Helenemanivitia colombiana

Helenmanivitia colombiana Varol, 2025a

1977a Cylindralithus serratus Bramlette & Martini, 1964 – Perch-Nielsen, pl. 48, figs. 19, 21; ?non-pl. 48, figs. 17-18, 20.

1998 Cylindralithus serratus Bramlette & Martini, 1964 – Burnett in Bown, pl. 6.4, fig. 30.

A circular loxolith composed of a single protolith wall with approximately 20 segments, a proximal rim extending beyond the wall, and a vacant central area. The wall flares distally, while the rim flares proximally.

Name after Colombia, where the holotype was recovered.

Diameter = 4.15 μm; Diameter of central opening: 1.97 μm; Height = 2.34 μm (all measured in XPL).

Optical Properties: Helenemanivitia colombiana exhibits first-order white interference colours in both plan and side views. This species displays inclined dextrogyre extinction lines, typically at angles around 77°, with length-fast (-) elongation on the distal side.

Helenemanivitia colombiana has been erroneously assigned to Cylindralithus serratus, a taxon characterised by a double wall, by various authors, including Perch-Nielsen (1977a) and Burnett in Bown (1998).

Burnett, J. A. 1998. Upper Cretaceous. In: Bown, P. R. (Ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 132-199.

Perch-Nielsen, K.1977a. Albian to Pleistocene calcareous nannofossils from the Western South Atlantic, DSDP Leg 39. Initial Reports of the Deep Sea Drilling Project. 39: 699-823.

Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222