• Crenalithus - the genus Crenalithus has often been used as a synonym of small Reticulofenestra in modern and Quaternary studies. However, the holotype of the type species, Coccolithus doronicoides Black & Barnes 1961 is a proximal view of Gephyrocapsa oceanica (see Young 1998, Jordan & Young 1990).
• Apertapetra Hay, Mohler & Wade, 1966
• Stradnerius Haq, 1968 (type species D. dictyodus)
• Ericsoniella Krhovsky, 1979 - synonym of Cribrocentrum and so Reticulofenestra
• Praenoelaerhabdus Mihajlovic 1993
• Nannoserratolithus Martini & Schiller 1998 - etched Reticulofenestra [my interpretation - JRY 2021]

• Dictyococcites Black, 1967 - like Reticulofenestra but with closed central-area. [NB Objectively Dictyococcites is a junior synyom of Reticulofenestra since the type secies D. danicus does not have a closed central area, so a new generic name should be proposed if this morphotype is distinguished] (= R. bisecta group here)
• Cribrocentrum Perch-Nielsen 1971 - like Reticulofenestra but circular to sub-circular with a robust grill in the central area (= R. reticulata group here)

Subdivision of the genus is notoriously problematic, numerous species names have been proposed and species concepts vary widely between authors. Some distinctive groups can be recognised but many taxa are separated on arbitrary criteria such as size. In consequence it is good practice for authors to clearly define their adopted species concepts in all publications.

Here we distinguish six groups of species. The C. floridanus, R. bisecta, R. lockeri and R. reticulata groups are distinctive sets of species which are rather readily distinguished on straightforward criteria - and indeed have been regarded as separate genera by some authors. The remaining species are all elliptical reticulofenestrids with central openings. These morphotypes occur from the Eocene to the present day, often at very high abundances. They vary greatly in size, central opening size and grill details (when visible and preserved) and almost certainly numerous different species are included. Subdivision is, however, very problematic. At low to mid-latitudes they are usually much less common in the Late Oligocene and Early Miocene and in consequence different species names are usually used before and after this interval, i.e in the Eocene to Early Oligocene and in the Middle Miocene to Pliocene. So, we have separated the species from these two periods, as the R. umbilicus and R. pseudoumbilicus groups.

Extant species the species R. parvula has now been transferred to Gephyrocapsa since it is very closely related to G. ericsonii and so only indirectly related to the fossil Reticulofenestra. This leaves R. sessilis as the only extant species and this is a rather rare and very unusual taxon with a symbiotic relationship with a diatom. 

References: