Nannotax3 - ntax_mesozoic - Cyclagelosphaera argoensis

Distinguishing features:
Parent taxon (Cyclagelosphaera): Circular watznaueriacean coccoliths.
This taxon: A large, concavo-convex species of Cyclagelosphaera (6-11 µm) having a broad, distal shield inner cycle and a small central perforation.

Citation: Cyclagelosphaera argoensis Bown, 1992

C. argoensis is distinguished from other species of Cyclagelosphaera by its large size; convexity; and broad, blocky, distal inner cycle. The structure of the distal inner cycle is distinctive when observed in light microscope and distinguishes this species from other large forms, such as Cyclagelosphaera deflandrei.

Geological Range:
Last occurrence (top): within Hauterivian Stage (130.77-133.88Ma, top in Hauterivian stage). Data source: [PRB rough estimate]
First occurrence (base): in mid part of NJT16a subzone (50% up, 148.1Ma, in Tithonian stage). Data source: Casellato 2010, fig16 - secondary marker

References:

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 O

Bown, P. R. (1992). New calcareous nannofossil taxa from the Jurassic/Cretaceous boundary interval of Sites 765 and 261, Argo Abyssal Plain. Proceedings of the Ocean Drilling Program, Scientific Results. 123: 369-379. gs V 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

Casellato, C. E. (2010). Calcareous nannofossil biostratigraphy of Upper Callovian - Lower Berriasian successions from the Souhern Alps, North Italy. Rivista Italiana di Paleontologia e Stratigrafia. 116(3): 357-404. gs O

Cyclagelosphaera argoensis

References:

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