Tonromeinia noeliae

Tonromeinia noeliae Bowman & Varol, 2021

A gigantic elliptical species of Tonromeinia possessing two discs and a column, all of which are similar in diameter and height/thickness. A wide oval opening dominates the central area, lacks a tube cycle, and appears featureless.

In honour of renowned French nannofossil specialist Prof. Dr D. Noel, seasoned nannofossil taxonomist and biostratigrapher.

Overall length: 12.56μm; Overall width: 11.16μm; Central Opening width: 3.82μm; Central Opening length: 5.51μm; Discs/Column width: 3.48μm.

Very large (>11.0μm) elliptical form consisting of two discs, a column and a featureless central area without a tube cycle. In the side-view, the discs and a column have similar diameters and heights/thicknesses. The width of the central opening is often slightly greater than the width of the discs/ column. The overall elliptical shape and large central opening are essential criteria for identifying this species. Tonromeinia noeliae is most commonly observed in plan-view because the low columnar habit of the species produces a mass concentration along the horizontal (width) axis, which compels specimens to settle in plan-view.

Under cross-polarised light, the distal side displays dextrogyre extinction lines, whereas the proximal side exhibits a laevogyre extinction line. Observed utilising a gypsum plate, alignment of the horizontal axis and blue region signifies the distal side. Still, the equal orientation of the vertical axis and blue section corresponds with the proximal side. The discs and a column are birefringent in side-view and plan-view, displaying yellowish birefringence colour in plan-view and yellowish-brownish-reddish birefringence colours in side-view.

Tonromeinia noeliae displays a considerable overall size (>11.0μm) and has relatively wider discs/a column than Tonromeinia deflandrei. Tonromeinia noeliae appears elliptical, whereas Tonromeinia deniseae is circular.

Bowman, A. R. & Varol, O. 2021. A Taxonomic Revision of Heliolithaceae - Applications in Resolving the Problematic Calcareous Nannofossil Biostratigraphy of the Paleocene. In: M. Montenary, M. (Ed.). Calcareous nannofossil biostratigraphy of the Stratigraphy and timescales. 6: 43-223.