The taxonomy of Radiolaria, a subclass within the phylum Protozoa, was developed by Ernest Haeckel in the late 1800s. That classification was based primarily on gross geometric patterns which have been subsequently shown to be unsatisfactory. Reclassification research has been concentrated on the Nassellarian (conical) radiolaria because of more pronounced characters. Spumellarian (spherical) radiolaria, however, have not been regrouped mainly because their morphology is more subtle and difficult. However, they are the most robust and most persistent in the fossil record (Ordovician to present), and therefore the likliest to be preserved in strata.

Two core sites, 77B and 289 from the Deep Sea Drilling Project, provide a continuous time sequence during the Miocene and both probably represent a stable equatorial current system. Slides were made at 1-m intervals from the cores and spumellaria individuals were studied from successive time sequences. Nineteen characters were recorded for each and then subjected to a rigorous analytical technique provided by a numerical taxonomy program (NTPAC-11). Pearson's correlation coefficients detected 23 species throughout the Miocene. An unweighted pair group clustering method using arithmetic averages grouped these species into 14 genera.

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