Zygodiscus? pseudanthophorus Bramlette & Martini, 1964
Optical Properties: In the plan view, the outer wall exhibits a vertical optic axis relative to the microscope stage; therefore, it appears in constant extinction (dim). The wider inner wall and the complex transverse bar exhibit whitish-yellow to yellow interference colours, inclined extinction lines, and length-fast (-) elongation.
The entire species shows whitish-yellow to yellow interference colours in the side view. The outer wall displays length-fast (-) elongation, while the inner wall and distal process display length-slow (+) elongation.
The loxolith calcareous nannofossils consist of a double wall and a central area spanned by a bar with a complex structure, supporting a massive distal process. When observed in a mobile mount, the side view shows that the distally gently widening, fully developed inner wall partly obscures the distally tapering, much narrower outer wall. In contrast, the distally widening outer wall obscures the distally tapering proximal proto-inner wall of Zeugrhabdotus embergeri.
Bramlette, M. N. & Martini, E. 1964. The great change in calcareous nannoplankton fossils between the Maastrichtian and Danian. Micropaleontology. 10(2): 291-322.
Varol, O. & Girgis, M. 1994. New taxa and taxonomy of some Jurassic to Cretaceous calcareous nannofossils. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 192: 221-253.