Arkhangelskiales


Classification: Mesozoic -> Arkhangelskiales
Sister taxa: Arkhangelskiales, Eiffellithales, Stephanolithiales, Podorhabdales, Watznaueriales, Syracosphaerales, Heterococcoliths inc sedis, Holococcoliths, Braarudosphaerales, Nannoliths inc sedis, Mesozoic non–coccoliths, hidden,

Short diagnosis: Tiered placoliths with 3-5 closely-appressed shields.


Daughter taxa (blue => in age window 0-300Ma) Granddaughter taxa
Arkhangelskielids with shields predominantly formed of R-units, thus bright in cross-polarised light; V-units often form dark outer rim.

Arkhangelskielids with shields predominantly formed of V-units, thus dark in cross-polarised light; R-units form bright band at core of shield.

Taxonomy:

Citation: Arkhangelskiales Bown & Hampton, 1997 in Bown & Young, 1997
Rank: Order

Farinacci & Howe catalog pages: Arkhangelskiales [no catalog entry yet]

Short diagnosis: Tiered placoliths with 3-5 closely-appressed shields.


Morphology remarks: Central-area structures include transverse bars with proximal net; axial or near axial crosses with proximal net; and perforate plates crossed by axial or near axial sutures. LM images vary significantly, from predominantly dark in the Kamptneriaceae, to predominantly bright in the Arkhangelskiellaceae.
The Kamptneriaceae appears to have originated from loxolith coccoliths, and the tiered placolith rim structure is actually a modified loxolith construction. The earliest representatives of the family are only slightly modified loxolith coccoliths.

Geological Range:
Last occurrence (top): within Maastrichtian Stage (66.04-72.05Ma, top in Maastrichtian stage). Data source: Total of range of species in this database
First occurrence (base): within Valanginian Stage (133.88-139.39Ma, base in Valanginian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R. & Young, J.R., (1997). Mesozoic calcareous nannoplankton classification. Journal of Nannoplankton Research, 19(1): 21-36.

Bown, P.R.; Rutledge, D.C.; Crux, J.A. & Gallagher, L.T., (1998). Early Cretaceous. In: Bown, P.R. (Editor), Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. Chapman & Hall, pp. 86-131.


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Arkhangelskiales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-12-2017

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