Complex sentence: Most terns were formerly treated as belonging to one large genus "Sterna", with just a few dark species placed in other genera; in 1959, only the noddies and the Inca Tern were excluded from "Sterna".
Split into simpler sentences: Most terns were formerly treated as belonging to one large genus "Sterna", with just a few species in other genera. In 1959, only the noddies and the Inca Tern were excluded from "Sterna".