Nannotax Enabling nannofossil research

I must admit I have had problems with this too. I tried arguing a long time ago (Young 1991) that we ought to get rid of Pseudoemiliania since it intergrades with Reticulofenestra, and the existence of R. asanoi makes it even worse. The best study I know of the group is still Matsuoka and Okada (1989) they used TEM to measure and count specimens, which is a good way to reliably spot the slits and give detailed data on morphotypes in the group in the mid Quatnary from a piston core in subtropical N.W. Pacific.
They defined a Reticulofenestra sp. A , >5µm with no slits and showed that the >6µm examples of this morphotype had a limited range around the Jaramilo magnetochron (C1r.1n), which is the same as R. asanoi sensu e.g. Raffi et al. (2006). Their data also shows that large P. ovata specimens increase in abundance during this interval. So, yes R. asanai will intergrade with smaller oval Reticulofenestra species and with P. ovata specimens with a few slits, but it is still useful to distinguish it.

Matsuoka, H. & Okada, H. 1989. Quantitative Analysis of Quaternary Nanoplankton in the Subtropical Northwestern Pacific Ocean. Marine Micropaleontology 14, 97- 118.

Raffi, I., Backman, J., Fornaciari, E., Palike, H., Rio, D., Lourens, L. J. & Hilgen, F. J. 2006. A review of calcareous nannofossil astrobiochronology encompassing the past 25 million years. Quaternary Science Reviews 25, 3113-3137.

Young, J. R. 1990. Size variation of Neogene Reticulofenestra coccoliths from Indian Ocean DSDP cores. Journal of Micropalaeontology 9, 71-86.