Perchnielsenella ismailkoselii

Varol, 2025a Jun 16, 2025

Set number: 1973

  • Perchnielsenella ismailkoselii VR 11399 1
  • Perchnielsenella ismailkoselii VR 11396 2
  • Perchnielsenella ismailkoselii VR 11402 3
  • Perchnielsenella ismailkoselii VR 11407 4
  • Perchnielsenella ismailkoselii VR 11398 5
  • Perchnielsenella ismailkoselii VR 11397 6
  • Perchnielsenella ismailkoselii VR 11403 7
  • Perchnielsenella ismailkoselii VR 11408 8
  • Perchnielsenella ismailkoselii VR 11406 9
  • Perchnielsenella ismailkoselii VR 11405 10
  • Perchnielsenella ismailkoselii VR 11404 11
  • Perchnielsenella ismailkoselii VR 11410 12
    10µm
Quebrada La Llana, Colombia

Holotype
Final Epithet
Perchnielsenella ismailkoselii Varol, 2025a
Basionym

Perchnielsenella ismailkoselii Varol, 2025a

Synonyms

Perchnielsenella stradneri (Perch-Nielsen, 1973) Watkins in Watkins & Bowdler, 1984; pp. 664-665, ?pl.5, figs. 5, 6; pl.6, fig. 1-9; pl. 7, figs. 1, 2, 4.

Diagnosis

Strictly circular species in the plan view of Perchnielsenella are characterised by a double-storey, unicyclic wall, with each storey comprising twenty-four to thirty-six strongly sinistrally imbricated segments. The two walls are unequal in height, with their intersection appearing indistinct in light microscopy (LM). At their junction, a double-layered amedian diaphragm is present, positioned securely as its periphery is embedded within the inner cavity of the wall. The walls gradually widen towards their intersection in the side view.

The outer surface of Perchnielsenella ismailkoselii is devoid of ornamentation.

Etymology

In honour of Ismail Köseli, economist, Istanbul, Turkey

Dimensions Of Holotype

Length = 8.46 μm; Maximum Diameter = 6.87 μm; Maximum width of the wall = 3.05 μm; Length of the diaphragm = 3-74 μm; Thickness of the diaphragm = 1.09 μm (both measured in XPL).

Description

Optical Properties: Perchnielsenella ismailkoselii exhibits parallel (straight) extinction with length-fast (-) elongation in the plan view and length-slow (+) elongation in the side view. First-order yellow to second-order blue interference colours are observed, reflecting the significant height and width (retardation colours). This species can settle randomly in either plan or side view due to its similar height-to-width ratio.

Remarks

Perchnielsenella ismailkoselii differs from Perchnielsenella oweinaensis and Perchnielsenella stradneri by the lack of ornamentation on its outer surface. The outer surfaces of the latter species are densely decorated with lateral and longitudinal ornamentation.

References

Varol, O. 2025b. New observation on Paleocene holococcoliths. Neues Jahrbuch für Geologie und Paläontologie,

Watkins, D. K. & Bowdler, J. L. 1984. Cretaceous calcareous nannofossils from Deep Sea Drilling Project Leg 77, southeast Gulf of Mexico. Initial Reports of the Deep Sea Drilling Project. 77: 649-674.

Taxonomy
Perchnielsenella
Biostratigraphy
  • Phanerozoic
    • Mesozoic
      • Cretaceous
        • Late Cretaceous
          • -
            • Maastrichtian
              • Early Maastrichtian
            • Campanian
              • Late Campanian
Stratigraphic Range
Late Campanian - Early Maastrichtian
Age (Ma)
74.47 - 71.02
Zone(s)
CC23
Holotype
Perchnielsenella ismailkoselii VR 11402 Perchnielsenella ismailkoselii VR 11402

Perchnielsenella ismailkoselii Varol, 2025a

Early Maastrichtian

Quebrada La Llana, Colombia