Nannotax3 - ntax_mesozoic - Arkhangelskiella

Nannotax3 - ntax_mesozoic - Arkhangelskiella Nannotax3 - ntax_mesozoic - Arkhangelskiella

Arkhangelskiella

Classification: ntax_mesozoic -> Arkhangelskiales -> Arkhangelskiellaceae -> Arkhangelskiella
Sister taxa: Arkhangelskiella, Broinsonia, Thiersteinia

Distinguishing features:
Parent taxon (Arkhangelskiellaceae): Arkhangelskielids with shields predominantly formed of R-units, thus bright in cross-polarised light; V-units often form dark outer rim.
This taxon: R-units cover the distal surface, so coccolith appears bright, unicyclic, in LM (although darker towards outer edge); central-area has perforate plate with axial sutures. 4 tiers visible in side view.

Daughter taxa (time control age-window is: 0-800Ma)
				Arkhangelskiella maastrichtiensis Large to very large (>10µm) with a broad rim (>1.5µm)
				Arkhangelskiella cymbiformis Large (8-10µm), with a narrow rim (<1.5µm)
				Arkhangelskiella confusa Small to medium sized (4-8µm), with a <1.5µm thick rim
				Arkhangelskiella specillata Like A. cymbiformis but with >5 perforations per quadrant (Verbeek 1977)
				Arkhangelskiella sp. Specimens not identified to species level

Taxonomy:

Citation: Arkhangelskiella Vekshina, 1959

taxonomic rank: Genus

Type species: Arkhangelskiella cymbiformis Vekshina, 1959

Taxonomic discussion: The typcial species is A. cymbiformis. Other species have been described based on numbers of pores (A. specillata, A. pauciperforata) or rim width (A. maastrichtiensis. A. confusa). None of these species, however, are well supported and they all appear to intergrade with A. cymbiformis. Linnert & Mutterlose (2009) investigated Arkhangelskiella size varation in the Campanian and Maastrichtian and concluded that only one species was present - but there is a well docuemented trend toward larger size through time.

Farinacci & Howe catalog pages: Arkhangelskiella + + + + *

Morphology:

The most common genus and a characteristic component of Maastrichtian nannofossil assemblages. The central area structure is described in detail by Moshkovitz and Osmond (1989).
Ditinction from Broinsoinia:
- in LM the entire cocclith rim is brightly birefringent (vs there being a distinct dark outer cycle in Broinsoinia)
- in SEM in distal view, a single cycle of elements, typically with clear sutures, covers the distal surface (vs inner and outer cycles in Broinsonia).
- in SEM in side view, four tiers of elements are visible (vs 3 in Broinsonia).
- in SEM in proximal view, they are essentially identical.

Search data:

LITHS: placolith, elliptical, CA: plate, pores, closed, CROSS-POLARS: rim-unicyclic, R-prominent,

Lith size: 5->20µm;
Data source notes: size range of included species

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 Campanian Stage (72.17-83.65Ma, base in Campanian 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. See also: customisable plot Parent: Arkhangelskiellaceae

References:

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

Linnert, C. & Mutterlose, J. (2009a). Biometry of the Late Cretaceous Arkhangelskiella group: ecophenotypes controlled by nutrient flux. Cretaceous Research. 30: 1193-1204. gs

Moshkovitz, S. & Osmond, K. (1989). The optical properties and microcrystallography of Arkhangelskiellaceae and some other calcareous nannofossils of the Late Cretaceous. In, Crux, J. A. & van Heck, S. E. (eds) Nannofossils and their applications: Proceedings of the 2nd INA Conference, London 1987. British Micropalaeontological Society Publication Series . 76-97. gs O

Vekshina, V. N. (1959). Coccolithophoridae of the Maastrichtian deposits of the West Siberian lowlands. Trudyi Instituta Geologii i Geogiziki, Sibiriskoe Otlodelenie, Akademiya Nauk SSSR (Nauka) Moscow. 2: 56-81. gs