I am not sure where this discussion belongs, but I chose a forum as opposed to a taxonomic comment, because this is not a taxonomic issue. Or is it?
In the deep-water Gulf of Mexico, we observe a form very similar to Discoaster altus/tristellifer (see link below) with
dual knobs of differing sizes for a short pulse in the Late Miocene
(~NN10A-NN9). However, we cannot seem to reference this taxon to occur
in sediments this old. Nor can we reference a similar form in the Late
Miocene. Are we observing a different taxon or the same? Has anyone
observed this taxon (or similar) older than the Pliocene (especially
Gulf of Mexico)? Any references?

http://www.nannotax.org/content/discoaster-altus