Prevailing usage followed to avoid double taxon.

Callistethus, with marginatus/a in it, still widely accepted as a genus concept, e.g. here:
https://www.researchgate.net/publication/280841447_The_genus_Callistethus_Coleoptera_Scarabaeidae_Rutelinae_in_the_Neotropics_New_data_and_new_species_from_Costa_Rica
and here:
http://unsm-ento.unl.edu/Guide/Scarabaeoidea/Scarabaeidae/Rutelinae/Rutelinae-Tribes/Anomalini/Anomalini-generic-pages/Callistethus/Callistethus.html
[nearctic part of range = marginatus only]

More discussion on the subject under https://www.inaturalist.org/flags/27712