Asapholithos neoanfractus

Asapholithos neoanfractus Varol, in prep.

Calculites anfractus Jakubowski (1986) - sensu Schueth & Lees, 2019

The four segments in the central area are separated by zigzag-shaped diagonal sutures and surrounded by a narrow wall. A distal process is absent.

From Greek neo, meaning new and anfractus

The segments and the wall exhibit a white interference colour; therefore, its assignment to Asapholithus is questionable.

Asapholithos neoanfractus superficially resembles Asapholithos anfractus, but it is distinguished by its white interference colour, whereas Asapholithos anfractus exhibits a grey interference colour (in constant extinction, due to the optic axis/c-axis being vertical to the microscope stage). Additionally, A. neoanfractus occurs in Early Turonian to Early Coniacian sediments, while Asapholithos anfractus is restricted to the earliest Cenomanian to Late Albian.

Asapholithos neoanfractus has an overlapping stratigraphic range with Calculites axosuturalis, but it differs in having diagonal sutures without a distal process, whereas Calculites axosuturalis shows nearly axial sutures with a distal process.

Bralower, T. J. & Bergen, J. A. 1998. Cenomanian–Santonian calcareous nannofossil biostratigraphy of a transect of cores drilled across the Western Interior Seaway. In: Dean, W. E. & Arthur, M. A. (Eds.) Stratigraphy and paleoenvironments of the Cretaceous Western Interior Seaway. SEPM Concepts in Sedimentology and Paleontology. 59–77.

Jakubowski, M., 1986. New calcareous nannofossil taxa from the Lower Cretaceous of the North Sea. INA Newsletter. 8, 38-42.

Schueth, J. D., Lees, J. A., 2019. Pioneer nannofossil assemblages from the initial transgression of the Niobrara seaway in the Turonian, San Juan Basin, New Mexico, USA. Marine Micropaleontology 151, 1-12.