Nannotax3 - ntax_mesozoic - Rhagodiscus achlyostaurion

Distinguishing features:
Parent taxon (Rhagodiscus): Loxolith coccoliths with low rim and central-area filled by a granular plate which may be perforate and/or spine-bearing. In xpl the rim is unicyclic moderately bright, the central area is granular, lacking a clear extinction cross.
This taxon: Small (4-6µm) Rhagodiscus with relatively narrow central area spanned by a granular plate bearing large spine/spine base. The rim image is distinctly dark in XPL.

Citation: Rhagodiscus achlyostaurion (Hill, 1976) Doeven, 1983

Basionym: Parhabdolithus achlyostaurion Hill, 1976

Synonyms:

Rhagodiscus achylostaurion (Hill, 1976) Doeven, 1983 - incorrect spelling that is sometimes seen

Abut 4-6 µm - Hill (1976) described the species as <5µm long but published images include specimens up to at least 6 µm, and this seems to be a discrete species rathe than an artifcial size defined grouping. [my interpretation - JRY 2020]

Geological Range:
Notes: Bown et al. 1998 (fig 5.2) record the base of "R. achylostaurion" near the top of CC6 but the base of true R. achlyostaurion at the base of NC7B/within CC7B
Last occurrence (top): within Coniacian Stage (85.70-89.39Ma, top in Coniacian stage). Data source: Bown et al. 1998
First occurrence (base): in upper part of CC6 zone (80% up, 122.3Ma, in Barremian stage). Data source: Bown et al. 1998 (fig 5.2)

References:

Bown, P. R. (2005c). Early to Mid-Cretaceous Calcareous Nannoplankton from the Northwest Pacific Ocean, Leg 198, Shatsky Rise. Proceedings of the Ocean Drilling Program, Scientific Results. 198: 1-82. gs O

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. gs O

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

Crux, J. A. (1980). A biostratigraphical study of Upper Cretaceous nannofossils from South-east England and North France. PhD thesis, University College London. -. gs

Doeven, P. H. (1983). Cretaceous nannofossil stratigraphy and paleoecology of the Canadian Atlantic Margin. Bulletin of the Geological Survey of Canada. 356: 1-70. gs

Gale, A. S., Kennedy, W. J., Burnett, J. A., Caron, M. & Kidd, B. E. (1996). The Late Albian to Early Cenomanian succession at Mont Risou, near Rosans (Drôme, SE France): an integrated study (ammonites, inoceramids, planktonic foraminifera, nannofossils, oxygen and carbon isotopes). Cretaceous Research. 17: 515-606. gs

Gale, A. S. et al. (2011). The uppermost Middle and Upper Albian succession at the Col de Palluel, Hautes-Alpes, France: An integrated study (ammonites, inoceramid bivalves, planktonic foraminifera, nannofossils, geochemistry, stable oxygen and carbon isotopes, cyclostratigraphy). Cretaceous Research. 32: 59-130. gs

Hill, M. E. (1976). Lower Cretaceous calcareous nannofossils from Texas and Oklahoma. Palaeontographica Abteilung B Palaeophytologie. 156: 103-179. gs

Kanungo, S., Bown, P. R. & Gale, A. S. (2020). Cretaceous (Albian-Turonian) calcareous nannofossil biostratigraphy of the onshore Cauvery Basin, southeastern India. Cretaceous Research. 118 [2021]: 1-22. gs

Kennedy, W. J. et al. (2000). Integrated stratigraphy across the Aptian-Albian boundary in the Marnes Bleues, at the Col de Pre _-Guittard, Arnayon (Drome), and at Tartonne (Alpes-de-Haute-Provence), France: a candidate Global Boundary Stratotype Section and Boundary Point for the base of the Albian Stage. Cretaceous Research. 21: 591-720. gs

Püttmann, T. & Mutterlose, J. (2019). Calcareous nannofossils from a Late Cretaceous nearshore setting. Journal of Nannoplankton Research. S4: 81-88. gs

Püttmann, T., Mutterlose, J., Kaplan, U. & Scheer, U. (2019). Reworking of Cenomanian ammonites decoded by calcareous nannofossils (southern Münsterland Basin, northwest Germany). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 291(1): 1-17. gs

Thomsen, E. (1987). Lower Cretaceous calcareous nannofossil biostratigraphy in the Danish Central Trough. Danmarks Geologiske Undersøgelse. 20: 1-89. gs

Rhagodiscus achlyostaurion

References:

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