Reptilian Phonology

[vergil]

The key here being the labials.

I have a species of sapient dinosaurian reptiles and I've been working on how the phonologies of their languages should be set up. In regards to the structure of their mouths, I've more or less set on the species having overall similar structure to the human mouth (though perhaps longer), but with unmuscled lips.

I've tried experimenting a bit with my own mouth to see how not being able to move my lips might affect speech, but there seem to be a few gray areas in what is and what isn't possible.

Labialized and rounded sounds should be impossible. Labiodental sounds also seem to be out. /m/ is possible. But I'm not sure about bilabial sounds (/p/, /b/, &c, not including the trill). I think I can produce the plosives and fricatives without using my lips' muscles, but I'd prefer some additional views on this.

Thoughts?

[mèþru]

There was really great thread on the phonological constraints of squamate biology back in 2016 but I can't find it.
If no one else has a copy, I'll try to come up with what I can remember.