Biscutum


Classification: Coccolithophores -> Mesozoic Survivors -> Biscutaceae -> Biscutum
Sister taxa: Biscutum

Daughter taxa: (blue => in age window 0-800Ma)
Biscutum braloweri
Coccoliths medium-sized, central area closed or with narrow opening, coccospheres ovoid to ellipsoidal
Biscutum castrorum

Biscutum harrisonii
Medium sized, broadly elliptical, bicyclic placolith with a closed central area. The birefringent tube cycle is narrow but conspicuous in XPL.
Biscutum neocoronum
Species of Biscutum? with a relatively broad distal shield and a small central area characterized by a bright outer ring in phase contrast and polarized light. The inner portion of the central area is dark in phase contrast.
Biscutum sp.
Specimens which cannot be assigned to any established species

Taxonomy:

Citation: Biscutum Black in Black and Barnes, 1959
Rank: Genus
Type species: Biscutum testudinarium Black, 1959
Synonyms: Palaeopontosphaera Noël, 1965
Taxonomic discussion: Biscutum coccoliths with a small central area filled by a bright plug are a characteristic component of Early Palaeocene assemblages as noted by many autohrs (e.g Romein 1979, Pospichal 1996). There is, however, not much agreement on species names. Names based on Danian specimens include Biscutum panis (Edwards 1973) and Biscutum harrisonii Varol 1989,  names based on Cretaceous holtypes inlcude Biscutum castrorum Black 1959 and B. melaniae (Gorka 1957), but both these have very poorly illustrated holotypes from significantly oldersediments which may represent other species. 
B. neocoronum and B. braloweri may represent separate species.

Distinguishing features: Elliptical placoliths with broad shields with or without a prominent inner tube cycle; the central-area may be imperforate or narrow and vacant or spanned by a simple structure (plate, cross or bar).

Farinacci & Howe catalog pages: Biscutum + + + * , Palaeopontosphaera + + + + *

Search data:
TagsLITHS:
MetricsLith size: 3->10µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): in lower part of Lutetian Stage (23% up, 46.3Ma, in Lutetian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Berriasian Stage (0% up, 145Ma, in Berriasian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Black, M. & Barnes, B. (1959). The structure of Coccoliths from the English Chalk. Geological Magazine. 96(5): 321-328. gs

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

de Kaenel, E. & Bergen, J. A. (1993). New Early and Middle Jurassic coccolith taxa and biostratigraphy from the eastern proto-Atlantic (Morocco, Portugal and DSDP Site 547B). Eclogae Geologicae Helvetiae. 86(861-907): -. gs V O

Edwards, A. R. (1973). Key species of New Zealand calcareous nannofossils. New Zealand Journal of Geology and Geophysics. 16: 68-89. gs

Górka, H. (1957). Les Coccolithophoridés du Maestrichtien supérieur de Pologne. Acta Palaeontologica Polonica. 2: 239-284. gs V O

Noël, D. (1965b). Sur les Coccolithes du Jurassique Européen et d'Afrique du Nord. Éditions du Centre National de la Recherche Scientifique, Paris. 1-209. gs

Pospichal, J. J. (1996d). High latitude calcareous nannofossil changes at the Cretaceous/Tertiary boundary in the southern Indian Ocean. In, Moguilevsky, A. & Whatley, R. (eds) Microfossils and Oceanic Environments. University of Wales, Aberystwyth-Press 205-229. gs

Romein, A. J. T. (1979). Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletin. 22: 1-231. gs V O


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Biscutum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 29-11-2020

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=80 Go to Archive.is to create a permanent copy of this page - citation notes



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