Distinguishing features: Parent taxon (Arkhangelskiales): Tiered placoliths with 3-5 closely-appressed shields. This taxon: Arkhangelskielids with shields predominantly formed of V-units, thus dark in cross-polarised light; R-units form bright band at core of shield.
Daughter taxa (time control age-window is: 0-800Ma)
Granddaughter taxa
Crucicribrum Tiered coccoliths with perforate central-area plate and axial cross and/or sutures.
Gartnerago Tiered coccoliths with distinctive LM images consisting of a narrow to moderately-broad rim with a narrow, dark outer-cycle; a diagnostic, bright median-cycle; and a dark, inner-cycle. Central-area structures variable but generally dark in LM.
Kamptnerius Tiered placoliths with broad rim that has an asymmetric flange forming a wing and narrow central area spanned by a perforate plate. Typical kamptneriacean LM image with a narrow, dark outer-cycle; a diagnostic, bright median-cycle; a dark, inner-cycle; and a dark central area plate.
Distinguishing features: Parent taxon (Arkhangelskiales): Tiered placoliths with 3-5 closely-appressed shields. This taxon: Arkhangelskielids with shields predominantly formed of V-units, thus dark in cross-polarised light; R-units form bright band at core of shield.
Morphology: Tiered placoliths and modified loxolith coccoliths, with distinctive LM images consisting of a narrow to moderately-broad rim with a narrow, dark outer-cycle; a diagnostic, bright median-cycle; and a dark, inner-cycle. Central-area structures are generally dark in LM, and may be a transverse bar, axial or diagonal cross bars or plate, usually perforate; proximally-situated fine nets may be seen when preservation is good. Rim structure varies from apparently typical loxolith (e.g. Thierstein, 1974: pl.4, figs 1, 9, 12) to placolith-like, with at least three (pseudo) 'shields' (e.g. Thierstein, 1974: pl.7, figs 6, 8). The tiered nature is produced by lateral protrusions from the outer cycle of the loxolith wall.
The V-unit cycle dominates the rim, resulting in a largely dark image in xpl. It is formed of an inner and outer cycle,the outer cycle forms the tiers visible in side view, and the flange of Kamptnerius. The inner cycle extends inward to meet the central area elements. A thin cycle of R-units, occurs between the two V-unit cycles and is seen as a peg-like cycle in proximal view (described as a "beaded crown" by Perch-Nielsen 1985) but does not extend to the distal surface, separate inrr and outer rim it is this cycle which creates the distinctive bright median-cycle in xpl.
Search data:
: placolith,
Lith 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 ranges of the species in this database First occurrence (base): within Late Aptian Substage (112.95-122.98Ma, base in Aptian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: this is a higher taxon page so Neptune data is not plotted. For the customisable plot option go to a genus page Parent: Arkhangelskiales
References:
Bown, P. R. & Young, J. R. (1997). Mesozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 21-36. gs
Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Lower Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 86-131. gsO
Deflandre, G. (1959). Sur les nannofossiles calcaires et leur systématique. Revue de Micropaléontologie. 2: 127-152. gs
Thierstein, H. R. (1974). Calcareous nannoplankton - Leg 26, Deep Sea Drilling Project. Initial Reports of the Deep Sea Drilling Project. 26: 619-667. gs
Young, J. R. & Bown, P. R. (1997). Proposals for a revised classification system for calcareous nannoplankton. Journal of Nannoplankton Research. 19(1): 15-47. gs
Kamptneriaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 6-12-2023
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