Wikipedia
Mirandornithes
Mirandornithes (name coined by Sangster (2005)) is a clade that consists of flamingos and grebes. Many scholars use the term Phoenicopterimorphae for the superorder containing flamingoes and grebes.
Determining the relationships of both groups has been problematic. Flamingos had been placed with numerous branches within Neognathae, such as ducks and storks. The grebes had been placed with the loons. However recent studies have confirmed these two branches as sister groups.
Both primitive phoenicopteriformes and their closest relatives, the grebes, were highly aquatic. This indicates that the entire mirandornithe group evolved from aquatic, probably swimming ancestors.