Distinguishing features: Tiered placoliths with 3-5 closely-appressed shields.
Daughter taxa (time control age-window is: 0-800Ma)![]() | Granddaughter taxa | ||||
![]() | Arkhangelskiellaceae Arkhangelskielids with shields predominantly formed of R-units, thus bright in cross-polarised light; V-units often form dark outer rim. | ||||
![]() | ![]() | Kamptneriaceae Arkhangelskielids with shields predominantly formed of V-units, thus dark in cross-polarised light; R-units form bright band at core of shield. |
Taxonomy:
Farinacci & Howe catalog pages: Arkhangelskiales
Distinguishing features: Tiered placoliths with 3-5 closely-appressed shields.
Morphology: 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.
Tags | LITHS: placolith, |
Metrics | Lith size: 0->0µm; |
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): at base of Valanginian Stage (0% up, 139.4Ma, in Valanginian stage). Data source: Total of range of species in this database
Plot of occurrence data:
Bown, P. R. & Young, J. R. (1997). Mesozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 21-36. gs V O Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Early Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gsReferences:
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Arkhangelskiales compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 23-4-2021
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