
L. pentabrachius
L. grillii
L. septenarius
L. sp.

Uniplanarius
Stellate (triradiate or tetraradiate) nannoliths with three or four ray-like elements; there may be a small central diaphragm.
U. clarkei
U. gothicus
U. sissinghii
U. trifidus
U. 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.
Q. gartneri
Q. svabenickae
Q. bengalensis
Q. intermedium
Q. eptabrachium
Q. octobrachium
Q. eneabrachium
Q. giganteum
Q. sp.

Micula
Typically cubiform nannoliths usually formed from two superimposed and complexly-intergrown cycles of four pyramidal/blocky elements each

Palaeomicula
Nannolith formed of four blocks, nannolith shape is approx square with diagonal sutures, elements show tangential crystallographic orientations
P. jacovidesii
P. maltica
P. quadrisphena

Taxonomy:

Citation: Polycyclolithaceae Forchheimer, 1972 emend Varol, 1992
Rank: Family

Taxonomic discussion:
The Polycyclolithiaceae are tentatively included here in the Braarudospharales (sensu Lees & Bown 2016) since they also have tangential c-axes, and simple rotational symmetry, and the earliest form (e.g. Eprolithus apertior) show simlar cyclindrical shapes to nannoconids. [my interpretation - JRY 2019]
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 [no catalog entry yet]

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: This family has previously been used for a wide variety of nannoliths with circular to stellate, multiradiate morphologies (e.g. Perch-Nielsen, 1985). Varol (1992) redefined the family to include only those forms which appear to represent a phylogenetic grouping, and this is followed below. Those forms which do not fall into this category are placed in the nannoliths incertae sedis.

Search data:
TagsLITHS: nannolith-radiate,
MetricsLith size: 0->0µm;
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): at base of Kimmeridgian Stage (0% up, 157.3Ma, in Oxfordian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

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

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

Perch-Nielsen, K. (1985b). Mesozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 329-426. gs

Varol, O. (1992b). Taxonomic revision of the Polycyclolithaceae and its contribution to Cretaceous biostratigraphy. Newsletters on Stratigraphy. 27(93-127): -. gs


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Polycyclolithaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 18-10-2021

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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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