Tillamook language

Tillamook is an extinct Salishan language, formerly spoken by the Tillamook people in northwestern Oregon, United States. The last fluent speaker was Minnie Scovell who died in 1972. In an effort to prevent the language from being lost, a group of researchers from the University of Hawaii interviewed the few remaining Tillamook-speakers and created a 120-page dictionary.

Internal rounding
The so-called "rounded" consonants (traditionally marked with the diacritic ⟨ʷ⟩, but here indicated with ⟨ᵓ⟩), including rounded vowels and ⟨w⟩, are not actually labialized. The acoustic effect of labialization is created entirely inside the mouth by cupping the tongue (sulcalization). Uvulars with this distinctive internal rounding have "a kind of timbre" while "rounded" front velars have  coloring. These contrast and oppose otherwise very similar segments having or  coloring&mdash;the "unrounded" consonants.

is also formed with this internal rounding instead of true labialization, making it akin to. So are vowel sounds formerly written as or, which are best characterized as the diphthong  with increasing internal rounding.