Asinithistimorfi paraxenos Bowman & Varol, 2021
Moderately large (6.0-9.0 µm) and elliptical heliolith comprised two discs and a column. The discs are of unequal diameter (i.e. the median disc is wider than the proximal disc) and appear flat to very slightly convex (observed in side-view). The distal plug appears rough and distinct. The discs and narrow central opening are visible under phase-contrast and bright-field setting (Plate 2, Figs. 20 and 24 in Bowman & Varol, 2021) in plan-view. The column and plug artificially resemble an overgrown Dictyococcites bisectus under polarised light.
Optical properties: In plan-view, the discs are non-birefringent, and the column is strongly birefringent. The entire species appear birefringent in the side-view. . In cross polarised light, the distal side shows a dextrogyre-type extinction pattern (e.g. Pl. 3, Figs. 10. 14 in Bowman & Varol, 2021), whereas the proximal side is characterized by a laevogyre-type extinction pattern (e.g. Pl. 3, Figs. 11, 15 in Bowman & Varol, 2021). When using the gypsum plate, with the species orientated in the north-south position, a distal view will show the blue regions corresponding to the horizontal axis, while a proximal view will show the blue sectors corresponding to the vertical axis.
The elliptical shape and bizarre rough appearance of the column and plug (and unique form of species in general) are diagnostic identification features.
Bowman, P. 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.
Asinithistimorfi aubryae Bowman & Varol, 2021
DSDP Leg 36, Site 327A, The Maurice Ewing Bank, Falkland Plateau