Nannotax3 - ntax_cenozoic - Umbilicosphaera jordanii

Citation: Umbilicosphaera jordanii Bown, 2005

Taxonomic discussion: Broader shields than Umbilicosphaera bramlettei and Coronocyclus nitescens. Comparable in general morphology to Calcidiscus protoannulus but less birefringent shield appearance and bright tube cycle is less well defined in XPL. In addition, the extinction lines crossing the tube cycle are near-axial in C. protoannulus and near-diagonal in U. jordanii.

Distinguishing features:
Parent taxon (Umbilicosphaera): Central area open
This taxon: Medium sized (3.5-6.0 µm) circular ring-shaped placoliths with a non-birefringent distal shield, a narrow bright tube cycle crossed by non-axial extinction lines, and vacant central area that is slightly wider than the shields.

Geological Range:
Last occurrence (top): within NP23 zone (29.62-32.02Ma, top in Rupelian stage). Data source: Bown et al., 2007
First occurrence (base): within NP4 zone (61.51-63.25Ma, base in Danian stage). Data source: [PRB rough estimate]

References:

Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs O

Bown, P. R. (2005d). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research. 27(1): 21-95. gs O

Bown, P. R. (2010). Calcareous nannofossils from the Paleocene/Eocene Thermal Maximum interval of southern Tanzania (TDP Site 14). Journal of Nannoplankton Research. 31(1): 11-38. gs O

Bown, P. R. (2016). Paleocene calcareous nannofossils from Tanzania (TDP sites 19, 27 and 38). Journal of Nannoplankton Research. 36(1): 1-32. gs O

Bown, P. R., Dunkley-Jones, T. & Young, J. R. (2007). Umbilicosphaera jordanii Bown 2005 from the Paleogene of Tanzania: confirmation of generic assignment and a Paleocene origination for the family Calcidiscaceae. Journal of Nannoplankton Research. 29(1): 25-30. gs

Dunkley Jones, T., Bown, P. R. & Pearson, P. (2009). Exceptionally well preserved upper Eocene to lower Oligocene calcareous nannofossils (Prymnesiophycidae) from the Pande Formation (Kilwa Group), Tanzania. Journal of Systematic Palaeontology. 7(4): 359-411. gs

Jones, A. P. & Dunkley Jones, T. (2020). Middle Eocene to Early Oligocene calcareous nannofossils from the Nanggulan Formation, Java, Indonesia. Journal of Nannoplankton Research. 38(1): 57-79. gs

Shamrock, J. L. & Watkins, D. K. (2012). Eocene calcareous nannofossil biostratigraphy and community structure from Exmouth Plateau, Eastern Indian Ocean (ODP Site 762). Stratigraphy. 9(1): 1-11. gs

Umbilicosphaera jordanii

References:

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