Nannotax3 - ntax_mesozoic - Wisea sanjuanensis

Citation: Wisea sanjuanensis Lees, Schueth & Howe in Schueth & Lees (2019)

Basionym: Wisea sanjuanensis Lees, Schueth & Howe in Schueth & Lees (2019)

Morphology: A species of Wisea with a very small central opening that is covered by a very small axial cross that appears to sit immediately above it and may indicate a short spine. The arms of the cross are very short, of approximately equal length, and are pointed at the ends.

Differentiation: The axial cross in Wisea is distinct from those in other cretarhabdaceans with axial crosses, being proportionally smaller relative to the rim, and virtually filling the central area. Comment: This taxon may have been logged by other workers as Cretarhabdus johannisbergensis Hoffmann & Vetter, 1971, the holotype of which is a transmission(?) electron micrograph of what appears to be a poorly preserved and partially obscured retecapsid with an indistinct assembly of crystals filling the central area that are not aligned into an axial cross, as suggested by an accompanying line-drawing of presumably the same specimen by those authors. This lack of a central cross, in particular, leads us to believe that sanjuanensis is not johannisbergensis.

Geological Range:
Last occurrence (top): within UC9 zone (89.77-91.78Ma, top in Turonian stage). Data source: Schueth & Lees 2019
First occurrence (base): within UC8 zone (91.78-92.99Ma, base in Turonian stage). Data source: Schueth & Lees 2019

References:

Hoffmann, N. & Vetter, J. (1971). Coccolithen aus der Turonscholle von Johanisberg, nordwestlich von Pasewalk. Geologie, Berlin. 20(10): 1170-1211. gs

Lees, J. A. & Schueth, J. (2020). Taxonomic note – New Upper Cretaceous nannofossil taxa from the Turonian of New Mexico, USA. Journal of Nannoplankton Research. 30(1): 81-82. gs V O

Schueth, J. D. & Lees, J. A. (2019). Pioneer nannofossil assemblages from the initial transgression of the Niobrara seaway in the Turonian, San Juan Basin, New Mexico, USA. Marine Micropaleontology. 151: x-y. gs

Tags	LITHS: placolith, elliptical, CA: cross-axial, ca_disjunct, process, closed, CROSS-POLARS: rim-unicyclic, R-prominent,
Metrics	Lith size: 4->6µm; Data source notes: Holotype +/- 1 µm

Wisea sanjuanensis

References:

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