Pontosphaera erythrathalassanica

Pontosphaera erythrathalassanica Varol, 2025a

Species of Pontosphaera have low walls and a distal cover approximately equal in height to the proximal plate, resulting in nearly uniform interference colours in plan view under XPL. The proximal plate features tiny pores arranged in approximately ten transverse patterns.

Derived from the Greek Erythrá Thálassa (Red Sea), referring to the type area

Length = 10.70 μm; Width = 8.00 μm (both measured in PC).

Optical Properties: The proximal plate and outer wall remain in constant extinction, while the inner wall and distal cover over the proximal plate display first-order white interference colours, laevogyre-inclined extinction lines with a typical extinction angle of approximately 68°, and length-fast (−) elongation on the distal side.

Pontosphaera erythrathalassanica is distinguished from Pontosphaera lepida by the absence of a flange (flaring) at the distal end. It differs from Pontosphaera paynei by having an almost equal-height wall and distal cover, making it difficult to separate the wall from the central area. In contrast, Pontosphaera paynei has a higher wall and a very thin distal cover, allowing for easier differentiation of the wall from the central area based on interference colours.

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