Reticulofenestra dennei

Reticulofenestra dennei Varol, 2025

Cyclicargolithus minutus Denne, 2008 (nom. nud.) Invalid ICN Art. 38.1

Reticulofenestra dennei is a small species, measuring between 3.0 and 5.0 μm. It is strictly circular, with a void central area narrower than the width of the pelaga (the surrounding structure). The tube cycle around the central area is smooth and narrow.

In honour of Prof. Dr R. Denne, Hunter Enis Endowed Chair in Geology, Austin, TX, USA, in recognition of his contributions to taxonomy and biostratigraphy of calcareous nannofossils.

Maximum diameter = 4.76 μm; Diameter of central area = 1.40 μm; Width of the pelage = 1.68 μm.

Optical Properties: The shields display first-order greyish-white interference colours. Reticulofenestra dennei shows inclined dextrogyre (right-handed) extinction lines on the tube cycle but exhibits parallel extinction lines on the shields. These angles are typically 0° on the distal shield and about 77° on the tube cycles on the distal side. The species has a length-fast (-) elongation. The extinction angle on the shield is distinctly different from those typically seen in the genera Reticulofenestra and Cyclicargolithus, raising questions about its assignment to Reticulofenestra.

Reticulofenestra dennei differs from Reticulofenestra pospichalii by having a narrower central opening than the width of the pelaga, whereas Reticulofenestra pospichalii has a wider central opening than the width of the pelaga. Reticulofenestra dennei is smaller than Reticulofenestra bukryi (synonym Reticulofenestra kahniae), which has a size range from 6.0 to 8.0 μm according to Wise, 1973 (calculated holotype size is 6.8 μm).

Denne, R. A., (2008): Utilizing abundance changes of new and non-standard calcareous nannofossil taxa to increase biostratigraphic resolution in expanded continental margin deposits: Examples from the Middle and Lower Miocene of the Gulf of Mexico. - Transactions of the Gulf-Coast Association of Geological Societies. 58: 227-239.

Hay, W. W., Mohler, H. P. & Wade, M. E., (1966): Calcareous nannofossils from Nal'chik (northwest Caucasus). - Eclogae Geologicae Helvetiae. 59: 379-399.

Wise, S. W., (1973): Calcareous nannofossils from cores recovered during Leg 18, Deep Sea Drilling Project: biostratigraphy and observations on diagenesis. - Initial Reports of the Deep Sea Drilling Project. 18: 569-615.