"Colymboides", the oldest unequivocal gaviiform genus known as of 2009, is widely known from early Priabonian – about 37 million years ago (Ma) in the Late Eocene – to Early Miocene (late Burdigalian, less than 20 Ma) limnic and marine rocks of western Eurasia north of the Alpide belt, between the Atlantic and the former Turgai Sea. It is usually placed in the Gaviidae already, but usually in a subfamily Colymboidinae, with the modern-type loons making up the "Gaviinae". But the "Colymboides" material is generally quite distinct from modern loons, and may actually belong in a now-extinct family of primitive gaviiforms.