Distinguishing features:
Parent taxon (Podorhabdales): Placolith (or modified placolith) coccoliths showing little or no imbrication. Typically, V-units form distal shield, R-units form proximal shield.
This taxon: Regular placoliths; rim broad, central area relatively narrow, with variable central structures.
The distal shield is formed from V-units and the proximal shield and tube cycle are formed from R-units.
Daughter taxa (time control age-window is: 0-800Ma)![]() | Granddaughter taxa | ||||
Main genera | |||||
![]() | Biscutum Elliptical 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). | B. constans B. ellipticum B. coronum B. dekaenelii B. magnum B. melaniae B. arrogans B. asymmetricum B. boletum B. dissimilis B. zulloii B. hattneri B. notaculum B. virginica B. gaultensis B. thurowii B. davyi B. depravatum B. dorsetensis B. dubium B. erismatum B. grande B. intermedium B. planum B. profundum B. sp. | |||
![]() | ![]() | ![]() | ![]() | Discorhabdus Circular, shields broad, usually without a prominent inner tube cycle; central-area typically narrow, may contain a spine. | |
![]() | ![]() | ![]() | ![]() | Similiscutum Subcircular-elliptical with smooth, grey appearance in XPL and a narrow, bright inner-cycle; central-area narrow and may be empty or spanned by an axial cross. | |
Gnera with distinctive structures | |||||
![]() | ![]() | ![]() | Boletuvelum Asymmetric base, with large, hollow, flaring spines, closed distally by a domed covering | ||
Chiastella Elliptical, minute with diagonal cross suporting a hollow spine | |||||
![]() | ![]() | ![]() | ![]() | Crucibiscutum Elliptical with prominent, birefringent, axial cross. | |
![]() | ![]() | ![]() | ![]() | Gaarderella Elliptical, large with broad shields; central area wide, spanned by a granular plate. | |
![]() | ![]() | ![]() | Gephyrobiscutum Elliptical with unicyclic rim; central-area spanned by oblique transverse bar with two distal spikes | ||
Helicorhabdus Circular with proximal shield wider than distal; spine with helical structure | |||||
Jimenezberrocosoia Elliptical with slits between shield elements and axial cross | |||||
![]() | ![]() | ![]() | Seribiscutum Elliptical with central-area spanned by broad platelets. | ||
![]() | ![]() | ![]() | ![]() | Sollasites Elliptical with relatively wide central-area spanned by complex structure | S. arctus S. arcuatus S. bipolaris S. concentricus S. falklandensis S. horticus S. lowei S. pristinus S. thiersteinii S. sp. |
Taxonomy:
Farinacci & Howe catalog pages: Biscutaceae [no catalog entry yet]
Distinguishing features:
Parent taxon (Podorhabdales): Placolith (or modified placolith) coccoliths showing little or no imbrication. Typically, V-units form distal shield, R-units form proximal shield.
This taxon: Regular placoliths; rim broad, central area relatively narrow, with variable central structures.
The distal shield is formed from V-units and the proximal shield and tube cycle are formed from R-units.
Morphology:
Size:
Tags | LITHS: placolith, |
Metrics | Lith size: 0->0µm; |
Geological Range:
Last occurrence (top): at top of Thanetian Stage (100% up, 56Ma, in Thanetian stage). Data source: Total of range of species in this database
First occurrence (base): in mid part of Sinemurian Stage (47% up, 195.3Ma, in Sinemurian stage). Data source: Total of range of species in this database
Plot of occurrence data:
Black, M. (1971a). Coccoliths of the Speeton Clay and Sutterby Marl. Proceedings of the Yorkshire Geological Society. 38: 381-424. 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 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. (1998a). Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. 1-328. gs O Bukry, D. (1969). Upper Cretaceous coccoliths from Texas and Europe. University of Kansas Paleontological Contributions, Articles. 51 (Protista 2): 1-79. gs O 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 O Noël, D. (1965b). Sur les Coccolithes du Jurassique Européen et d'Afrique du Nord. Essai de classification des coccolithes fossiles. Éditions du Centre National de la Recherche Scientifique, Paris. 1-209. gsReferences:
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Biscutaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 23-5-2022
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10065 Go to Archive.is to create a permanent copy of this page - citation notes |
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