Distinguishing features: Small, normally elliptical Biscutum with narrow central area. Bicyclic image in XPL.
Taxonomy:
Farinacci & Howe catalog pages: Palaeopontosphaera dubia + + + * , Discorhabdus longicornis *
Distinguishing features: Small, normally elliptical Biscutum with narrow central area. Bicyclic image in XPL.
Morphology remarks: This name is primarily used in the Jurassic, but small Biscutum coccoliths are also a common feature of Cretaceous assemblages, where they tend to be called B. constans or B. ellipticum.
Geological Range:
Last occurrence (top): within Berriasian Stage (139.39-145.01Ma, top in Berriasian stage). Data source: Bown & Cooper 1998
First occurrence (base): within Early Toarcian Substage (178.24-182.70Ma, base in Toarcian stage). Data source: Bown & Cooper 1998
Plot of occurrence data:
Barnard, T. & Hay, W. W. (1974). On Jurassic coccoliths: A tentative zonation of the Jurassic of Southern England and North France. Eclogae Geologicae Helvetiae. 67(3): 563-585. 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. (1987a). Taxonomy, evolution, and biostratigraphy of Late Triassic-Early Jurassic calcareous nannofossils. Special Papers in Palaeontology. 38: 118-. gs Crux, J. A. (1987b). Early Jurassic calcareous nannofossil biostratigraphic events. Newsletters on Stratigraphy. 17: 79-100. gs Crux, J. A. (1987a). Concerning dimorphism in Early Jurassic coccoliths and the origin of the genus Discorhabdus Noël 1965. Abhandlungen der Geologischen Bundesanstalt. 39: 51-55. 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 de Kaenel, E. & Bergen, J. A. (1996). Mesozoic calcareous nannofossil biostratigraphy from sites 897, 899, and 901, Iberia Abyssal Plain: New biostratigraphic evidence. Proceedings of the Ocean Drilling Program. Scientific Results. 149: 27-59. gs Grün, W. & Zweili, F. (1980). Das kalkige Nannoplankton der Dogger-Malm-Grenze im Berner Jura bei Liesberg (Schweiz). Jahrbuch der Geologischen Bundesanstalt. 123: 231-341. gs Grün, W., Prins, P. & Zweili, F. (1974). Coccolithophoriden aus dem Lias epsilon von Holzmaden (Deutschland). Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. 147: 294-328. gs Medd, A. W. (1979). The Upper Jurassic coccoliths from the Haddenham and Gamlingay boreholes (Cambridgeshire, England). Eclogae Geologicae Helvetiae. 72: 19-109. gs Noël, D. (1965). Sur les Coccolithes du Jurassique Européen et d'Afrique du Nord. Éditions du Centre National de la Recherche Scientifique, Paris. -. gs Noël, D. (1973). Nannofossiles calcaires de sédiments jurassiques finement laminés. Bulletin du Muséum National d'Histoire Naturelle. 3e serie, 75: 95-156. gs Rood, A. P., Hay, W. W. & Barnard, T. (1971). Electron Microscope Studies of Oxford Clay Coccoliths. Eclogae Geologicae Helvetiae. 64: 245-272. gs Rood, A. P., Hay, W. W. & Barnard, T. (1973). Electron microscope studies of Lower and Middle Jurassic coccoliths. Eclogae Geologicae Helvetiae. 66: 365-382. gs Varol, O. & Girgis, M. (1994). New taxa and taxonomy of some Jurassic to Cretaceous calcareous nannofossils. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. 192: 221-253. gs Wise, S. W. (1983). Mesozoic and Cenozoic calcareous nannofossils recovered by DSDP Leg 71 in the Falkland Plateau region, Southwest Atlantic Ocean. Initial Reports of the Deep Sea Drilling Project. 71: 481-550. gsReferences:
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Biscutum dubium compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 9-12-2019
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